Folate Deficiency Symptoms: How It Differs From B12, and the Test

Folate deficiency shows as the symptoms of anaemia: feeling weak or tired, rapid breathing or shortness of breath, headaches, palpitations, indigestion, loss of appetite, diarrhoea, a sore or red tongue sometimes with mouth ulcers, problems with vision, and problems with memory, understanding and judgement; the NHS gives one list for folate and vitamin B12 deficiency because, in its words, most symptoms are the same whichever vitamin is short.¹ What separates them is the nervous system. Numbness, pins and needles, problems with balance and coordination, muscle weakness and incontinence are the B12 deficiency symptoms; folate deficiency causes them far less often.^{1, 2} The common causes are a diet short of green vegetables, pulses and fortified foods, heavy drinking, coeliac disease, pregnancy and a handful of medicines, methotrexate among them.³ A blood test settles it, and the rule that matters is that your GP checks B12 before prescribing folic acid, because folic acid can ease the anaemia while an unrecognised B12 deficiency goes on damaging nerves.⁴ Foods high in folate has the UK portions; the vitamins and minerals guide the units.

Evidence at a glance

• Symptoms and causes: NHS pages on vitamin B12 or folate deficiency anaemia, reviewed 20 February 2023.^{1, 3}
• Testing: the British Society for Haematology guideline finds serum folate as good as red cell folate as the first-line test, with no single gold-standard test for B12 and local reference ranges rather than one cut-off.⁵
• Treatment: daily folic acid tablets, usually for about four months, with B12 checked first and a blood test 7 to 10 days after starting.⁴
• Nerve damage: a neurology review finds the two deficiencies produce identical anaemia and overlapping brain symptoms, with neuropathy less common in folate deficiency.²

Sources checked on 2 November 2026.

What does folate do, and why does its lack show quickly?

Folate, vitamin B9, is needed wherever cells divide: in bone marrow making red blood cells, in the gut lining, in an embryo. It works alongside vitamin B12 in the chemistry that builds DNA, so a shortage of either produces the same large, fragile, scarce red cells, megaloblastic anaemia, and the same tiredness and breathlessness.² The two differ in reserve. B12 is stored in the liver for years, so its deficiency builds silently; folate stores are modest, which is why the NHS treatment course to rebuild them is measured in months and why a diet that drops vegetables, or a demand that rises in pregnancy, can show within a season.^{4, 6} Folate contributes to normal blood formation, to normal psychological function, to reduction of tiredness and fatigue and to maternal tissue growth during pregnancy, its authorised roles, and the symptom list below is what each of them looks like in reverse. What folic acid does for a woman covers the pregnancy side.

What are the symptoms of folate deficiency?

The NHS list, which it applies to both deficiencies: rapid breathing or shortness of breath, headaches, indigestion, loss of appetite, palpitations, problems with your vision, feeling weak or tired, diarrhoea, a sore or red tongue sometimes with mouth ulcers, and problems with memory, understanding and judgement.¹ In practice the first two people notice are tiredness that sleep does not fix and finding stairs harder, both from anaemia; the mouth signs and the appetite loss follow, and the changes in concentration and mood can be marked in older adults. The NHS advises seeing a GP if you have these symptoms, because some of the damage from an untreated deficiency can be irreversible and the longer it goes untreated the higher that chance.¹ Severe anaemia of either kind also puts adults at risk of heart failure, and the NHS lists nervous system problems, temporary infertility, heart conditions and pregnancy complications among the possible complications of the untreated condition.¹

Folate or B12 deficiency: how do you tell?

