Prolactin

Prolactin at a glance

What is prolactin?

Prolactin is a protein hormone produced by specialised cells in the front section of the pituitary gland, a structure about the size of a pea that sits beneath the brain and directs much of the endocrine system. Its name comes from lactation, and that is genuinely its headline role, though the picture is broader than the name suggests. Prolactin receptors turn up in the breast, the ovaries, the testes, the liver, the pancreas, the immune system and the brain itself, which is why researchers have catalogued hundreds of separate actions for a hormone most people associate only with breastfeeding.

What makes prolactin unusual is how it is controlled. Most pituitary hormones are switched on by a signal from the hypothalamus above. Prolactin works the other way round: the hypothalamus continuously releases dopamine, and dopamine tells the pituitary to hold back. Prolactin is kept in check by a brake rather than driven by an accelerator, which explains a great deal about why levels rise. Anything that interferes with dopamine, whether a medication, a growth pressing on the pituitary stalk, or the ordinary physiology of pregnancy, lifts the brake and prolactin climbs.

Where is prolactin produced?

The overwhelming majority comes from lactotroph cells in the anterior pituitary gland. Smaller amounts are made locally in the lining of the womb, in breast tissue and in some immune cells, where the hormone acts on nearby tissue rather than travelling through the bloodstream. A blood test is picking up the pituitary contribution almost entirely.

What does prolactin do?

The clearest job is preparing breast tissue during pregnancy and then triggering and sustaining milk production after birth. Levels climb steadily across the nine months, but milk does not flow until the placenta is delivered and the high progesterone that had been blocking the effect falls away. After that, every feed sends a signal from the nipple to the brain that releases another pulse of prolactin, which is why supply responds to demand.

Beyond that, prolactin’s main function is regulatory. It shapes how the pituitary releases Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH), the two signals that tell the ovaries to ovulate and the testes to make testosterone and sperm. At normal levels that influence is subtle and useful. When prolactin climbs well above normal it suppresses those signals, and that single mechanism sits behind almost every symptom of a high result: raised prolactin turns down the volume on the rest of your reproductive hormones.

Men produce prolactin from the same pituitary cells as women, at lower levels in every age band, which is why the reference ranges are set separately. Because it acts on testosterone rather than replacing it, its effects in men are felt at one remove, and the two hormones are far more informative read together than either is alone. Men also have no equivalent of pregnancy or breastfeeding, so nothing in male physiology is supposed to push prolactin high, and a result that is genuinely and persistently raised has a shorter list of possible explanations than the same result in a woman. That is why prolactin belongs alongside Testosterone (total) in any panel looking at male hormone health rather than in place of it.

Prolactin also plays a part in the immune response, in how the body handles insulin and stores fat, and in behaviour, with research linking it to bonding and to the sense of satisfaction that follows sex.

The role of prolactin in women

Prolactin is unusual among reproductive hormones in that what counts as normal depends less on your age than on your circumstances. A reading of 3,000 mIU/L is exactly right in a woman who gave birth last month and a reason to investigate in a woman who did not. Pregnancy and breastfeeding are therefore the first two questions worth answering before looking at a female result at all, because they change the interpretation completely rather than shifting it slightly.

The other thing worth knowing is how easily raised prolactin is missed in women. Because its effects reach you through falling oestrogen rather than directly, what you notice tends to look like a dozen other explanations, and the life stages when prolactin problems are most likely to appear are also the ones when women are most often told they are simply tired, stressed or approaching menopause. A blood test can separate a hormone problem from a life problem, and reading prolactin next to Oestradiol (Oestrogen) and Luteinising Hormone (LH) shows not just whether the level is raised but whether it is actually doing anything.

How prolactin affects fertility

Prolactin affects fertility indirectly but powerfully. Raised levels suppress the pulses of gonadotropin-releasing hormone from the hypothalamus, which in turn dampens LH and FSH. In women that means ovulation becomes irregular or stops, and without ovulation there is no egg to fertilise. Even where periods continue, the luteal phase can shorten, which makes implantation less likely. In men, the same suppression lowers testosterone and reduces sperm production and quality.

