Supplement and Medication Interactions to Know
Supplements can change how medications work. Here are the interactions to know.
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1. Common Interactions
| Supplement | Medication Type | Concern |
|---|---|---|
| St. John's wort | Antidepressants, birth control, many others | Reduces effectiveness or causes serotonin syndrome |
| Vitamin K | Warfarin | Reduces anticoagulant effect |
| Fish oil, garlic, ginkgo, turmeric | Blood thinners | Increased bleeding risk |
| Calcium, iron, magnesium | Thyroid medication, some antibiotics | Reduced absorption |
| Potassium | ACE inhibitors, some diuretics | High potassium |
| Stimulant pre-workouts, yohimbine | Blood pressure medication | Raised blood pressure |
| Berberine | Diabetes medications | Low blood sugar |
| Melatonin | Sedatives | Excess sedation |
2. How to Stay Safe
- Tell your doctor and pharmacist about every supplement
- Bring your supplement bottles to appointments
- Introduce one new supplement at a time
- Stop and seek advice if you notice new symptoms
3. How Interactions Happen
Supplements can interact with medications in several ways: by changing how the liver breaks down drugs, by affecting absorption in the gut, by adding to or opposing a medication's effects, or by changing blood levels of minerals like potassium. These interactions can make medications less effective or increase side effects.
Herbal supplements are especially likely to interact because they contain many active compounds.
4. High-Risk Groups
Older adults taking multiple medications, people with chronic conditions like heart disease or diabetes, pregnant women and people undergoing surgery or cancer treatment are at higher risk of supplement-drug interactions. These groups should review every supplement with a healthcare provider.
5. Before Surgery
Some supplements, such as fish oil, garlic, ginkgo and vitamin E, may increase bleeding risk. Tell your surgeon about all supplements and follow instructions about stopping them before procedures.
6. Our Recommendation
Keep an up-to-date list of medications and supplements and share it at every medical visit.
7. Common Supplements With Interaction Risks
St. John's wort, ginkgo, garlic supplements, fish oil, vitamin K, grapefruit extracts, berberine, licorice root, potassium and high-dose vitamin E are among the supplements most often involved in interactions. If you take any of these, review your medications with a pharmacist. Even common vitamins and minerals can interact with specific drugs.
Pharmacists are an excellent, often free resource for checking interactions.
8. Using Interaction Checkers
Online interaction checkers can flag potential problems, but they aren't a substitute for professional advice. Use them as a starting point for a conversation with your pharmacist or doctor.
9. How Interactions Happen
Supplements can interact with medications by changing how drugs are absorbed, metabolized or eliminated, or by adding to or opposing a drug's effects. For example, St. John's wort speeds up metabolism of many medications, reducing their effectiveness, while fish oil and ginkgo may increase bleeding risk with blood thinners.
Always tell every doctor and pharmacist about all supplements you take.
Final Thoughts
Supplement drug interactions are common and sometimes serious, especially with blood thinners, antidepressants, thyroid and blood pressure medications. Always share your full supplement list with your healthcare team. This article is for general information only and isn't medical advice. Talk to a doctor or registered dietitian before starting a supplement, especially if you're pregnant or nursing, take medication or have a health condition.
Frequently Asked Questions
- Can supplements affect blood pressure medication?
- Yes; stimulants, licorice and potassium are common concerns.
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