What Is Testosterone And Which Blood Tests Check Testosterone Levels?

What Is Testosterone?

Testosterone is an androgen, the male hormone produced predominantly in the testes, which is responsible for many of the male sex characteristics. Women also produce small amounts of testosterone in the ovaries and adrenal glands.

Free testosterone refers to the amount of the hormone which is not bound to either albumin or sex hormone binding globulin. [1]

Which tests include this marker?

Why Take A Testosterone Blood Test?

Testosterone levels can be indicative of various conditions in both males and females. Testosterone levels in men naturally fall as they age, leading to symptoms such as reduced sex drive and erectile dysfunction. Abnormal levels in women can cause conditions like polycystic ovary syndrome (PCOS).

A testosterone test is usually used if you suspect your levels may be too high or too low. As a result, you may display some unpleasant and uncomfortable symptoms.

You can test your testosterone levels along with other key fertility hormones by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include testosterone such Female FertilityMale HormonesMenopause Health and our Vitality package which includes analysis of over 30 key biomarkers for good health.

What Function Does Testosterone Have In The Body?

Testosterone has important roles in the human body affecting several organs as well as our sexual development and function.

In men, the secretion of testosterone follows the circadian rhythm, so their levels are highest in the early hours of the morning. In early adulthood, testosterone is required for the growth and regulation of the prostate gland. Prostatic cell growth occurs because testosterone travels via the blood to the prostate gland where it is converted to dihydrotestosterone. [2]

Testosterone is responsible for the development of the male reproductive organs and system. The hormone is also essential for the development of sperm in adulthood. As boys mature during puberty, testosterone is associated with:

  • Increases in height
  • Growth of body and pubic hair
  • Enlargement of the penis, teste and prostate gland
  • Changes in sexual behaviour and aggression

Testosterone also regulates the secretion of other hormones like luteinising hormone and follicle stimulating hormone.

In women, the production of testosterone in the ovaries and adrenal glands is usually converted to oestradiol, a type of oestrogen.[3]

The levels between men and women differ greatly. Men, on average, have 10 times more testosterone than women.

How Do Changes In Testosterone Affect Health And Wellbeing?

Increases in testosterone in women and decreases in men can negatively affect our health and wellbeing,

Naturally, as men age, their testosterone levels fall which can cause various symptoms and effects. The normal levels of testosterone in men are:

  • 2% free testosterone
  • 38% bound to albumin
  • 60% bound to SHBG[4]

In females, increased levels of free testosterone can cause polycystic ovary syndrome (PCOS). PCOS causes the loss of periods as well as some unpleasant symptoms.

If you are worried about your testosterone level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.

What Can Cause Testosterone To Change?

Polycystic ovary syndrome affects the function of the ovaries and causes unwanted side effects. Tumours in the adrenal gland or ovary are also responsible for increases in female testosterone levels.

A decreased circulating testosterone and SHBG level are risk factors for metabolic syndrome in elderly men.[5] Metabolic syndrome is the name given to a combination of diabetes, high blood pressure and obesity. Metabolic syndrome increases the risk of coronary heart disease, stroke and cardiovascular disease.

A male’s testosterone level may fall because of damage to the testes, alcoholism or viruses like mumps.

What Are The Most Common Symptoms?

Symptoms of PCOS include:

  • Irregular or the absence of periods
  • Excess hair growth (known as hirsutism) usually affects the face, chest, back or buttocks
  • Acne
  • Weight gain
  • Hair loss
  • Difficulty getting pregnant
  • Increased risk of high cholesterol and type 2 diabetes[6]

PCOS affects 1 in 5 women who are of reproductive age and can have some psychological side effects, like:

  • Reduced quality of life
  • Low self-esteem
  • Depression
  • Anxiety

The symptoms of metabolic syndrome are:

  • A waist circumference above 94cm in European men or 90cm in South Asian men
  • A waist circumference above 80cm in women
  • High blood pressure
  • High triglyceride levels
  • Insulin resistance
  • Increased risk of blood clot development
  • Inflammation

Metabolic syndrome is diagnosed if you have at least 3 of these symptoms.[7]

Testosterone levels gradually fall as men age, usually at a rate of approximately 2% each year from the age of 30 or 40. As a result, there may be symptoms such as:

  • Changes in mood and irritability
  • Reduced muscle mass and reduced ability to exercise
  • Lack of enthusiasm or energy
  • Difficulty sleeping
  • Increased feeling of tiredness
  • Poor concentration
  • Redistribution of fat resulting in the development of man boobs or a large belly[8]

How To Keep Testosterone In The Healthy Range

Because testosterone has major roles in the growth and maintenance of muscle and bone, it is an important hormone with regards to exercise and physical training. Studies have shown higher intensity exercise cause higher levels of testosterone in the body. [9]

Diet and lifestyle choices can help to treat and control both PCOS and metabolic syndrome. Heart disease and diabetes are side effects of PCOS, as well as major factors in SHBG and so eating the right diet is key to preventing them. Eating a diet with low glycaemic index foods can be beneficial. Low GI foods raise blood sugar slowly which reduces the symptoms of PCOS and they help to manage diabetes.