The encouraging part is that this is one of the more reversible causes of difficulty conceiving. Once the underlying reason is identified and the level comes down, ovulation usually returns and fertility with it. Prolactin is a standard part of a fertility workup for exactly this reason, and it is most informative read next to Luteinising Hormone (LH), Follicle Stimulating Hormone (FSH) and Anti-Müllerian Hormone.

What are normal prolactin levels?

A normal prolactin result depends on your sex, on the range your laboratory uses, and on when the sample was taken. The Forth reference range is 102 to 496 mIU/L for women who are not pregnant or breastfeeding and 86 to 324 mIU/L for men. Most people sit comfortably inside those boundaries, and the typical result is nowhere near the top of them: across our customer data the median is 340 mIU/L in women and 283 mIU/L in men.

Prolactin reference ranges in both mIU/L and ng/mL, showing why the same result can look like a very different number depending on the unit used.

How prolactin is measured: mIU/L vs ng/mL

This causes more confusion than any other part of a prolactin result. UK laboratories, including ours, report in milli-international units per litre, written mIU/L or sometimes mU/L, which mean exactly the same thing. Most American sources, and a good proportion of what surfaces in an online search, report in nanograms per millilitre, ng/mL. The numbers look wildly different because the units are different, not because anything is wrong.

To convert, multiply ng/mL by about 21 to get mIU/L, or divide mIU/L by about 21 to go the other way. A result of 20 ng/mL is therefore roughly 420 mIU/L, and 500 mIU/L is roughly 24 ng/mL. If you have read somewhere that a prolactin of 40 is high, that figure almost certainly refers to ng/mL, which works out at around 850 mIU/L and is indeed well above range. Check which unit your report uses before comparing your number to anything you have read elsewhere.

Normal prolactin levels in women

For women who are not pregnant or breastfeeding, a result between 102 and 496 mIU/L falls within the Forth range, roughly 5 to 23 ng/mL. In our data, 72% of female results sit inside the range, 27% come back above it and fewer than 2% fall below. 

That 27% deserves a caveat rather than alarm, for two reasons. Our records do not capture whether a woman was pregnant or breastfeeding at the time of testing, so that group is included in the female figures and pushes the proportion upwards. Prolactin is also one of the most reactive hormones in the body, so an anxious blood draw, a broken night or a recent feed can lift a result on its own. 

Prolactin levels during the menstrual cycle

Prolactin does move across the cycle, though far less dramatically than oestrogen or progesterone. In Forth data from women with regular periods who are not using hormonal contraception, the median dips to its lowest around days 11 to 14, at 332 mIU/L, and rises to its highest in the luteal phase, reaching 403 mIU/L between days 22 and 28. That is a swing of roughly 20% between the quietest and busiest points of the month.

For most people that variation sits comfortably inside the normal range and changes nothing about how a result is read. It becomes relevant when a result lands close to the upper limit late in the cycle, since the same person tested a fortnight earlier might have come in comfortably normal. If you are testing prolactin alongside Oestradiol (Oestrogen), Progesterone or FSH, the day of testing will already be set by those hormones, and prolactin is fine to measure at the same time.

Chart showing median prolactin across the menstrual cycle in women with regular periods who are not using hormonal contraception, from days 1 to 5 through to days 22 to 28.

Prolactin levels during pregnancy and breastfeeding

Pregnancy transforms prolactin completely. Levels begin rising in the first trimester under the influence of rising oestrogen, climb throughout, and by the third trimester can be ten to twenty times higher than before conception, reaching several thousand mIU/L. This is the pituitary preparing the breast for milk production, and the gland itself enlarges during pregnancy to manage the workload.

After birth, prolactin falls sharply within the first few weeks in women who do not breastfeed, returning to typical levels within about three months. In women who do breastfeed, baseline levels stay elevated and each feed produces a further surge, with the pattern gradually settling as feeds become less frequent. Sustained high prolactin during this period is exactly what should be happening, and it is also why a prolactin test is rarely useful while breastfeeding: the number will be high, and correctly so.

