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Folate (serum)

Folate, also known as vitamin B9, is an essential nutrient acquired from the diet that has important roles in the formation of red blood cells and DNA synthesis. Low levels can indicate deficiency and may cause anaemia.

Author: Leanne Edermaniger

April 30, 2024

Reviewed by: Dr Thom Phillips

In this article:

What is Folate (Serum)?

Folate is the natural form of vitamin B9, a water-soluble vitamin that is important for the development of DNA, protein metabolism, and many other bodily functions. Folate naturally occurs in some foods and is also widely available in supplement form.

B vitamins are essential for the maintenance of good health and wellbeing. They influence energy levels, metabolism, and brain function. Vitamin B9 specifically:

  • Supports the formation of red blood cells alongside vitamin B12[1].
  • Aids DNA synthesis and repair. All cells in the body need folate for cell division and growth. Without adequate folate levels, DNA can become unstable and mutations may occur[2].
  • Regulates homocysteine levels by helping your body to use this amino acid. Folate deficiency can increase homocysteine levels, a risk factor for cardiovascular disease[3].
  • Prevents neural tube defects in babies, such as spina bifida and anencephaly due to its role in nucleotide synthesis[4].

What is a Good Folate Level?

The healthy range for folate levels depends on several factors. For example, the reference ranges can be different depending on the laboratory and the techniques they use to determine folate levels.

According to the National Institute for Health and Care Excellence (NICE), folate reference ranges are as follows:

Folate deficiency indicated < 3 micrograms/L (µg/L) < 7 nanomoles/L (nmol/L)
Suggestive folate deficiency 3 – 4.5 µg/L 7 – 10 nmol/L[5]
Normal range > 4 µg/L > 9 nmol/L
Elevated folate levels > 20 µg/L > 45.3 nmol/L[6]

At Forth, our data shows that 57% of men and 43% of women have healthy folate levels.

How Do Folate and Vitamin B12 Work Together?

Vitamin B9, folate, and vitamin B12 work closely together to help make red blood cells, synthesise DNA to build healthy cells, and support immune function.

Here’s a short breakdown of how vitamin B9 and B12 interact:

  1. DNA synthesis: Folate and B12 are crucial for the synthesis of DNA and RNA, critical for the growth and division of cells in the body.
  2. Red blood cell formation: The production and maturation of red blood cells are reliant on these two B vitamins. Deficiency in either can result in abnormally large red blood cells which do not effectively carry oxygen (megaloblastic anaemia).
  3. Homocysteine metabolism: Both B12 and B6 are essential for homocysteine metabolism, an amino acid that, at high levels, could increase the risk of cardiovascular disease, and is a by-product of protein breakdown.
  4. Nervous system function: Vitamin B12 is important for the maintenance of the protective coating around nerve cells called the myelin sheath, and for proper neurological function. Vitamin B6, on the other hand, is important for neural cell division and tissue repair.

If you are deficient in either of these vitamins, then it can cause anaemia, so it is important to check your folate and vitamin B12 levels to find out the cause of any symptoms you may be experiencing.

What Causes Low Folate?

Folate is a water-soluble vitamin which means the human body is unable to store it, so it must be acquired through our diet to keep our cells functioning normally. Generally, if you take in too much of a water-soluble vitamin, the excess will be excreted out through your urine.

Too little, however, can lead to folate deficiency.

What causes folate deficiency?

  • Several factors can cause folate deficiency:
  • Inadequate dietary intake
  • High alcohol intake
  • Digestive conditions such as coeliac disease, short bowel syndrome and gastric bypass
  • Medicines including phenytoin, methotrexate, sulfasalazine and trimethoprim
  • Genetics[7]

Symptoms of folate deficiency

  • Headaches
  • Loss of appetite
  • Vision problems
    Rapid breathing or shortness of breath
  • Weakness
  • Tiredness
  • Sore, red tongue
  • Memory issues

Can cancer cause low folate?

There is some research which suggests that cancer patients are at an increased risk of developing folate deficiency. A cohort study published in 2018 found that 6.8% of hospitalised cancer patients were folate deficient[8].

There is also some research which suggests that folate deficiency can increase your risk of certain cancers, such as colorectal cancer[9].

If you are concerned about your risk of cancer, The TruCheck™ Early Multi-Cancer Screening test can check for the existence of circulating tumour cells in the blood. The test screens for more than 70 types of cancer and has been validated on over 40,000 people.

