Some everyday prescriptions lower B vitamin levels, and a few B vitamins can affect how certain drugs work.
Written by Vita Globe Editorial Team | Reviewed against NIH Office of Dietary Supplements guidance | Updated October 7, 2026
Quick Answer
Metformin and stomach acid reducers can lower B12[1]. Some seizure medicines lower folate, B6 and biotin[2][3][4]. Folate can interfere with methotrexate used for cancer, and it can lower blood levels of some seizure medicines[2]. Biotin can throw off lab tests[4]. Always tell your doctor and pharmacist about every supplement you take.
In this article
Which medications lower B vitamins?
- Metformin: may reduce B12 absorption and significantly lower B12 levels[1].
- Proton pump inhibitors (omeprazole, lansoprazole) and H2 blockers (famotidine, cimetidine): reduce stomach acid, which lowers B12 absorption from food[1].
- Seizure medicines such as phenytoin, carbamazepine and valproate: can lower folate and B6, and long-term use is linked to lower biotin[2][3][4].
- Sulfasalazine (for ulcerative colitis and arthritis): reduces folate absorption[2].
- Isoniazid (for tuberculosis): interferes with niacin and B6[5].
- Theophylline (for asthma and COPD): linked to low B6[3].
Which medications can B vitamins affect?
- Methotrexate for cancer: folate can interfere with its effect, so talk to your oncologist first. For rheumatoid arthritis or psoriasis, doctors sometimes prescribe folate to reduce side effects[2].
- Seizure medicines: folate supplements may lower blood levels of phenytoin and similar drugs. High-dose B6 (200mg a day) may lower phenytoin and phenobarbital levels[2][3].
- Diabetes medications: high-dose nicotinic acid (not niacinamide) can raise blood sugar[5].
- Lab tests: biotin can cause false thyroid and troponin results[4].
What should you ask your pharmacist?
- Does any medication I take lower B12, folate or B6?
- Should I have my B12 checked, and how often?
- Is it OK to take a B complex with my prescriptions, and at what time of day?
- Should I stop biotin before my next blood test?
Our option
Vita Globe Vitamin B Complex Gummies
Everyday-dose B vitamins with flush-free niacinamide. Bring the label to your pharmacist so they can check it against your prescriptions.
Frequently asked questions
Can I take B complex with birth control?
Generally yes, but ask your pharmacist about your specific prescription.
I take metformin. Do I need B12?
Ask your doctor about checking your B12 level. Many people on long-term metformin are tested periodically.
Should I space B complex away from my medications?
Your pharmacist can tell you if timing matters for anything you take.
Sources
- NIH ODS. Vitamin B12 Fact Sheet for Health Professionals. ods.od.nih.gov
- NIH ODS. Folate Fact Sheet for Health Professionals. ods.od.nih.gov
- NIH ODS. Vitamin B6 Fact Sheet for Health Professionals. ods.od.nih.gov
- NIH ODS. Biotin Fact Sheet for Health Professionals. ods.od.nih.gov
- NIH ODS. Niacin Fact Sheet for Health Professionals. ods.od.nih.gov
About the Vita Globe Editorial Team
The Vita Globe Editorial Team researches and writes our wellness content from peer-reviewed research and guidance from bodies such as the NIH and FDA. We cite sources inline and update articles when the evidence changes.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for medical advice. Talk to your healthcare provider before starting any new supplement, particularly if you are pregnant, nursing, taking medication, or managing a health condition.