The typical prolactin pattern through pregnancy and breastfeeding, where levels many times above the normal range are exactly what should be happening.

Prolactin levels in non-pregnant women

If you are not pregnant and not breastfeeding, interpretation is more straightforward, because none of the physiological reasons for a large rise apply. A result above the range in a woman who is not pregnant is worth investigating, particularly if periods have changed, if there is milky nipple discharge, or if you have been trying to conceive without success. It rarely means something serious, but it does mean the number deserves a second look rather than a shrug.

Looking at where results actually fall, around 13% of female results are just above the top of the range and a further 14% are well above it. That split matters, because the two groups usually have very different explanations. A reading fractionally over the line often reflects the circumstances of the test. A reading two or three times the upper limit is telling you something about your physiology.

Chart showing the share of prolactin results falling below range, in the lower and upper half of the normal range, above range and well above range, for women and for men.

Normal prolactin levels in men

The male reference range is 86 to 324 mIU/L, approximately 4 to 15 ng/mL. Just over half of male results in our data sit inside that range, with 41% above it and 2% below. That proportion above range looks alarming and mostly is not, for reasons worth spelling out:

• The male range leaves very little headroom: the typical male result in our data is 283 mIU/L, only 41 points below the upper limit of 324, whereas the typical female result of 340 has more than 150 points to spare before 496. 
• Prolactin is also one of the most reactive hormones in the body, rising with stress, broken sleep and the timing of the blood draw, so it takes very little to nudge an ordinary male reading over a line that was already close. 
• And men who choose to measure prolactin are not a random sample of men; many are testing because something already felt off, which lifts the proportion of high results in any dataset like ours.

None of that makes a high result meaningless. It does mean the flag on its own tells you far less than how far above the line you are, and whether it holds on a second test. Around 19% of male results are only just above the top of the range and 22% are well above it, and those two groups usually have different explanations. A man at 350 mIU/L with no symptoms and a stressful morning behind him is in a genuinely different position from a man at 1,500 mIU/L and a year of low libido.

Normal prolactin levels by age

Prolactin declines gradually with age in both sexes, and the pattern is clear across our data. In women the median rises through the twenties, peaks at 394 mIU/L between 26 and 30, then falls steadily to 266 mIU/L from 46 onwards. In men the decline is smoother, from 338 mIU/L in the early twenties to 245 mIU/L at 46 and over. Women sit higher than men in every single age band, which is why the reference ranges are separate.

The drop with age tracks the wider decline in reproductive hormone activity, and in women the fall after 45 overlaps with the menopause transition. It is a good reason not to compare your result with a friend of a different age and assume something is wrong. What counts as typical shifts across a lifetime, and your own trend over time tells you more than any single number.

Median prolactin by age group, with women higher than men at every age and both drifting downwards from the late twenties onwards.

When are prolactin levels highest and lowest?

Prolactin follows a strong daily rhythm tied to sleep rather than to the clock. Levels begin climbing about an hour after you fall asleep and reach their peak in the early hours of the morning, then fall away as the morning goes on. The lowest point of the day is mid-morning, roughly between 9am and 11am, which is precisely why that window is the standard time to take a prolactin sample.

Our own results show how much this matters in practice. Among women who collected their sample before 7am, 58% came back above the reference range; among those who collected between 10am and 11am, that fell to 13%. In men the same pattern runs from 75% down to 22%. Nothing about those people changed, only the hour on the clock. The single biggest thing you can do for an accurate prolactin result is to collect it mid-morning, and it explains why results drift upwards again from late afternoon as the overnight rise begins to build.

Chart showing the share of prolactin results above the reference range according to the time the sample was collected, for women and for men.

High and low prolactin levels

Most people look up prolactin because a result came back outside the range. The reassuring part is that the reasons are usually identifiable, and often reversible.

What is considered high prolactin?

Hyperprolactinaemia is the medical term for prolactin above the normal range: above 496 mIU/L in women or 324 mIU/L in men on the Forth range, roughly 23 ng/mL and 15 ng/mL respectively. Ranges vary between laboratories, so the range printed on your own report is the one that applies to you.

