- Some supplements can interact with certain medications and reduce their effectiveness.
- Top offenders include calcium, magnesium, iron, fiber, activated charcoal and vitamins C and K.
- If you take supplements, talk to your health care provider to make sure they are safe for you.
If you’re looking to upgrade your health routine, you might be considering a supplement. Or maybe you’re even taking one now. While supplements are generally sold over the counter, that doesn’t mean they don’t have risks. And one to be on the lookout for is medication interactions, which can decrease the effectiveness of your meds.
For instance, some vitamin and mineral supplements can interfere with absorption of medications. Other supplements can bind with medications, preventing the drug from being utilized in the body, or they may be metabolized by the same or similar pathways as medications, explains naturopathic doctor Jacob Wolf, N.D., LAc, Dipl. OM. That can have a dangerous impact on your health.
Which supplements should be on your radar? To find out, we talked to the experts. Here are five supplements they say could be reducing your medication’s effectiveness.
1. Calcium, Magnesium and Iron
Minerals like calcium, magnesium and iron can bind with medications, especially levothyroxine, a drug used to treat hypothyroidism, says Wolf., This can impact how levothyroxine is utilized in the body, adversely affecting treatment, he says.
These minerals can also interact with antibiotics in the tetracycline and fluoroquinolone class, says pharmacist Amanda Corbett, Pharm.D., BCPS, FCCP, FAIHM. Taking these mineral supplements at the same time as antibiotics may reduce the bioavailability of the antibiotic, creating risks like bacterial resistance or ineffective treatment.
When you receive a new medication prescription, Corbett recommends checking with your pharmacist before taking any mineral supplements, including multivitamins or multimineral formulations. For antibiotics, be sure to ask whether you should make any temporary adjustments to your supplement routine. With levothyroxine, a good rule of thumb is to avoid taking these minerals within four hours of your medication. However, it’s a good idea to check with your health care provider to be sure.
2. Fiber
Fiber is an important nutrient for digestive regularity, healthy cholesterol levels, blood sugar management and more. You can find fiber in plant foods like fruits, vegetables, beans, lentils and whole grains. You can also get it from supplements. However, as good for you as fiber is, supplementing isn’t always a great idea, as large doses can impact the absorption of certain medications.
One of note is the diabetes medication metformin. Emerging research suggests that taking a fiber supplement with metformin may impair this medication’s ability to lower blood sugar. If you’re wondering about fiber from food, there’s no need to worry. Fiber-rich foods are a cornerstone of blood sugar management, even for those taking blood sugar–lowering medications, like metformin.
Fiber may also impair the effectiveness of other drugs, including digoxin (which treats certain heart conditions) and levothyroxine for hypothyroidism, Wolf points out., If you do choose to take a fiber supplement, Wolf recommends speaking with your health care provider about spacing out your fiber and medication doses.
3. Activated Charcoal
Activated charcoal is a form of carbon that is used in the emergency room to treat the ingestion of toxic drugs and poisons., It is also sold in supplements marketed to help you detox. While it may soak up toxic substances when used appropriately in a medical setting, at home, it can have detrimental effects. “Activated charcoal acts like a sponge and can bind to many medications. It is best to completely avoid activated charcoal if on any life-critical medication,” says Wolf.
4. Vitamin C
Vitamin C is an important antioxidant that protects cells from free radical damage and supports proper immune system function. However, if you are undergoing chemotherapy treatment for cancer, experts strongly caution against taking vitamin C supplements. “Vitamin C can lead to certain chemotherapies being less effective or ineffective in treating cancer,” says Corbett. Vitamin E, another antioxidant, can also interfere with chemotherapy’s effectiveness.
5. Vitamin K
Vitamin K is a fat-soluble vitamin that helps blood clot and shores up bone health. However, vitamin K can reduce the effectiveness of a blood-thinning medication called warfarin (Coumadin). That, in turn, can make blood more likely to clot, which can lead to a heart attack or stroke. If you are taking warfarin, you don’t necessarily need to avoid vitamin K, but it is critical to keep the amount you consume—from both foods and supplements—consistent to avoid clotting problems.
Tips to Take Supplements Safely
- Consult with your health care provider. Just because supplements are sold over-the-counter, that doesn’t mean they’re benign. Many supplements can interact with medications, and so it’s critical to connect with your prescribing health care provider to make sure that the supplements you’re taking play nice with your medications. Your pharmacist can also be a valuable resource, so speak with them as well.
- Choose quality supplements. Look for those that have been independently tested in a laboratory, recommends Corbett. “The testing should confirm the ingredients on the dietary supplement label are indeed the ingredients [in the product] and the product should have safe levels of heavy metals,” she says. Products should also be free of added medications, something that independent testing also looks for. Trusted independent testing organizations include ConsumerLab, NSF and U.S. Pharmacopeia (USP).
- Know how much to take. Supplement dosages are listed on the label, but they aren’t standardized. That means they can vary from product to product, and may far exceed safe levels. Instead of assuming the dose on the label is the right amount, it’s better to ask your health care provider about the dose that’s right for you.
Our Expert Take
Certain supplements can interact with medications you’re taking, potentially making them less effective. Some of the biggest troublemakers include calcium, magnesium, iron, fiber, activated charcoal, and vitamins C and K. But that’s just the short list. Before adding any supplement to your routine or starting a new medication, talk to your health care provider about possible interactions. They can tell you whether the supplement is safe for you, and, if so, how much to take and the best time of day to take it.
