Safety · Supplement
Folate (B9): side effects, safety & interactions
Safe at typical doses. The main caution is masking B12 deficiency (see B12). Very high folic-acid intakes and unmetaboli
- Overall grade
- Grade A
- Last revised
- 0
- graded outcomes
- 0
- references listed
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What is uncertain
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- Watch with Vitamin B12: Folate can mask B12-deficiency anemia; assess B12 alongside.
The evidence in words
Safety profile
Safe at typical doses. The main caution is masking B12 deficiency (see B12). Very high folic-acid intakes and unmetabolized folic acid are debated but not clearly harmful at supplemental doses.
Interactions to respect
Vitamin B12 — Folate can mask B12-deficiency anemia; assess B12 alongside.
What Folate (B9) is
Folate is the B-vitamin required for DNA synthesis and one-carbon metabolism. 'Folate' is the natural food form; 'folic acid' is the synthetic form used in fortification and most supplements. It is most consequential in the weeks around conception and early pregnancy.
The honest bottom line
If pregnancy is possible, 400 µg folic acid daily, starting before conception, is one of the best-evidenced supplements in existence. Outside that context it mainly corrects a dietary gap.
Related reading
Entries that share this one's tags or conditions.
- Choline: side effects, safety & interactionsHigh doses cause fishy odor and GI effects; very high intakes may raise TMAO.Evidence grade B
- Folate (B9)Prevents neural-tube defects — the one supplement with an unambiguous public-health mandate before and in early pregnancy.Evidence grade A
- Folate (B9) for Cardiovascular eventsEvidence grade D — Homocysteine lowering did not cut eventsEvidence grade D
- Folate (B9) for Homocysteine loweringEvidence grade A — Reliable biomarker effectEvidence grade A
Sources
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Last revised . A grade is this entry's reading of the evidence, not medical advice.