Questions to Ask Your Clinician or Pharmacist About Antioxidant Supplements

Why bring questions

The FDA advises people to talk to their doctor, pharmacist or other health care professional before deciding to purchase or use a dietary supplement, for example because some supplements might interact with medicines or other supplements. [1] This page is a question list, not advice. It cannot tell you whether a supplement is right for you; your clinician knows your medicines and health history.

If you or someone else may have swallowed too much of a supplement, call Poison Help at 1-800-222-1222 (US), or 911 in an emergency. Other countries: poison help by country.

Bring this with you

• A list of every supplement and medicine you use, including doses and how many times a day, and the bottles or photos of the labels. The FDA suggests bringing such a list at every visit. [2]
• Any change in your health, especially if you are pregnant, breastfeeding, or have had a recent illness or surgery. [2]
• The reason you are considering the supplement (what you hope it will do), so your clinician can say whether evidence exists for that purpose.

Questions about the purpose

1. Is there good evidence that this ingredient helps with what I want it for, or is the claim mostly marketing? A National Cancer Institute review found that nine randomized trials of dietary antioxidant supplements did not provide evidence of benefit for preventing cancer. [3] For the wider picture see do antioxidant supplements work.
2. Do I have a test result or a diagnosis that this is meant to address? Home kits and "antioxidant status" tests are covered at antioxidant status tests.
3. Would more of the food sources be a better first step for me? See antioxidant foods vs supplements.

Questions about medicines

1. Could this change how any of my medicines work? Certain supplements can change absorption, metabolism or excretion of a medicine, so the medicine may become too strong or too weak. [2]
2. I take a blood thinner or aspirin. Is vitamin E or anything else in this product a concern? Warfarin, ginkgo, aspirin and vitamin E can each thin the blood. [2]
3. I use insulin, a diabetes medicine or a cholesterol medicine. Does the ingredient matter? CoQ10 may interact with warfarin and insulin. [4] A pharmacy-focused review lists alpha-lipoic acid among natural health products with blood sugar effects and raises the potential for added low blood sugar when used with conventional medicines. [5] Case reports link alpha-lipoic acid to a rare condition with recurrent low blood sugar. [6] Green tea extract can lower blood levels of atorvastatin. [7]
4. Does this supplement affect my other treatment? See antioxidants and medicines.

Do not stop or change a prescribed medicine on your own; ask the prescriber.

Questions about your health conditions

1. I smoke, used to smoke, or worked around asbestos. Is any beta-carotene in the product a concern? The ATBC trial found a higher lung cancer incidence with beta-carotene in male smokers, and CARET (smokers, former smokers and asbestos-exposed workers) was stopped early with higher lung cancer risk in the supplement group. [8] [9] The National Eye Institute says current and former smokers should avoid the AREDS formula with beta-carotene. [10]
2. I have, or have had, cancer, or I am having treatment. Should my oncology team review this first? CoQ10 may not be compatible with some types of cancer treatment. [4] Some trials found worse outcomes with antioxidant supplements during cancer therapy, especially in smokers, and patients should tell their doctors about any supplement. [3] See antioxidants and cancer: prevention trials and treatment cautions.
3. I have liver or kidney disease. Is this ingredient or product type a concern? Liver injury has been reported with some green tea extracts and with some bioavailable curcumin formulations. [7] [11] The sources we read for this page do not give a kidney rule; ask. See surgery, kidney and liver disease.
4. I have heart disease or diabetes. HOPE-TOO, a long vitamin E trial in people with vascular disease or diabetes, found no prevention of cancer or major cardiovascular events and a possible higher heart failure risk. [12] Is vitamin E a concern for me?
5. I have an eye condition. The AREDS2 trial included only people with intermediate macular degeneration in both eyes, or intermediate in one eye and advanced in the other, and the formulas do not prevent the disease from starting. [10] Does that apply to me?

Questions about surgery

1. I have an operation or procedure coming up. What should I tell the team, and when? NCCIH advises telling providers about all supplements as far in advance as possible; certain supplements may increase the risk of bleeding or affect response to anesthesia. [13]

Questions about the product

1. How can I tell what is actually in this product? What is on the label may not be what is in the product, and "standardized" or "certified" does not guarantee quality. [13] See the label checklist and quality testing.
2. Which form was used in the research for my purpose, and does this product match it? Trial amounts are on the study amounts table; they are not recommendations.
3. How will we know if it is causing problems, and who do I contact? NCCIH advises contacting your health care provider if you have side effects. [13]

After the visit

Write down what your clinician or pharmacist says and keep your supplement list up to date. MedlinePlus advises telling your health care provider about any dietary supplements you use. [15]