Why You Need to Talk to Your Doctor Before Taking Supplements

Although Health Canada assures Canadians have access to natural health products that are safe, effective, and of high quality, that doesn’t mean all supplements and natural remedies are safe for you. “Supplements may carry harmful risks such as inaccurate dosing information,” says Wendy Kaplan, MS, RDN, a dietitian in Long Island, New York.

That’s why smart supplement shopping is so important. “If you’re not sure about the safety of an ingredient, the first thing you should do is talk to your doctor or pharmacist,” notes John Travis, a senior research scientist at NSF International, a global public health and safety organization.

Here are additional reasons to chat with your doctor before you start taking supplements. (Consider asking your doctor about these five supplements women often need.)

1. You may not need the supplement you think you need. 

Self-diagnosing isn’t necessarily the best strategy. While if you’re pregnant, it may be a no-brainer that you need a prenatal vitamin, not everyone needs to supplement with vitamins such as vitamin D or vitamin B12. (See if it’s important to take a daily vitamin.) “A supplement, just from the word itself, is meant to supplement or augment any vitamin or mineral you might be lacking or not having enough of,” says Robert Segal, MD, founder of Medical Offices of Manhattan in New York City. “Your doctor can recommend a blood test to find out which (if any) vitamins or minerals you may have deficiencies of.”

2. You can get the intel on supplement benefits.

“Ongoing research shows some supplements can have striking health benefits,” says William Li, MD, author of Eat to Beat Disease. “For example, a supplement formulation called AREDS may reduce the risk of vision loss from a condition called age-related macular degeneration. Fish oil supplements containing omega-3 fatty acids can lower risk factors for heart disease, and supplements containing prebiotics and probiotics are looking like they may be future game-changers for health as we begin to understand how our gut microbiome defends us against chronic diseases.” Discuss your specific health concerns and family history with your doctor.

3. Supplements may have unproven claims.

“Some dietary supplements make claims that are either not well substantiated or have no data to back up the specific claim,” says Marilyn Schorin, PhD, RDN, a dietitian in Louisville, Kentucky. “Some claims are very vague—such as helping brain health or boosting immunity—so your perceived benefit may vary substantially from the studies used to support the claim. Your doctor or health professional can help to sort the benefit from bluster.” Registered dietitians tend to be especially schooled in supplement knowledge.

4. A supplement could be detrimental to your health.

“It is not a good idea to just add supplements without discussing with your doctor and knowing what you need,” says Melissa Altman-Traub, MS, RDN, a dietitian in Jamison, Pennsylvania. “For example, if a person feels tired and decides to take an iron supplement to treat that, she may not know if she has a hereditary condition that causes her to absorb more iron and accumulate it. The excess iron could cause organ damage, and the original cause of the fatigue would go untreated.”

Furthermore, “many supplements have complicated names, and some potentially dangerous ingredients are listed under names that make them seem like safer, natural products,” says Travis. “For example, harmful compounds such as DMAA, DMBA, and DEPEA have been deceptively labeled as botanical extracts like geranium oil and dendrobium extract.” DMAA, for example, is an amphetamine that can cause health problems as serious as a heart attack.

5. A supplement can contain fillers that don’t agree with you.

It’s common to look at a supplement but not the filler ingredients it contains. These ingredients may be problematic for certain people. For instance, they may contain inactive ingredients that pose a risk to someone with celiac disease. “It’s important for people to remember that not all supplements are created equally, and there can be added fillers, sugars, or other ingredients in supplements in addition to what you think you are taking,” says Nicole Avena, PhD, assistant professor of neuroscience at Mount Sinai School of Medicine, in New York City. “This is why it is important to review the ingredients list of any products you plan to take with your doctor to ensure that all are safe and won’t interact with anything in your personal medical history.”

6. You could end up taking in toxic levels.

It may sound like a great idea to take a supplement such as vitamin A. But your body stores the fat-soluble vitamins A, D, E, and K—and you can easily overdo it. “Certain supplements may contain excessive amounts of vitamins and minerals, and if taken every day they can accumulate into toxic levels,” says Allie Hosmer, MS, RDN, a dietitian in Washington, D.C. Minerals can also accumulate in your body. “You could be feeling nauseous due to excess iron intake,” adds Segal.

7. You must take precautions before surgery.

Having surgery in the near future? Disclosing your supplement regimen to your doctors and surgical team is of the utmost importance. This is because certain supplements may increase your risk of bleeding during surgery. This list includes gingko biloba, milk thistle, and turmeric, according to the Stanford University School of Medicine. Your doctor will likely tell you to stop taking such supplements a certain amount of time before surgery.

8. Your supplements and meds could interact badly.

“Because dietary supplements are mainly sold over the counter, it is very easy to start and stop dietary supplementation without your doctor’s knowledge,” says Sophia O. Tolliver, MD, MPH, family medicine physician at The Ohio State University Wexner Medical Center, in Columbus, Ohio. “Depending on the complexity of your health history, you could be at risk for medication interactions with unknown dietary supplementation.” Case in point: If you’re taking the blood thinner Warfarin, your doctor may advise against taking vitamin A, vitamin E, or garlic supplements. These can thin the blood—and when coupled with Warfarin, may make bleeding more likely, notes Dr. Li.

9. Interactions may make you feel sick.

Even if you’re taking a short-term medication, such as an antibiotic, let your doctor know about your supplement routine. Here’s an example: “Combining magnesium and an anti-hypertensive medication could potentially have added effects, making a patient lightheaded, dizzy, or even faint,” says Lauren Tessier, ND, a naturopathic physician in Waterbury, Vermont. See the supplement or medication combos you should never mix.

10. Supplements can make meds less effective.

“St. John’s Wort is often hailed for it’s used for depression,” says Joan Salge Blake, EdD, RDN, a nutrition professor at Boston University and host of the health and wellness podcast SpotOn! “Unfortunately, this supplement can weaken the effects of many medicines, including crucially important ones such as birth control pills.” Many, many other potential interactions exist—for instance, vitamin K1 can counteract Warfarin, notes Adam Splaver, MD, a cardiologist in Hollywood, Florida. So always give your doctor a full list of every single medicine and supplement you take, even if you take them infrequently.

11. You could land in the emergency room.

More than 23,000 emergency room visits per year are linked with negative effects from supplements, per a study in the New England Journal of Medicine. If you tell your doctor everything you’re taking, she could advise you to stop a supplement that’s dangerous, pronto. “Having a discussion with your doctor about dietary supplements will help to flush out the potential risks and benefits of dietary supplements,” says Tolliver.

Next, learn more about how to take supplements safely.