How can I raise my folate levels quickly?

There are several things you can do to help increase your folate levels, including:

  • Eating rich sources of dietary folate, such as dark green leafy vegetables, broccoli, Brussels sprouts, peas, chickpeas and beans.
  • Supplementation. Pregnant women or women who are looking to get pregnant are advised to take a daily 400 microgram (mcg) folic acid supplement until the 12th week of pregnancy.

What Causes High Folate?

High folate levels can be caused by taking high doses of folic acid supplements or increased consumption of fortified foods. This causes a build-up of unmetabolised folic acid or UMFA in the blood[10]. However, this accumulation doesn’t occur when you eat foods that are naturally rich in folate.

However, high folate levels may pose some risks. For example, masking a vitamin B12 deficiency[11].

What are the side effects of too much folate?

  • Feeling sick (nausea)
  • Diarrhoea
  • Upset stomach
  • Irritability
  • Confusion
  • Skin reactions like itchy, red, or peeling skin
  • Seizures

How to Get More Folate (Folic Acid)?

If you are not pregnant or trying for a baby, the best way to ensure you’re getting enough folate is to eat a healthy, balanced diet that incorporates folate-rich food sources. Because your body is unable to store folate, you must get it from your diet every day to keep your levels topped up.

Folate is found in:

  • Lambs liver
  • Beef
  • Bovril
  • Marmite
  • Eggs
  • Fish
  • Green leafy vegetables, including broccoli, Brussel sprouts, kale, lettuce, peas, rocket, spinach, spring onions, and watercress
  • Pulses including chickpeas, lentils, black-eyed beans, kidney beans
  • Fruit such as avocados, bananas, oranges, honeydew melons, berries
  • Wholemeal flour
  • Fortified breakfast cereals[12]

Are bananas high in folate?

Bananas are a rich source of folate containing approximately 24 mcg per serving[13].

Are eggs high in folate?

Eggs can be a good source of folate, vitamin D and protein. One large egg can contain up to 22 µg of folate[14].

Is cheese a good source of folate?

Milk and cheese can be good sources of folate, particularly mould cheeses, fermented milk drinks, and cottage cheese[15].

Folic acid supplements

If your folate levels are low, you might consider taking a folic acid supplement or your doctor might prescribe them to you.

Is folate and folic acid the same thing?

Folic acid is the man-made or synthetic form of folate found in vitamin supplements and fortified foods[16].

Who needs folate the most?

Most people will get all the folate they need from their diet, but folic acid supplements are recommended for women who are planning to get pregnant or who fall pregnant.

The NHS recommends that women should start taking a folic acid supplement as soon as they start trying for a baby. Ideally, that should be 3 months before conception and up until the 12th week of pregnancy. Folic acid supplementation should help the baby’s brain and spine develop normally and prevent neural tube defects.

The recommended dose is 400 mcg per day, but your doctor may advise taking an increased dose if you are at a greater risk of having a baby with a neural tube defect[17].

Who should not take folic acid?

Folic acid supplements may not be suitable for everyone and you should discuss with your doctor if you have:

  • Ever had an allergic reaction to folic acid or any other medicines
  • Cancer
  • Low vitamin B12 levels or pernicious anaemia
  • A stent fitted in your heart
  • Haemodialysis, a type of kidney dialysis

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

- Health scores calculated


Article references

  1. Duthie, S.J. et al. (2002) ‘Impact of folate deficiency on DNA stability’, The Journal of Nutrition, 132(8). doi:10.1093/jn/132.8.2444s.

  2. Homocysteine lowering with folic acid and B vitamins in vascular disease’ (2006) New England Journal of Medicine, 354(15), pp. 1567–1577. doi:10.1056/nejmoa060900.

  3. Epstein-Peterson, Z.D. et al. (2018) ‘Folate testing and deficiency in hospitalized cancer patients’, Blood, 132(Supplement 1), pp. 5814–5814. doi:10.1182/blood-2018-99-117073.

  4. Kowalska, M., & Cichosz, G. (2014). Produkty mleczarskie jako źródło folianów [Dairy products as source of folates]. Polski merkuriusz lekarski : organ Polskiego Towarzystwa Lekarskiego, 36(214), 287–290.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services