Folic Acid

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Jan 27, 2023

Warnings

Folic Acid Risks, Warnings, and Complications

Taking folic acid can lead to serious adverse effects in some people. Some of the risks of taking folic acid supplements include:

DIFFICULTY IN DIAGNOSING VITAMIN B12 DEFICIENCY: Low levels of folate and low levels of vitamin B12 can lead to anemia. People with anemia due to vitamin B12 deficiency should not take folic acid. This can make it harder to diagnose the nerve problems caused by low B12 levels. Your doctor can do blood tests to find out the exact cause of your anemia and treat it accordingly.
DRUG INTERACTIONS: Folic acid can interact with certain medications and make them less effective. For example, taking folic acid supplements with methotrexate (Trexall, Rheumatrex), a medicine used to treat cancer and autoimmune diseases, can make this medicine less effective. Taking folic acid supplements can also lower the serum concentration of certain antiepileptic medications like phenytoin (Dilantin), valproate (Depacon), and carbamazepine (Tegretol, Carbatrol). Taking certain medications can lead to a folate deficiency. Check with your healthcare provider before you take folic acid to ensure there are no drug interactions with your other medications. Your doctor may advise you to avoid taking folic acid if there are known interactions with your other medicines. You may need to take folic acid supplementation if your medications cause low folic acid levels.
RISKS ASSOCIATED WITH INJECTABLE FOLIC ACID: The injectable form of folic acid contains small amounts of aluminum which can build up in people with kidney problems and cause brain and bone problems. The risk is particularly high in premature babies who do not have fully functioning kidneys. The injectable form of folic acid also contains benzyl alcohol as a preservative, which can cause gasping syndrome in premature babies. If you have kidney problems, talk to your healthcare provider about the risks of taking folic acid supplementation in the injectable form. If you have a premature baby, talk to your baby’s healthcare team about the risks of injectable folic acid supplements.

Precautions Before Starting Folic Acid

Tell your healthcare provider if you have ever had an allergic reaction to folic acid, any of the active or inactive ingredients in folic acid supplements, or any other medications. Your pharmacy can give you a list of ingredients in folic acid supplements.

Give your doctor and pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, vitamins, supplements, and herbal products. This can help avoid possible drug interactions.

Give your doctor a complete medical history. Folic acid may not be right for people with certain medical conditions, such as low vitamin B12 levels or kidney problems (injectable form).

If you are planning to get pregnant, talk to your doctor about starting a prenatal vitamin that contains folic acid. Taking folic acid supplementation at least one month before becoming pregnant and for the first 12 weeks of a pregnancy can protect your unborn baby against serious birth defects (neural tube defects).

Precautions During Use of Folic Acid

Keep all your healthcare appointments while on folic acid supplementation. Make sure you are not getting more than the recommended upper intake level (1,000 mcg in adults) from folic acid supplements and fortified foods. Stop taking folic acid supplements and call your doctor if you develop signs and symptoms of a serious allergic reaction, such as skin rash, peeling skin, swelling of the face, lips, or throat, chest tightness, or difficulty breathing.

Folic Acid Drug Interactions

Folic acid supplements can interact with certain medications and affect how they work. Some medicines can prevent intestinal absorption of folate and lead to a folate deficiency. Possible interactions between folic acid and other drugs can increase the risk of severe adverse reactions.

The following medications may have interactions with folic acid:

Methotrexate (Trexall, Rheumatrex), a medication used to treat cancer and autoimmune conditions.
Antiepileptic medications like phenytoin (Dilantin), valproate (Depacon), and carbamazepine (Tegretol, Carbatrol).
Sulfasalazine (Azulfidine), a medicine used to treat ulcerative colitis.

The above list may not include all possible interactions of folic acid. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, OTC (non-prescription) medications, dietary supplements, and herbal remedies. Also, tell your healthcare professionals if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with dietary supplements and medications.

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