Not from the anaemia symptoms, which is why both vitamins are tested together. The pointers to B12 are neurological: numbness, pins and needles, muscle weakness, problems with balance and coordination, psychological problems ranging from mild depression or anxiety to confusion, and incontinence.¹ The neurology review puts it the same way: the two deficiencies give identical anaemia and overlapping cognitive and mood symptoms, while neuropathy and spinal cord damage are less common with folate deficiency.² Background pointers help too: a vegan diet, age over 65, metformin, long-term acid suppressants, pernicious anaemia or stomach surgery favour B12; heavy drinking, pregnancy, coeliac disease and the medicines below favour folate; restrictive diets can cause both.³ The signs of B12 deficiency sets out the other half.

What causes folate deficiency?

Diet. Not eating enough folate-rich foods such as broccoli, peas and brown rice, which the NHS says is more likely with an unbalanced diet, heavy alcohol use or a restrictive diet.³ Boiling what greens there are halves their folate; the cooking figures are on foods high in folate.

Malabsorption. Usually a digestive condition such as coeliac disease; folate deficiency is sometimes the clue that leads to the diagnosis.³

Excessive urination. Heart failure, acute liver damage and long-term dialysis can flush folate out.³

Medicines. Some anticonvulsants, colestyramine, sulfasalazine and methotrexate lower folate levels or reduce its absorption; the prescriber manages folic acid alongside them, so do not add it yourself.³

Higher need. Pregnancy, cancer, blood disorders such as sickle cell disease, and infection or inflammation raise folate requirements; premature babies are at higher risk.³

What does the blood test show?

Four things: whether haemoglobin is lower than normal, whether the red cells are larger than normal, the level of vitamin B12 and the level of folate.⁷ The haematology guideline finds serum folate as good as red cell folate as the first-line test, and for B12 it finds no single gold-standard test, so it advises local reference ranges rather than one universal cut-off; your laboratory's range decides what counts as low.⁵ The NHS adds a caution: some people have symptoms with normal-looking levels and some have low levels without symptoms, so symptoms are weighed alongside the numbers.⁷ If B12 is also low, it is treated first or at the same time.⁴

How is folate deficiency treated, and how long does recovery take?

With daily folic acid tablets to build folate levels back up, usually for about four months, alongside changes to the diet; where the cause persists, treatment continues for longer, possibly for life.⁴ Before starting, the GP checks B12 levels, because folic acid can ease the symptoms so much that it hides a B12 deficiency that would then harm the nervous system.⁴ Progress is checked with a blood test around 7 to 10 days after starting and often a second at about eight weeks to confirm the treatment has worked; most people need no further monitoring unless symptoms return.⁴ The same logic sets the ceiling for over-the-counter folic acid at 1 mg a day: higher doses can mask the symptoms of B12 deficiency, and a 2024 review of the evidence on excess folic acid in people short of B12 reaches the same conclusion.^{6, 8}

How do you prevent it?

Adults need 200 micrograms of folate a day, met by green vegetables most days, pulses a few times a week, oranges, and fortified breakfast cereals, steamed rather than boiled.⁶ Women who could become pregnant are advised a 400 microgram folic acid supplement until 12 weeks, 5 mg on prescription at higher risk, because folic acid trials reduce neural tube defects.^{6, 9} If you take methotrexate or an anticonvulsant, follow the prescriber's folic acid plan. From 13 December 2026 UK non-wholemeal flour will carry added folic acid, which raises baseline intakes for everyone eating white bread. A B complex at 100 to 200% of the reference intake is a reasonable hedge for a narrow diet, well below the 1 mg ceiling; what B complex is for places folate among the other B vitamins.

What we don't know

• How often folate deficiency alone damages nerves. The review describes neuropathy as less common, not absent; most cases involve B12 too.²
• The right cut-off for serum folate. Laboratories set their own, and no trial has defined the level below which symptoms begin.⁵
• How quickly each symptom resolves. The NHS monitoring timeline tracks blood results, not symptoms.⁴

Frequently asked questions

What are the signs of folic acid deficiency?

Tiredness and weakness, breathlessness, headaches, palpitations, a sore red tongue and mouth ulcers, poor appetite, diarrhoea, vision problems and trouble with memory and concentration.¹

What is the most common cause of folate deficiency?

