If you are currently being treated with any of the following medications, you should not use folic acid supplements without first talking to your healthcare provider.

Antibiotics, Tetracycline
Folic acid should not be taken at the same time as the antibiotic tetracycline because it interferes with the absorption and effectiveness of this medication. Folic acid either alone or in combination with other B vitamins should be taken at different times from tetracycline. (All vitamin B complex supplements act in this way and should therefore be taken at different times from tetracycline.)

In addition, long-term use of antibiotics can deplete vitamin B levels in the body, particularly B2, B9, B12, and vitamin H (biotin), which is considered part of the B complex.

Aspirin, Ibuprofen, and Acetaminophen
When taken for long periods of time, these medications, as well as other anti-inflammatories can increase the body's need for folic acid.

Birth Control Medications, Anticonvulsants, and Cholesterol-lowering Medications
Birth control medications, anticonvulsants for seizures (namely, phenytoin and carbamazapine), and cholesterol-lowering medications (namely, bile acid sequestrants including cholestyramine, colestipol, and colesevelam) may reduce the levels of folic acid in the blood as well as the body's ability to use this vitamin. Extra folate when taking any of these medications may be recommended by your healthcare provider. When taking bile acid sequestrants for cholesterol, folate should be taken at a different time of day.

Sulfasalazine
Sulfasalazine, a medication used for ulcerative colitis and Crohn's disease, may reduce the absorption of folic acid, leading to lower levels of folic acid in the blood.

Methotrexate
Methotrexate, a medication used to treat cancer and rheumatoid arthritis, increases the body's need for folic acid. Folic acid reduces the side effects of methotrexate without decreasing its effectiveness.

Other
Antacids, cimetidine, and ranitidine (used for ulcers, heartburn, and related symptoms) as well as metformin (used for diabetes) may inhibit the absorption of folic acid. It is best, therefore, to take folic acid at a different time from any of these medications.

Barbiturates, such as pentobarbital and phenobarbital, used for seizures, may impair folic acid metabolism.