Folate (Folic Acid)

What is folate?

Folate, also known as vitamin B9, is a water-soluble B vitamin found naturally in a wide range of foods, particularly leafy green vegetables (spinach, kale, broccoli), legumes (lentils, chickpeas, kidney beans), citrus fruits, nuts, seeds, and liver. Folic acid is the synthetic, more bioavailable form used in dietary supplements and food fortification products.

Folate is essential for the synthesis of nucleotides — the building blocks of DNA — and therefore for cell division and growth. It works closely with vitamin B12 in the one-carbon metabolic cycle, which is central to DNA methylation, amino acid metabolism, and the conversion of homocysteine to methionine. Deficiency of either vitamin produces almost identical haematological effects: impaired DNA synthesis causes red blood cells to become large and dysfunctional, a pattern called megaloblastic anaemia.

Folate's most critical clinical application is in pregnancy. The neural tube — the structure that develops into the brain and spinal cord — closes within the first 28 days of embryonic development, often before a woman knows she is pregnant. Folate deficiency during this window significantly increases the risk of neural tube defects (NTDs) such as spina bifida. The NHS therefore recommends that all women planning a pregnancy and those in the first 12 weeks of pregnancy take 400 µg of folic acid daily as a supplement.

Serum folate reflects recent dietary intake, while red cell folate — measured from inside the red blood cells — reflects longer-term tissue stores and is less influenced by what you ate yesterday. Clinicians may measure one or both depending on the clinical question.

Normal reference range

• Serum folate (normal): 3.0–17.0 µg/L
• Red cell folate (normal): 150–700 nmol/L

Important: Reference ranges vary between laboratories and depend on individual factors including age, sex, pregnancy status, and medication. Always interpret your result in the context of a clinician review. The Vesey reviews every result before release.

What low folate may indicate

Low folate most commonly reflects inadequate dietary intake, increased demand, malabsorption, or medication interference. Important causes include:

• Poor diet — low intake of vegetables, pulses, and fresh fruit; overcooking destroys folate in food
• Alcohol misuse — alcohol interferes with folate absorption and increases renal folate excretion; alcoholic liver disease depletes folate stores
• Malabsorption — coeliac disease (folate is absorbed in the proximal small intestine, the primary site of coeliac damage), inflammatory bowel disease, and tropical sprue
• Pregnancy and lactation — increased demands for fetal cell division and growth rapidly deplete maternal stores
• Methotrexate — deliberately blocks dihydrofolate reductase; used therapeutically in rheumatoid arthritis, psoriasis, and cancer, but causes folate depletion requiring folic acid supplementation on non-treatment days
• Other drugs — phenytoin, carbamazepine, sulfasalazine, trimethoprim, and nitrous oxide (recreational or anaesthetic) can all impair folate metabolism
• Haemodialysis — folate is lost during dialysis sessions

Clinical consequences of folate deficiency include megaloblastic anaemia (fatigue, breathlessness, pallor), glossitis, mouth ulcers, and elevated homocysteine (which is associated with cardiovascular risk and pregnancy complications).

What high folate indicates

Serum folate above the upper reference limit is almost invariably due to supplementation with folic acid or a B-complex vitamin. High folate from supplementation is generally considered harmless. At very high intakes, there is theoretical concern that folic acid supplementation might mask vitamin B12 deficiency by correcting the anaemia while neurological damage from B12 deficiency continues — a reason why B12 is routinely tested alongside folate when investigating megaloblastic anaemia.

Get tested at The Vesey, Sutton Coldfield

Folate is measured within the following panels at The Vesey Private Hospital:

• Nutritional Health panel — folate, B12, vitamin D, ferritin, and other key nutrients
• Vitamins & Minerals panel — comprehensive micronutrient screen
• Anaemia Profile — folate alongside B12, ferritin, haemoglobin, and iron studies

Results are reviewed by a clinician before secure release, typically within 24 hours. Appointments available Monday–Saturday in Sutton Coldfield.

Frequently asked questions

What is a normal folate level?

Normal serum folate is 3.0–17.0 µg/L. Red cell folate (a more stable measure of tissue stores) normally ranges from 150–700 nmol/L. Serum folate reflects recent dietary intake and can fall quickly with a few days of poor diet, while red cell folate is a better indicator of chronic status.

Why is folate important in pregnancy?

Adequate folate is essential for neural tube closure in the first 28 days of embryonic development — before most women know they are pregnant. Deficiency during this window significantly increases the risk of neural tube defects such as spina bifida. The NHS recommends 400 µg of folic acid daily from before conception through to 12 weeks of pregnancy.

What is the difference between folate and folic acid?

Folate is the naturally occurring form of vitamin B9 in food. Folic acid is the synthetic form in supplements and fortified foods — it is more stable and slightly more bioavailable, but requires an enzymatic conversion step to become active. In clinical practice the terms are often used interchangeably.

What medications affect folate levels?

Methotrexate is the most important — it blocks folate metabolism intentionally and requires supplementary folic acid on non-treatment days. Phenytoin, carbamazepine, sulfasalazine, and trimethoprim can also lower folate. Inform your clinician of all medications when discussing your folate result.

Can I correct low folate with diet alone?

For mild deficiency due to poor diet, improving intake of leafy greens, legumes, and fortified foods is the first step. However, folic acid supplementation (400–5000 µg daily depending on the clinical indication) is usually recommended for confirmed deficiency, women planning pregnancy, or those with malabsorption — because dietary folate is easily destroyed by cooking and absorption is less predictable than from supplements.