Vitamin B12 and Folate Together: What to Know

Quick answer

Folate and vitamin B12 are partners in the body: both are needed to make DNA and red blood cells, and both take part in turning homocysteine into methionine. Adults need 400 mcg DFE of folate and 2.4 mcg of B12 a day. Large amounts of folic acid can hide a B12 shortfall.^1,2,3

Key facts

Adults need 400 mcg DFE of folate and 2.4 mcg of vitamin B12 a day, from all sources.^1,2
In trials NIH describes, folic acid taken with vitamins B6 and B12 lowered blood homocysteine by 18.5%.³
The adult upper limit of 1,000 mcg a day for folic acid rests on how folate and B12 interact. B12 has no upper limit.^2,3
Large amounts of folic acid can hide the blood changes that low B12 causes while its nerve effects carry on.^1,3
The body holds 15 to 30 mg of folate but 1 to 5 mg of B12, and B12 stores last for years.^2,3

Why these two vitamins are always mentioned together

Folate and vitamin B12 are different molecules from different foods, yet the body uses them in the same chain of reactions. Folate carries small chemical pieces that cells use to build DNA and RNA. B12 is a helper for an enzyme in the same area of chemistry, and both are needed for the step that turns homocysteine, an amino acid in the blood, into methionine.^3,4

That shared step is why one blood marker, homocysteine, rises when either vitamin runs short, and why it cannot say on its own which one is the cause. Both vitamins are also needed for red blood cells to form normally. The cells that become red blood cells divide quickly, so they call heavily on DNA building.^3,4

The two differ in where they come from. Folate is found in leafy vegetables, beans, citrus and liver, and folic acid is added to enriched grains. Vitamin B12 occurs naturally only in animal foods, so fortified foods or supplements matter for people who eat few of them.^1,2

What the evidence shows for each

Each statement below is quoted from our ingredient files with its grade and the amount behind it. They describe what enough of each vitamin does, not what extra does.^5,6

Contributes to normal blood formation*^3,5,7

Moderate evidence

Red blood cells are made from rapidly dividing cells, which need folate to copy their DNA. NIH explains that when this step falters, the body makes red blood cells that are unusually large and abnormal, and the folic acid prescribing label describes an outside source of folate as required to keep red blood cell production normal. The EU permits the statement that folate contributes to normal blood formation.

Amount studied: Recommended intake: 400 mcg DFE a day for adults, from all sources

Contributes to normal red blood cell formation*^4,6

Moderate evidence

NIH lists healthy red blood cell formation among B12's core jobs, and the US recommended amount was set as the intake needed to keep blood counts and blood B12 levels normal. Without enough B12, the body makes large, abnormal red blood cells. The EU permits this statement.

Amount studied: Recommended intake: 2.4 mcg a day for adults, from all sources

Contributes to normal homocysteine metabolism*^3,5

Moderate evidence

Folate is needed to turn homocysteine, an amino acid in the blood, into methionine. In trials summarized by NIH, folic acid lowered blood homocysteine: by 26% in 818 Dutch adults aged 50 to 70 who took 800 mcg a day for 3 years, and by 18.5% in women who took folic acid with vitamins B6 and B12. The EU permits this statement. Homocysteine is a blood marker, and lowering it has not changed most of the long-term health outcomes it was studied for.

Amount studied: 800 mcg of folic acid a day on its own, and up to 2,500 mcg a day combined with vitamins B6 and B12

Taking them at the same time

Neither NIH fact sheet says that one of these vitamins changes how the other is absorbed. They do take different routes into the body, which is why their timing notes look different.^3,4

Taken with food, about 85% of supplemental folic acid is absorbed; taken without food, nearly all of it is.³

Intrinsic factor, the main route for absorbing B12, is saturated at about 1.5 to 2 mcg per meal, so the share absorbed falls as the amount taken at one time rises.^4,8