How far above matters far more than the fact of being above, and UK laboratory guidance sets out roughly where the meaningful lines fall:

• A result sitting just over the limit is frequently explained by the circumstances of the test and often settles on a properly timed repeat. 
• Once a result passes about 700 mIU/L it is generally treated as clinically significant rather than incidental, and most UK laboratories will automatically screen that sample for macroprolactin before anything else happens. 
• A level that stays above 1,000 mIU/L on a repeat test is usually the point at which referral to an endocrinologist is considered, particularly where there are symptoms or no obvious cause. 
• Results in the region of 2,000 to 5,000 mIU/L prompt both a confirmatory repeat and referral, and above 5,000 mIU/L that referral becomes urgent, with a prolactinoma the leading explanation.

That macroprolactin check is worth understanding, because it saves a good deal of unnecessary worry. Some people carry a form of prolactin bound to an antibody, which shows up on the test but is biologically inactive and causes no symptoms. If your result is high and nothing about your health matches it, this may be all it is, and screening for it on a first raised sample is routine rather than something you need to request.

What causes high prolactin?

Prolactin rises for reasons ranging from entirely ordinary to genuinely medical, and the everyday explanations are far more common. Physical and emotional stress raise it, as do poor sleep, intense exercise, sex, nipple stimulation and even the anxiety of having blood taken. A single mildly raised result is more likely to reflect the hour before your test than anything happening inside your pituitary gland, which is why repeating the test properly is almost always the first step rather than the last.

Prolactinomas and raised prolactin levels

A prolactinoma is a benign growth on the pituitary gland made up of prolactin-producing cells. It is the most common type of pituitary tumour and it is not cancer, a distinction worth stating plainly because the word tumour does a lot of frightening work. Prolactinomas do not spread, and they are usually managed successfully with medication rather than surgery.

Smaller ones, under 10mm, cause symptoms through the hormone alone. Larger ones can press on surrounding structures and add headaches or changes to peripheral vision. What causes them is not fully understood, and the great majority arise with no family history and no identifiable trigger. How high prolactin runs broadly tracks the size of the growth: a large prolactinoma can drive levels into the tens of thousands of mIU/L, while a small one may lift prolactin only into the low thousands, or less. A modest result does not rule a prolactinoma out, which is why a level that stays above 1,000 mIU/L with no other explanation gets investigated rather than watched. An MRI scan is how one is confirmed.

Medicines that increase prolactin

Medication is the most common non-physiological cause of raised prolactin, and it is the first thing a clinician should ask about. Because dopamine is the brake, any drug that blocks dopamine will lift prolactin as a side effect. The main groups are:

• antipsychotics, particularly risperidone, haloperidol and sulpiride; 
• anti-sickness medicines such as metoclopramide and domperidone; 
• some antidepressants, especially SSRIs and tricyclics; 
• certain blood pressure medicines including methyldopa and verapamil; 
• opioid painkillers; 
• and proton pump inhibitors such as omeprazole. 

Oestrogen-containing medicines can nudge levels upward too, though in our own data the effect of hormonal contraception is negligible: the median for women using contraception is 357 mIU/L against 360 mIU/L for those not using it, a difference of no practical significance.

If a medicine is the cause, that is useful information rather than a problem to solve alone. Never stop a prescribed medication because of a blood result. Take the result to whoever prescribed it and have the conversation together.

Median prolactin by contraception use and method, showing a gap of a few points between users and non-users, which is no difference in practice.

Health conditions that cause high prolactin levels

Several health conditions can raise prolactin levels, either by stimulating its release or by slowing its removal from the bloodstream:

• Underactive thyroid (hypothyroidism): when thyroid hormone levels fall, the brain increases Thyrotropin-Releasing Hormone (TRH), which can stimulate prolactin as well as TSH. Treating the thyroid problem will often bring prolactin levels back down, which is why it can be useful to check Thyroid Stimulating Hormone (TSH) at the same time.
• Chronic kidney disease: reduced kidney function can slow the clearance of prolactin from the blood, causing levels to rise.
• Liver disease: the liver also helps process and clear hormones, so significant liver dysfunction can contribute to elevated prolactin levels.
• Polyendocrine Metabolic Ovarian Syndrome (PMOS): some people with PMOS have mildly raised prolactin, although the association is inconsistent. In practice, prolactin is often tested during a PMOS investigation to rule out another cause of symptoms such as irregular periods or problems with ovulation.
• Chest wall injury or irritation: Surgery, trauma or shingles affecting the chest can stimulate prolactin release through nerve pathways similar to those activated during breastfeeding.

