Folate Safety & Side Effects
Our assessment
Based on FDA data, the overall safety profile of folate supplements is well-characterized, but a critical risk exists: taking large amounts can mask a vitamin B12 deficiency by correcting the associated anemia while allowing irreversible nerve damage to progress FDA FAERS ↗. This is the most important safety finding. You should not consume folate from supplements or fortified foods above the upper limit unless recommended by a healthcare provider NIH ODS ↗.
How it works
Folate is a B-vitamin essential for DNA synthesis and cell division. In supplement form, it is used to prevent neural tube defects during pregnancy and to treat certain anemias. The key concern is that high-dose folic acid can correct the blood-related signs of a vitamin B12 deficiency without addressing the underlying nerve damage, which can become permanent if untreated NIH ODS ↗ FDA FAERS ↗.
Safety profile
Folate that is naturally present in food is not harmful NIH ODS ↗. However, specific side effects from FDA adverse event data are not available for this supplement; the primary risk identified is the masking of vitamin B12 deficiency. Data not available for specific adverse event report counts for folate supplements FDA FAERS ↗. The risk is dose-dependent, occurring when folate intake from supplements and fortified foods consistently exceeds the upper limit NIH ODS ↗.
Our recommendation
Be cautious if you are over 50, follow a vegan or vegetarian diet, or have a history of gastrointestinal disorders like Crohn’s disease or celiac disease, as these groups are at higher risk for vitamin B12 deficiency. Folate supplements can also interfere with methotrexate when taken to treat cancer and may interact with antiepileptic medications like phenytoin (Dilantin) and carbamazepine (Carbatrol, Tegretol) FDA FAERS ↗. Always have your vitamin B12 levels checked before starting high-dose folate, and do not exceed the upper limit unless your healthcare provider directs otherwise NIH ODS ↗.
AI-assisted analysis. Data sourced from NIH ODS and FDA.
Safety Overview
Folate that is naturally present in food and beverages is not harmful. However, you should not consume folate in supplements or fortified foods and beverages in amounts above the upper limit, unless recommended by a health care provider. Taking large amounts of folate supplements might hide a vitamin B12 deficiency because these supplements can correct the anemia that the vitamin B12 deficiency causes but not the nerve damage that the vitamin B12 deficiency also causes. The vitamin B12 deficiency can lead to permanent damage of the brain, spinal cord, and nerves . Large doses of folate supplements might also worsen the symptoms of vitamin B12 deficiency. High doses of folic acid might increase the risk of colorectal cancer and possibly other cancers in some people. High doses can also lead to more folic acid in the body than it can use, but whether these increased folic acid levels are harmful is not completely clear. The daily upper limits for folate from supplements and fortified foods and beverages are listed below.
Drug Interactions
Folate supplements can interact with several medications. Here are some examples: Folate supplements could interfere with methotrexate (Rheumatrex, Trexall) when taken to treat cancer. Taking antiepileptic or antiseizure medications, such as phenytoin (Dilantin), carbamazepine (Carbatrol, Tegretol, Equetro, Epitol) and valproate (Depacon), could reduce blood levels of folate. Also, taking folate supplements could reduce blood levels of these medications. Taking sulfasalazine (Azulfidine) for ulcerative colitis could reduce the body’s ability to absorb folate and cause folate deficiency. Tell your doctor, pharmacist , and other health care providers about any dietary supplements and medicines you take. They can tell you if those dietary supplements might interact or interfere with your prescription or over-the-counter medicines or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients.