Vitamin B complex supplements can interact with several common prescription medications, potentially altering drug efficacy or nutrient absorption. For example, high doses of vitamin B6 can interfere with certain anti-seizure medications, while supplemental niacin or folic acid can interact with cholesterol-lowering drugs, blood pressure medications, or chemotherapy treatments. It is critical to disclose all active over-the-counter supplements and prescription drugs to your physician or pharmacist to prevent adverse metabolic interactions.