Causes of high prolactin in men

The causes in men are broadly the same, but the pattern differs. Medication and stress account for most mildly raised readings, and prolactinomas, when they occur in men, tend to be found later and to be larger, because the early symptoms are vague and easily attributed to age or overwork.

The combination to watch for is raised prolactin alongside low testosterone. If both are out of range and libido, erections or energy have changed, that is a pattern worth taking to a GP rather than monitoring indefinitely. Given how often a mildly raised male result reflects the test rather than the man, a repeat under proper conditions is the sensible first move.

Symptoms of high prolactin

Symptoms depend on how high the level is and how long it has been there. In women, the earliest and most common signs involve the menstrual cycle: periods that become irregular, much lighter, or stop altogether. Some women notice a milky discharge from one or both nipples, which can be startling but is a direct and explicable consequence of the hormone doing its job at the wrong time. Difficulty conceiving is often what brings the whole thing to light. Lower oestrogen can also bring vaginal dryness, reduced libido and, over longer periods, a gradual loss of bone density.

In men the picture is quieter: reduced sex drive, difficulty with erections, low energy, loss of muscle bulk and occasionally breast tenderness or enlargement. Because these develop slowly and overlap with so much else, men typically live with them for longer before investigating.

How high prolactin is treated

Treatment follows the cause rather than the number. If a medication is responsible, the conversation is about whether an alternative is suitable. If an underactive thyroid is behind it, treating the thyroid brings prolactin down with it. If the level is only mildly raised and there are no symptoms, the usual approach is to repeat the test under good conditions and watch rather than intervene.

Where a prolactinoma is confirmed, first-line treatment is a dopamine agonist, usually cabergoline or bromocriptine. These restore the brake the growth has overridden, and they work in the large majority of cases, lowering prolactin, shrinking the growth and restoring periods and fertility. Surgery is reserved for the minority who cannot tolerate the medication or do not respond to it.

How long does it take for prolactin levels to fall?

Prolactin itself clears from the blood quickly, with a half-life measured in tens of minutes, so a rise caused by stress, sex or a poor night’s sleep will have resolved by the following morning. This is why a repeat test done properly so often comes back normal.

Where a cause is being treated, the timescale stretches. Stopping or switching a responsible medication usually brings levels down within a few days to a few weeks. Treating an underactive thyroid takes longer, generally a few months, because the thyroid hormones themselves need time to stabilise. With cabergoline for a prolactinoma, levels typically fall substantially within two to four weeks and normalise across two to three months, with shrinkage of the growth following behind. A repeat test six to eight weeks after any change is usually the right interval to see whether it is working.

How to lower your prolactin levels naturally

If your prolactin is high because of a prolactinoma, a medication or a thyroid condition, no dietary or lifestyle change will fix it, and supplements marketed for the purpose have very little evidence behind them.

What lifestyle genuinely influences is the everyday variation. Prolactin responds to stress, so anything that reliably lowers your stress load will reduce the spikes. Consistent, sufficient sleep helps, because a disrupted sleep pattern disrupts the rhythm that governs prolactin release. Very intense exercise causes a temporary rise, so easing back before a test is sensible even if hard training is otherwise good for you. Avoiding nipple stimulation and sex on the day before a test removes another avoidable trigger.

There is one piece of genuinely useful context in our own data. Prolactin shows almost no relationship with body weight: median levels are essentially flat across BMI bands in both sexes, at 357, 338 and 332 mIU/L across the normal, overweight and obese bands in women. Losing or gaining weight is not a lever for prolactin, which is worth knowing before anyone spends effort in that direction for this particular reason.

