6 Supplements That Don’t Always Mix With Prescription Drugs

2. CoQ10

Coenzyme Q10 (CoQ10) is an antioxidant produced by our bodies to promote cell growth and maintenance; the levels of it in our body can decrease as we age.

In supplement form, it’s taken by way of capsules, tablets and syrups for numerous conditions, including heart disease, diabetes and migraine. But CoQ10 can also interfere with the ability of blood thinners to do their job, which is to prevent blood clots from forming. As a result, “people could have a breakthrough blood clot,” Shane-McWhorter says.

3. Turmeric

The ancient spice has been shown to have many health benefits, from improving memory to lowering inflammation and even decreasing the risk of heart disease. It also has anticoagulant effects, which means you don’t want to mix turmeric supplements with a blood thinner or even, possibly, aspirin, due to the risk of internal bleeding, Shane-McWhorter says.

Ginkgo biloba (an herb) and vitamin E are two other dietary supplements that can thin the blood, according to the Food and Drug Administration. So taking them with an anticoagulant can augment the effect. 

Cooking with turmeric? It’s still fine to use in the kitchen, Shane-McWhorter says. “When products are used as foods, we don’t think it’s that much of an issue at all,” she adds.

4. Probiotics

Full of beneficial bacteria, probiotics are often taken to aid digestion and improve gut health. But don’t take one within two hours of taking an antibiotic, or you could reduce the effectiveness of the prescription medication, Shane-McWhorter says.

5. Vitamin C

Vitamin C occurs naturally in citrus fruits, strawberries, broccoli and tomatoes, among other foods. It’s also consumed as a supplement for a myriad of reasons, ranging from warding off the common cold to preventing cancer.

But high-dose vitamin C supplements may reduce the effectiveness of some types of cancer chemotherapy, says Courtney Rhodes, a spokeswoman for the FDA. It can also interfere with niacin and statins and affect estrogen levels, according to Mayo Clinic.

6. Milk thistle

A flowering plant related to daisies, milk thistle is taken as a supplement to promote liver and heart health. It may also lower blood sugar, which could be a concern for someone who’s on diabetes medication. When combined with insulin, it can be “like taking a little bit too much” glucose-lowering medication, Shane-McWhorter says.

Bottom line: Talk to your doctor

Ideally, to head off trouble, patients would be talking to their doctors about the supplements they are taking. But these conversations don’t happen as often as they should, says Derjung Mimi Tarn, M.D., a professor of family medicine at University of California, Los Angeles.

A study led by Tarn and her colleagues in 2015 found that fewer than 50 percent of patients disclose the use of dietary supplements, and even among those who do, only about one-third of the supplements taken are mentioned to doctors.

One reason for the disconnect: Patients may not realize the over-the-counter herbs or extra vitamins they’re working into their daily pile of pills count as anything that needs to be discussed with a doctor, so they leave them off the list when their provider asks, Shane-McWhorter explains. It’s also not uncommon for consumers to confuse “natural” with “safe” and fail to fully recognize the potency of some of these products.

To help avoid any health hazards that can arise from mixing supplements and medications, it’s important to ask your doctor about possible adverse reactions before starting any new medication or supplement, Tarn says. “Greater awareness of the importance of discussing supplement use is needed in both providers and patients,” she adds.

The FDA suggests bringing a list of everything you take — over-the-counter medicines (pain pills, allergy relief, etc.), dietary supplements and prescription drugs — with you to your next routine appointment to make sure your information is up to date. And be sure to keep track of the dosages and how many times a day you take them.

Also, if you’re planning a surgery, don’t be surprised if your doctor asks you to stop taking dietary supplements two or three weeks before the procedure to avoid changes in heart rate, blood pressure or bleeding risk.

Interested in learning more? The National Institutes of Health has a database where you can search for a supplement and find links to verified sources with information about the product and its interactions. And Herbs at a Glance is an alphabetical listing of herbs and botanicals, with information on their uses and safety concerns, from the National Center for Complementary and Integrative Health, a division of the NIH.

For those willing to pay, Shane-McWhorter recommends the Natural Medicines database, where subscribers can use the interaction checker and the effectiveness checker to learn more about particular supplements.