What are the signs of folate deficiency?

The main clinical sign of folate deficiency is megaloblastic anaemia, in which red blood cells are large and abnormal.

Who is most likely to run low

Folate deficiency also causes a sore tongue and mouth ulcers, changes in skin, hair and nail colour, digestive symptoms and raised homocysteine.

What this means for you

Folate deficiency shows up in the blood before it shows up anywhere else, and the specific sign is a particular kind of anaemia.

Established. The main clinical sign is megaloblastic anaemia, in which red blood cells are large and abnormal. Its symptoms are weakness, fatigue, trouble concentrating, irritability, headache, palpitations and breathlessness. Folate deficiency also causes a sore tongue and shallow mouth ulcers, changes in skin, hair or nail colour, digestive symptoms and raised homocysteine in the blood.

That list overlaps almost exactly with vitamin B12 deficiency, and the overlap is the important part of this page.

Not for everyone. Folic acid in large amounts can correct the anaemia of B12 deficiency while the nerve damage continues underneath. A blood count that looks better is not the same as a problem that has been fixed. If anaemia is found, both vitamins should be checked before either is treated.

Who runs low

People with alcohol use disorder, where absorption falls, breakdown speeds up and losses in urine rise. People with coeliac disease or another malabsorptive condition. Pregnant women and women of childbearing age, because the requirement is higher. And people with an MTHFR variant, which changes how folate is processed.

That last one needs a sentence of its own, because the test for it is sold widely. The review that looked hardest says in as many words that choosing a folate supplement by genotype is a research question rather than advice. People carrying two copies of the 677 variant may show a larger homocysteine response to folic acid, the pattern was not consistent within every trial, and no pooled genotype trend could be estimated at all. The reviewers call it a basis for confirmatory trials in those carriers. If you have already had the test done, take the result to a doctor rather than to a supplement shop.

One group has a reason to act before any symptom appears. Pooling ten systematic reviews covering 296,816 women, folic acid before conception cut neural tube defects to less than half, and the neural tube closes before most people know they are pregnant.

The requirement is 400 micrograms a day and 600 in pregnancy. Lentils, beans, leafy greens, asparagus, avocado and fortified grain cover it. For anyone who could become pregnant the advice is different in kind rather than in degree, because the 400 micrograms has to be in place before conception. The evidence on that is a page of its own.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Where to get it from food

• Cornmeal, degermed, white fortified — 526 µg per 1 cup (131% DV)
• Cornmeal, degermed, yellow fortified — 526 µg per 1 cup (131% DV)
• Chicken, liver, all classes, cooked — 491.3 µg per 3 oz (123% DV)
• Edamame, frozen, prepared — 482.1 µg per 1 cup (121% DV)
• Lentils, mature seeds, cooked, boiled — 358.4 µg per 1 cup (90% DV)

All folate sources ranked →

Full guide: Folate and folic acid: the clearest success in nutrition policy, and its one side effect