Neither source names a best hour of the day for either vitamin. What the folate studies do show is that routine matters more than clock time: in a six-month trial in women, one daily dose and four smaller doses gave the same blood folate, and blood folate fell quickly once supplements stopped. B12 behaves the other way, because the body keeps years' worth.^2,9

Amounts side by side

Folate and vitamin B12 for adults, per day^1,2,3,4
	Folate	Vitamin B12
Recommended amount	400 mcg DFE	2.4 mcg
In pregnancy	600 mcg DFE	2.6 mcg
Typical supplement amounts	680 to 1,360 mcg DFE (400 to 800 mcg folic acid)	5 to 25 mcg in multivitamins, 50 to 500 mcg in B complex, 500 to 1,000 mcg in B12 alone
Upper limit	1,000 mcg of folic acid from supplements and fortified foods	None set
Body store	15 to 30 mg	1 to 5 mg

Labels print folate in mcg DFE, a unit that counts folic acid at 1.7 for every 1 taken. A product with 400 mcg of folic acid therefore lists 680 mcg DFE. That is easy to misread as an overdose, and it matters because the upper limit is written in plain mcg of folic acid, not in DFE.³

What’s in ours

Men's Multi: Folate, 680 mcg DFE (400 mcg Folic Acid) per serving, from the label

What’s in ours

Men's Multi: Vitamin B12, 27 mcg per serving, from the label
Ashwagandha Complex: Vitamin B12, 25 mcg per serving, from the label

The caution that belongs to this pair

Large amounts of folic acid can correct the anemia caused by low vitamin B12 without stopping the nerve damage it also causes, so the B12 problem can go unnoticed until the damage is permanent. Large doses might also make the effects of low B12 worse.^1,3,7

The folic acid limit was set on the basis of how folate and B12 interact, and NIH notes that questions about this possibility remain open.³

Groups more likely to run low on B12 include older adults, people who eat no animal foods, and people who take metformin or acid-reducing medicines. NIH puts the share of older adults living at home with low B12 anywhere from 3% to 43%, depending on the definition used.⁴

Your doctor may want to check on you

Metformin may lower vitamin B12 levels, possibly by interfering with its absorption. In 29-week trials described on the metformin label, about 7% of people with normal B12 dropped below normal, and the label tells prescribers to measure B12 every 2 to 3 years.^2,4,10,11

On the medicine's label

Ask first if you plan to take more than 400 mcg of folic acid a day and have never had your B12 checked.³
Ask first if you have numbness or tingling in your hands or feet, balance problems or memory changes. These need testing, not self-treatment.⁴
Ask first if you take methotrexate, an anti-seizure medicine or sulfasalazine, each of which can change how folate is handled.¹
Ask first if you are pregnant, planning a pregnancy or breastfeeding, so the amounts and forms suit you.

Questions people ask

Can you take vitamin B12 and folic acid together?

They are sold together in multivitamins and B complex products, and the NIH sheets do not describe either one changing how the other is absorbed. The caution that does apply is the masking effect of large folic acid amounts, covered above.^3,4

What is the best time to take vitamin B12 and folic acid?

Our sources name no best hour for either. About 85% of folic acid is absorbed with food and nearly all of it without, so either way works, and a steady daily habit matters most.^3,9

Is there a blood test for B12 and folate?

Yes. Doctors usually check B12 in the blood, and most laboratories count results under 200 or 250 pg/mL as low, with methylmalonic acid used to confirm a borderline result. Folate is measured in serum or in red blood cells. Homocysteine rises when either vitamin is short, so it cannot say which one.^3,4

Can folic acid hide a B12 shortfall?

Yes. Large amounts of folic acid can correct the blood changes caused by low B12 without stopping the nerve damage, so the problem can go unnoticed. This is why people with a possible B12 problem should ask a doctor before taking more than 400 mcg of folic acid a day.^1,3

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line Men's Multi Ashwagandha Complex

Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.