Low glycaemic foods include:

  • Oatmeal
  • Oat Bran
  • Muesli
  • Pasta
  • Barley
  • Bulgar wheat
  • Sweet potato
  • Butter beans
  • Peas
  • Legumes
  • Lentils
  • Fruit
  • Carrots
  • Non-starchy foods

Low GI foods are particularly useful in conditions which make individuals resistant to insulin. [10]

Being overweight is a risk factor for both metabolic disease and PCOS and increases the severity of these conditions. Physical activity is beneficial for weight loss but also improves the body’s response to insulin.

As men increase in age their levels of testosterone levels reduce. Men in their 70s have approximately 40% less testosterone than men in 20s. The reduced testosterone level is associated with a lower quality of life as well as reduced muscle mass and an increased risk of osteoporosis. In middle-aged men, who take part in moderate to vigorous exercise, greater improvements in testosterone levels also improve cardiopulmonary fitness. [11] Supplementing your diet with calcium and vitamin D is a good way to maintain strong bones and teeth, although you should be able to get your reference nutrient intake by eating a healthy balanced diet.[12]

Tests that include this marker


Low testosterone can affect libido, mood and muscle mass. Check your level with a simple at-home finger prick test.


Male Hormones

A comprehensive test of key male hormones which can affect libido, muscle strength, energy and much more.


Female Fertility

This profile analyses key hormones which can not only affect your fertility, but also mood, energy and weight.


Menopause Health

For women in various stages of the menopause who want to check hormone levels as well as the impact changes may be having on their overall wellbeing.


Body Fit

For those who enjoy keeping fit and want to optimise performance and check the impact their training is having on their health.



With over 45 biomarkers, this health check empowers you to gain a deep understanding about your inside health.



Our most advanced health check which analyses over 50 biomarkers. For those who want a deep understanding of their health.



[1] Lab Tests Online UK. (2016). Testosterone Test. Available at: https://labtestsonline.org.uk/tests/testosterone-test

[2] Alvarado, L, C. (2011). Total Testosterone in Young Men is More Closely Associated than Free Testosterone with Prostate Cancer Disparities. Ther Adv Urol: 3(3), pp 99-106.

[3] You and Your Hormones. (2018). Testosterone. Available at: https://www.yourhormones.info/hormones/testosterone/

[4] Tyagi, V., Scordo, M., Yoon, R, S., Liporace, F, A and Wissner Greene, L. (2017). Revisiting the Role of Testosterone: Are We Missing Something? Rev Urol: 19(1), pp 16-24.

[5] Chubb, S, A, P et al. (2008). Lower Sex Hormone-Binding Globulin is More Strongly Associated with Metabolic Syndrome than Lower Total Testosterone in Older Men: The Health in Men Study. European Journal of Endocrinology: 158(6).

[6] Ehrmann, D, A. (2005). Polycystic Ovary Syndrome. The New England Journal of Medicine: 352, pp 1223-36.

[7] NHS. (2016). Metabolic Syndrome. Available at: https://www.nhs.uk/conditions/metabolic-syndrome/

[8] NHS. (2019). The ‘Male Menopause’. Available at: https://www.nhs.uk/conditions/male-menopause/

[9] Lane, A, R and Hackney, A, C. (2014). Relationship Between Salivary and Serum Testosterone Levels in Response to Different Exercise Intensities. Hormones.

[10] The Association of UK Dietitians. (2016). Polycystic Ovary Syndrome (PCOS). Available at: https://www.bda.uk.com/foodfacts/pcos.pdf

[11] Hawkin, V, H., Foster-Schubert, K and Chubak, J et al. (2008). Effect of Exercise of Serum Sex Hormones in Men: A 12 Month Randomized Clinical Trial. Med Sci Sports Exerc: 40(2), pp 223-233.

[12] NHS. (2019). Prevention Osteoporosis. Available at: https://www.nhs.uk/conditions/osteoporosis/prevention/

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