Chart showing median prolactin for women and men across four BMI bands, staying effectively flat in both sexes, so weight is not a lever for changing it.

What is considered low prolactin?

Low prolactin, sometimes called hypoprolactinaemia, means a result below the bottom of the reference range: under 102 mIU/L in women or 86 mIU/L in men on the Forth range. It is genuinely uncommon. Only 1.5% of female results and 2.4% of male results in our data fall below range, and unlike a high result, a low one is rarely investigated on its own.

What causes low prolactin?

The most common cause is medication that increases dopamine, which strengthens the brake. That includes the dopamine agonists used to treat prolactinomas and Parkinson’s disease, where a low level is a predictable consequence rather than a problem when the dose is right.

Beyond that, low prolactin can point to underactivity of the pituitary gland itself, known as hypopituitarism, which may follow damage from surgery, radiotherapy, a head injury or, rarely, severe blood loss around childbirth. In these situations prolactin is almost never low in isolation. Other pituitary hormones fall too, which is what makes the pattern recognisable and why a low prolactin result is read alongside LH, FSH, TSH and Cortisol (9am) rather than by itself.

Symptoms of low prolactin

Because it is so rare, the symptom picture is less well defined. In women who have recently given birth, the clearest sign is difficulty producing enough breast milk. Outside that setting, most of what is reported comes from studies in men, where low prolactin has been associated with reduced sexual satisfaction, erectile difficulties and, in some research, low mood and metabolic changes. The evidence base is thinner than for high prolactin and the findings are not consistent.

If low prolactin appears alongside other low pituitary hormones, the symptoms you notice are usually driven by those rather than by prolactin itself: fatigue, low libido, cold intolerance and unintended weight change, depending on which hormones are affected.

How to increase your prolactin levels naturally

If you are breastfeeding and want to support supply, the mechanism to work with is the feedback loop itself. Frequent feeding or expressing, skin-to-skin contact and fully draining the breast all send the signal that triggers prolactin release, and this is far more effective than anything you can eat. Adequate sleep and lower stress support the same loop, though both are easier to prescribe than to arrange with a newborn.

Foods and herbs marketed as galactagogues, including oats, fennel, fenugreek and brewer’s yeast, are widely used and generally harmless, but the evidence that they raise prolactin meaningfully is weak. A lactation consultant or infant feeding adviser will be more useful than a supplement.

What does a prolactin test measure?

A prolactin blood test, sometimes labelled serum prolactin or PRL, measures the total concentration of prolactin in a blood sample, reported in mIU/L in the UK. That single number tells you whether your pituitary is releasing prolactin within the expected range for your sex. It is a standard, well-established test used in fertility investigations, in working up irregular periods or nipple discharge, and in men with low libido or erectile difficulties.

What it does not do on its own is explain why. A raised result identifies that something is lifting the brake, but distinguishing between stress, a medication, an underactive thyroid and a prolactinoma requires context: your symptoms, your medications, a repeat test and usually a few other hormones alongside. A prolactin result is the beginning of a question, not the answer to one, which is exactly why it is most useful inside a broader hormone panel.

Why take a prolactin blood test?

The most common reasons are:

• periods that have become irregular or stopped without an obvious explanation;
• difficulty conceiving after several months of trying;
• milky discharge from the nipples outside pregnancy or breastfeeding;
• and reduced libido or erectile difficulties in men. 

It is also worth checking if you take a medication known to raise prolactin and have developed any of these symptoms, or if you are experiencing persistent headaches together with hormonal changes.

How is a prolactin test done?

Prolactin is measured from a small blood sample. In a clinical setting that usually means a venous draw from the arm; with Forth it can also be collected from a finger-prick sample at home, which is what most of our customers use. 

You do not need to fast, and no special preparation is required beyond timing the sample sensibly and avoiding the handful of triggers described below.

Can you check your prolactin at home?

