Supplements before blood test can influence the measurements your clinician receives. In some cases, compounds in supplements interact with laboratory assays or affect sample integrity, leading to readings that don’t reflect your baseline. This page covers supplements before blood test, what to take, what to avoid, and how to plan so you get accurate results when you test. Common examples of supplements that can skew results include high-dose biotin, which can cause erroneous readings in certain immunoassays; iron-containing products that can alter iron studies; vitamin C in large amounts that may affect specific chemistry tests; calcium-based supplements that can interfere with some assays; and omega-3 fatty acids that can influence lipid panel measurements. The exact impact depends on the test method used by the lab, so results may vary from one test to another. What to take and what to avoid depends on the test you are having. Start by reviewing the test instructions and discussing your current supplement list with your clinician or the lab. You may be advised to pause certain items for a short period before the draw, especially biotin and high-dose supplements. Typical guidance mentions pausing biotin for about 48 hours; other items may require a longer or shorter window depending on the test. Do not make changes without professional guidance. How to ensure accurate results before you test starts with clear communication and planning. Bring a current list of all supplements and dosages to your appointment, and confirm whether any should be held prior to the blood draw. If you must take supplements, time them away from the draw as instructed by your clinician or lab. Finally, avoid starting new supplements in the days leading up to testing, and request that the lab note any supplements on the order to help interpret the results.
