Supplements are often seen as harmless boosters for better health — but when mixed with prescription medications, they can have surprising and sometimes serious effects. Here’s a look at some of the most common and risky combinations to avoid.
Iron or Calcium with Thyroid Medication
Minerals like calcium and iron can block the absorption of thyroid hormone replacements such as levothyroxine. To keep your medication effective, take supplements and thyroid meds at least four hours apart.
St. John’s Wort and Antidepressants
This popular herbal mood booster can dangerously interfere with prescription antidepressants and birth control pills. It may lower drug levels or cause unwanted side effects like anxiety or restlessness.
Vitamin K and Blood Thinners
Vitamin K can weaken the effects of anticoagulant drugs such as warfarin, increasing the risk of blood clots. If you’re taking blood thinners, don’t adjust your vitamin K intake without medical guidance.
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Licorice Root and Diuretics
Licorice root can raise blood pressure and deplete potassium, making diuretics less effective or even harmful. People on blood pressure or water pills should avoid this combination entirely.
Ginkgo Biloba and Anticoagulants
When combined with medications like warfarin or aspirin, ginkgo can increase bleeding risk. Even small doses may amplify bruising or nosebleeds, so it’s best avoided if you’re taking blood thinners.
Vitamin B6 and Levodopa
Large doses of vitamin B6 can interfere with levodopa, a key Parkinson’s medication. However, forms containing carbidopa help offset this problem — so talk with your provider before adding supplements.
Vitamin C and Antacids
Antacids containing aluminum — like Maalox or Gaviscon — can react with vitamin C, leading to high aluminum levels in the body. Space your doses by at least two hours to stay safe.
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Goldenseal and Anticoagulants
Goldenseal, a popular herbal remedy for infections, can thin the blood too much when used with anticoagulants. The mix may cause internal bleeding or easy bruising, making it a risky pairing.
Vitamin E and Blood Thinners
Vitamin E may seem harmless, but in high doses it can increase bleeding risk when taken alongside anticoagulant or antiplatelet medications. Always get approval before combining the two.
Timing matters
Some medications — such as osteoporosis and thyroid drugs — work best when taken on an empty stomach and spaced well apart from supplements. A gap of at least two to four hours is often recommended.
Talk to your pharmacist
Your pharmacist can help you spot dangerous supplement and drug interactions before they happen. Always share a complete list of what you take, including vitamins and herbal remedies, to ensure every combination is safe.
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This article is based on information from Verywell Health and MedlinePlus
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