Yes. A home finger-prick kit collects a small blood sample that you post to the laboratory, and prolactin is measured on the same analysers and against the same reference ranges as a clinic sample. The practical advantage is control. You can collect at the right time of day, in your own home, without the rush of getting to an appointment, and the calmer the collection the more representative the result. Given how sensitive prolactin is to stress, that is a real benefit rather than a convenience.

How to prepare for your test

Timing does most of the work. Aim to give your sample between 9am and 11am, and ideally at least an hour after waking, so you are sampling at the natural low point of the day rather than the tail of the overnight rise. Our own results show what that is worth: among women sampling before 7am, 58% came back above range, against 13% of those sampling between 10am and 11am.

In the twenty-four hours before, avoid sex and nipple stimulation, since both trigger prolactin release directly, and skip any unusually intense training session. On the morning itself, give yourself a few unhurried minutes before collecting rather than rushing in from a stressful commute. The most common reason for a falsely high prolactin result is the hour before the test, not the test itself. Keep taking any prescribed medication as normal, and note down what you take so it can be considered when your result is interpreted.

When in your cycle should you test?

Prolactin can be measured on any day of the cycle. If you are testing prolactin on its own, choose whichever day suits you and make a note of it.

In practice, most women test prolactin as part of a wider panel, and the other hormones set the day. FSH, LH and oestradiol are usually measured on days two to five of the cycle, counting day one as the first day of full flow, while progesterone is measured around seven days before your next period is due. Both are perfectly acceptable for prolactin. If you are retesting a borderline result, matching the same phase of the cycle as the first test removes one variable, and so does using the same time of day.

How to read your prolactin results

Start with the units and the range printed on your own report, then read your number against them. A result inside the range means your pituitary is releasing prolactin as expected. A result below range is uncommon and usually only significant when other pituitary hormones are low too.

If your result is above range, the next question is how far above. A reading a little over the limit, particularly in a man, is very often explained by the circumstances of the test, and a properly timed repeat in a few weeks is the sensible response. A reading well above the limit, or one accompanied by absent periods, nipple discharge, difficulty conceiving or persistent low libido, should be taken to a GP, who can review your medications, check thyroid function and arrange imaging if that is warranted.

A single result is a snapshot of a hormone that moves through the day and the month. What tells the real story is your trend across repeated tests, read against your symptoms and alongside the rest of your hormone picture.

What biomarkers should I test with prolactin?

Prolactin makes far more sense inside a panel than on its own, because almost everything it does happens through other hormones.

• Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH) show whether raised prolactin is actually suppressing the signals to the ovaries or testes, which is the difference between an abnormal number and a problem you can feel.
• Oestradiol (Oestrogen) and Progesterone show the downstream effect on the cycle, and Testosterone (total) does the same in men, where low testosterone alongside high prolactin is the pattern most worth acting on. 
• Sex Hormone Binding Globulin (SHBG) and the Free Androgen Index refine that picture by showing how much testosterone is actually available to your body.
• Thyroid Stimulating Hormone (TSH) belongs in any prolactin investigation, since an underactive thyroid is one of the most common and most treatable causes of a raised result. 
• Anti-Müllerian Hormone adds information about ovarian reserve that prolactin cannot provide, for women asking fertility questions, 
• Ferritin and Vitamin D (25 OH) are worth including where fatigue is part of the picture, because tiredness has more causes than any single hormone.

Prolactin tests from Forth

Prolactin is included in our hormone panels, where it is measured alongside the reproductive and thyroid markers that give it context:

• The Female Hormone Imbalance Test is the most direct starting point for women with irregular periods, unexplained symptoms or fertility questions, combining prolactin with FSH, LH, oestradiol, testosterone and thyroid markers so that a raised result can be interpreted properly rather than in isolation.
• The Male Hormones Blood Test measures prolactin alongside total testosterone, SHBG, the free androgen index, LH and FSH, which is the combination that turns a prolactin number into something men can actually act on.

Every sample is analysed in a UKAS-accredited laboratory working to NHS standards, and every result is reviewed by a doctor and returned with a personalised explanation of what your numbers mean. Because your results are stored over time, a second test six months later is not another isolated snapshot but a trend line, and trends are where the real intelligence lives.

FAQs about Prolactin