Diet: too few folate-rich foods, often with heavy drinking or a restrictive eating pattern. Coeliac disease, pregnancy and medicines such as methotrexate follow.³

Is vitamin B12 the same thing as folate?

No. They are different vitamins that work together to make red blood cells, so a shortage of either causes the same anaemia; B12 deficiency also damages nerves, folate deficiency rarely does.^{1, 2}

Can folate deficiency cause memory loss?

Problems with memory, understanding and judgement are on the NHS symptom list for both deficiencies; marked memory change calls for a B12 test as well.¹

Can folic acid hide a B12 deficiency?

At high doses, yes. The NHS says folic acid above 1 mg a day can mask the symptoms of vitamin B12 deficiency, which can eventually damage the nervous system if it is not spotted and treated, and that this is particularly a concern for older people because B12 becomes harder to absorb with age.⁶ Two observational studies show why the concern is taken seriously: among 2,420 US adults aged 60 and over, people with low B12 and high folate were about twice as likely to score low on two cognitive tests as people with low B12 alone (a cross-sectional survey, which cannot show cause; US government funded), and unmetabolised folic acid was found in the fasting blood of 94% of 137 Irish adults aged 60 to 86 in a country with widespread voluntary fortification of foods (a cross-sectional study with non-commercial support).^{10, 11} Keep supplement folic acid under 1 mg unless it is prescribed, and expect your GP to check B12 before treating folate deficiency.^{4, 6}

Sources

1. NHS. Vitamin B12 or folate deficiency anaemia: symptoms. Page reviewed 20 February 2023. nhs.uk.
2. Reynolds EH. The neurology of folic acid deficiency. Handbook of Clinical Neurology, 2014. PubMed 24365361. Narrative review.
3. NHS. Vitamin B12 or folate deficiency anaemia: causes. Page reviewed 20 February 2023. nhs.uk.
4. NHS. Vitamin B12 or folate deficiency anaemia: treatment. Page reviewed 20 February 2023. nhs.uk.
5. Devalia V, Hamilton MS, Molloy AM. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. British Journal of Haematology, 2014. PubMed 24942828. Clinical practice guideline, British Committee for Standards in Haematology.
6. NHS. Vitamins and minerals: B vitamins and folic acid. Page reviewed 3 August 2020. nhs.uk. Great Britain nutrition and health claims register for the authorised wordings.
7. NHS. Vitamin B12 or folate deficiency anaemia: diagnosis. Page reviewed 20 February 2023. nhs.uk.
8. Miller JW, et al. Excess folic acid and vitamin B12 deficiency: clinical implications? Food and Nutrition Bulletin, 2024. PubMed 38987872. Review, US government funded; the first author is co-author of a patent on a vitamin B12 absorption assay.
9. Viswanathan M, et al. Folic acid supplementation to prevent neural tube defects: updated evidence report and systematic review for the US Preventive Services Task Force. JAMA, 2023. PubMed 37526714. Systematic review, US government funded.
10. Bailey RL, et al. High folic acid or folate combined with low vitamin B-12 status: potential but inconsistent association with cognitive function in a nationally representative cross-sectional sample of US older adults participating in the NHANES. American Journal of Clinical Nutrition, 2020. PubMed 32860400. Cross-sectional analysis, 2,420 adults aged 60 and over, NHANES 2011 to 2014; US government funded.
11. Boilson A, et al. Unmetabolized folic acid prevalence is widespread in the older Irish population despite the lack of a mandatory fortification program. American Journal of Clinical Nutrition, 2012. PubMed 22854405. Cross-sectional study, 137 adults aged 60 to 86; non-commercial support listed on PubMed, conflicts not stated.

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This article is general information, not medical advice. Symptoms of anaemia need a GP blood test for folate, B12 and iron together; do not start folic acid for a suspected deficiency before B12 has been checked.