Methylfolate vs Folic Acid: 5-MTHF, Pregnancy, MTHFR and B12 (UK)

What is methylfolate?

Methylfolate is 5-methyltetrahydrofolate (5-MTHF), the main form of folate that circulates in your blood. Folate is vitamin B9. In supplements, methylfolate is usually sold as calcium L-methylfolate or as a glucosamine salt, both permitted sources of folate in UK food supplements. It does the same jobs as other forms of folate once in the body.

For how folate fits with the other B vitamins, see our B vitamins guide, which also covers the new flour rules.

Methylfolate vs folic acid: what’s the difference?

Folic acid is a stable, man-made form of folate that the body converts, in several steps, into methylfolate. Methylfolate skips those steps. Both raise blood folate. The key difference is evidence: folic acid has been proven in large trials to prevent neural tube defects such as spina bifida, while methylfolate hasn’t been tested that way.

Is methylfolate better absorbed than folic acid?

Methylfolate raises blood folate at least as well as folic acid. In a 24-week trial of 144 women, red blood cell folate rose more on 416 micrograms of methylfolate than on 400 micrograms of folic acid. A 2025 review of 11 trials found similar results, but none measured whether babies were protected from neural tube defects.

That gap matters. The landmark Medical Research Council trial in 1991 found folic acid cut the risk of a repeat neural tube defect by 72% in women who had had an affected pregnancy. A 2024 review concluded that clinical studies are still needed before methylfolate can be treated as an equal alternative.

Methylfolate in pregnancy: can you take it instead of folic acid?

The NHS advice is folic acid: 400 micrograms a day from before you conceive until 12 weeks, or 5mg if your GP prescribes it. Many pregnancy multivitamins now contain methylfolate, alone or with folic acid. If you’d prefer methylfolate, ask your GP, midwife or pharmacist first, and never swap a prescribed 5mg dose yourself.

The NHS says you need the higher 5mg dose of folic acid if:

• you or the baby’s father has a neural tube defect, or a relative with one
• you’ve had a previous pregnancy affected by a neural tube defect
• you have diabetes
• you have a blood condition such as sickle cell anaemia or thalassaemia
• you take medicine for epilepsy or HIV

Start folic acid before you stop contraception if you can, because the spine forms in the first weeks, often before you know you’re pregnant. If you’re eligible for Healthy Start, you may be able to get free vitamins that include folic acid. Our guide to magnesium in pregnancy covers the other common question we’re asked.

MTHFR and methylfolate: do you need it?

Probably not. MTHFR is a gene for an enzyme in the folate pathway, and common variants such as C677T slightly slow one conversion step. People with these variants can still use folic acid, which still raises their blood folate. Medical experts don’t recommend routine MTHFR testing, and it isn’t part of routine NHS care.

The American College of Medical Genetics and Genomics has said since 2013, and again in 2020, that there’s a lack of evidence for MTHFR variant testing in routine care, including for blood clots and recurrent miscarriage. The US CDC recommends folic acid for everyone who could become pregnant, whatever their MTHFR result.

MTHFR results often come from home DNA kits, and the variants are common, so many people find they carry one. If you’ve been told you have an MTHFR variant, ask your GP or midwife before changing anything. A blood test for folate, vitamin B12 or homocysteine tells a doctor more than the gene test does.

How much methylfolate should you take?

Most methylfolate supplements give 400 to 800 micrograms a day, often listed as micrograms of folate. Adults who aren’t planning a pregnancy need 200 micrograms of folate a day, usually from food. Keep total supplements to 1mg (1,000 micrograms) a day or less, unless a doctor advises more.

• Check the unit: labels may show micrograms of folate or of the methylfolate salt, which weigh slightly differently.
• Add up everything: multivitamins, pregnancy vitamins, B complexes and fortified cereals all count.
• Look for B12: a folate supplement with vitamin B12 makes sense for vegans and older adults.

Our guides to multivitamins and whether you can overdose on vitamins explain how amounts add up across products.

Methylfolate side effects and medicines

Methylfolate is well tolerated at usual doses. Side effects reported with folate supplements include bloating, wind and nausea. The bigger concern is vitamin B12: large amounts of folate can hide the anaemia of B12 deficiency while nerve damage carries on, so check your B12 if you’re vegan, over 60 or take metformin or an acid-reducing medicine.

The NHS says doses of folic acid above 1mg can mask the symptoms of vitamin B12 deficiency, and that older people are at greater risk because B12 absorption falls with age. Folate in any form can correct the anaemia, so the same care applies to methylfolate. See vitamin B12 deficiency symptoms, vitamin B12 supplements and peripheral neuropathy for the signs.

Talk to a doctor or pharmacist before taking any folate supplement if you:

• take methotrexate: folate timing is part of the treatment plan, so don’t add any without asking
• take epilepsy medicines such as phenytoin, phenobarbital or primidone
• take sulfasalazine, lithium, co-trimoxazole or chloramphenicol
• have vitamin B12 deficiency anaemia or pernicious anaemia
• have a coronary stent or cancer, which the NHS lists as reasons to check first

Call 111 if you think you’re having an allergic reaction, and 999 if your lips, mouth, throat or tongue swell or you’re struggling to breathe. In the US, high-dose L-methylfolate (7.5 to 15mg) is prescribed alongside antidepressants; that isn’t standard UK practice, so don’t use methylfolate to treat low mood without your GP.

What can folate supplements claim?

In Great Britain, a supplement that is at least a source of folate can use the authorised folate claims, whatever the form. The specific pregnancy claim about neural tube defects is different: it names folic acid and needs at least 400 micrograms per daily portion, taken from at least one month before to three months after conception.

The authorised folate claims include:

• Folate contributes to maternal tissue growth during pregnancy.
• Folate contributes to normal blood formation.
• Folate contributes to normal homocysteine metabolism.
• Folate contributes to normal psychological function.
• Folate contributes to the reduction of tiredness and fatigue.
• Folate has a role in the process of cell division.

The pregnancy claim reads: “Supplemental folic acid intake increases maternal folate status. Low maternal folate status is a risk factor in the development of neural tube defects in the developing foetus.” Treat any methylfolate product that claims to prevent spina bifida with caution.