Does folate interact with any medications?

People taking methotrexate for cancer should consult their oncologist before folate supplements, which could interfere with the drug's anticancer effect.

What this means for you

The interaction here is specific and it is worth stating precisely, because a vague version of it frightens the wrong people.

People taking methotrexate for cancer should speak to their oncologist before taking folate supplements, because folate could interfere with how the drug works against the tumour.

That is a different situation from the low-dose folic acid that is often prescribed alongside methotrexate for rheumatoid arthritis and psoriasis, where it is given deliberately to reduce side effects. If your rheumatologist put you on folic acid, they meant to.

Separately, and not a drug interaction: large amounts of folic acid can mask a vitamin B12 deficiency by correcting the anaemia while nerve damage continues underneath. That is an argument for checking B12, especially in older adults.

One more reason the B12 point above matters. Folic acid is the one supplement with a genuinely large benefit for a specific group, and the recommendation for anyone who could become pregnant is 400 micrograms a day, based on reviews covering 296,816 women. Doses far above that have not been shown to add anything, and they are what turns the B12 masking problem from theoretical into real. the full review is here.

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.

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