Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health and about any potential drug interactions or safety concerns.
You may be a devotee of certain supplements in pursuit of wellness. But if you’re also taking certain medications — maybe for a chronic health condition or even just for everyday aches and pains — it’s important to know that some combinations of supplements and drugs may spell trouble.
Read on to learn about seven supplement-and-medication combos to avoid. And remember: Talk to your healthcare practitioner about any supplement you may want to try to be sure that it doesn’t interact with medications you take.
1. Saint-John’s-Wort and Antidepressant Drugs
Practitioners of folk medicine have long turned to Saint-John’s-wort, a wild plant, as a treatment for mental health conditions. But according to the National Center for Complementary and Integrative Health (NCCIH), mixing Saint-John’s-wort with certain prescription antidepressants can lead to a dramatic and potentially life-threatening increase in serotonin, a chemical produced by nerve cells.
Symptoms can start within minutes and include rapid heartbeat, agitation, high blood pressure, and hallucinations.
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What’s more, Saint-John’s-wort may reduce the efficacy of many prescription drugs, including:
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- Contraceptive pills
- Digoxin, a drug used to treat various heart conditions
- Oxycodone, an opioid pain medication
- Cyclosporine, an immunosuppressant used to treat organ rejection post-transplant
- Certain cancer medications, including irinotecan
- Some HIV medications, including indinavir
- Warfarin, a blood thinner
“Saint-John’s-wort may also interfere with several drugs that are used prior to and during surgery, so make sure you tell your surgeon or anesthesiologist that you are taking this supplement,” says Jodie Pepin, PharmD, the clinical pharmacy program director of Harbor Health and a clinical assistant professor of pharmacy at the University of Texas at Austin. “They will likely instruct you to stop taking it five to seven days prior to your operation.”
2. Goldenseal and Metformin
The plant goldenseal in supplement form is marketed as a remedy for the common cold, respiratory tract infections, allergies, and upset stomach. But current scientific evidence doesn’t support these benefits.
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The major drug interaction to be concerned about with goldenseal is the diabetes medication metformin, Dr. Pepin says. A study published in 2025 found that goldenseal can reduce the efficacy of metformin by approximately 25 percent.
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3. Vitamin D and Blood Pressure Medications
“Generally speaking, most people need to supplement their vitamin D, and their blood levels should be monitored closely to optimal target levels,” says Lara Zakaria, PharmD, a registered pharmacist and certified nutrition specialist based in New York. “It’s uncommon that we tell patients not to use vitamin D because of medications. But that said, there are some considerations.”
The most significant interactions, she says, are with certain blood pressure medications, including verapamil, diltiazem, and thiazide diuretics.
Taking vitamin D with these drugs may reduce the effectiveness of the medication or increase the risk of hypercalcemia, a condition in which calcium levels in the blood are higher than normal. This can lead to kidney stones, weakened bones, and unpleasant symptoms like constipation, nausea, and vomiting.
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4. Omega-3 and Blood Thinners
Omega-3 fatty acids from foods like salmon and flaxseed have been linked with a number of health benefits, with some research suggesting that omega-3s may promote heart health.
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But research on the heart-healthy benefits of omega-3 supplements (also known as fish oil) has had mixed results, with some studies finding that the pills boost cardiovascular health and others that they have no impact.
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As far as drug interactions, omega-3 supplements can interact with medications that affect blood clotting, such as blood thinners (anticoagulants) or nonsteroidal anti-inflammatory drugs (NSAIDS), making it take longer for cuts to stop bleeding.
Anyone prepping for surgery should talk to their healthcare provider about discontinuing their supplement use prior to the procedure, Dr. Zakaria advises.
5. Vitamin C and Kidney Medications
Vitamin C is essential for building blood vessels, cartilage, and muscles. Most people get adequate amounts in their diet, but some may need supplementation if they’re prone to deficiency.
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While vitamin C supplementation is considered generally safe, there are a few potential interactions to be aware of. First, supplements may increase the absorption of aluminum from medications like phosphate binders, which help remove phosphate from the blood. This is often a treatment for people with kidney disease, so people taking this medication may want to avoid vitamin C supplements.
Vitamin C supplements may also interact with chemotherapy drugs, statins, niacin, protease inhibitors, warfarin, and estrogen medications.
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6. Turmeric and Over-the-Counter Pain Medicine
Research suggests that the spice turmeric, specifically its active compound curcumin, may help reduce inflammation and ease symptoms of conditions like anxiety, arthritis, degenerative eye disease, metabolic syndrome, and muscle soreness.
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But you’ll want to skip turmeric or curcumin capsules if you’re also using over-the-counter pain medications like aspirin, ibuprofen, and acetaminophen, as the supplement makes these drugs less effective. Turmeric may also reduce the effect of other medications, including certain types of chemotherapy drugs and indomethacin (a drug used to treat symptoms of arthritis), and may increase the risk of bleeding if taken with anticoagulants.
7. Kava and Anti-Anxiety Medications
Kava is a plant that has been used for thousands of years by Pacific Islanders as a medicine, ceremonial beverage, and relaxation aid. Today marketers tout kava supplements as a way to reduce anxiety and promote sleep. While some studies suggest this may be true, kava has been linked to serious incidences of liver injury, although the cause and frequency are still unclear.
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Kava can increase the effects of any medications that depress the central nervous system, Zakaria says. These include alcohol, opioid pain medication, and anti-anxiety medications like benzodiazepines.
It’s also worth noting that there’s no evidence showing the plant is safe for children, so parents should take heed. People who are pregnant or breastfeeding should not use kava, and anyone who wishes to try this supplement should do so only under the guidance of their healthcare provider.
The Takeaway
- Some supplements can be beneficial, but they aren’t regulated in the same way that over-the-counter medications are.
- Supplements can interact with prescription drugs or are dangerous when used alongside certain ailments.
- Saint-John’s-wort, goldenseal, vitamin D, omega-3, vitamin C, turmeric, and kava can pose risks when taken with certain medications, so always consult a healthcare practitioner before trying.
