TV doctor Dr Amir Khan has issued an urgent warning for anyone taking warfarin, tetracyclines, ciprofloxacin, and certain statins, as some supplements can interfere with their effectiveness. Speaking on Instagram, the This Morning and Lorraine regular emphasised the importance of checking with a doctor before combining supplements with prescription medications.
Common Supplements and Their Risks
Dr Khan highlighted several popular supplements that can cause problems. St. John's wort, often used for low mood, is a major culprit. “It can interfere with anti-depressants, the contraceptive pill, blood thinners, and even medication used after organ transplants,” he explained. “It changes how your liver processes drugs.”
Turmeric or curcumin supplements, widely taken for inflammation and joint pain, pose a risk for those on blood thinners like warfarin. “There’s concern about increased bleeding risk,” Dr Khan said. Magnesium supplements can also affect absorption of certain antibiotics and thyroid medication. “Timing can matter,” he advised.
Specific Interactions
For thyroid medication like levothyroxine, experts recommend a four-hour gap before taking magnesium. Blue Horizon blood tests stated: “To ensure your medication works correctly, leave at least four hours between levothyroxine and magnesium supplements.” For antibiotics, magnesium can reduce absorption of tetracyclines (e.g., doxycycline) and fluoroquinolones (e.g., ciprofloxacin, levofloxacin). Experts advise taking these antibiotics at least two hours before or four to six hours after magnesium.
Bisphosphonates used for osteoporosis, such as alendronate and ibandronate, can also be affected by magnesium, which interferes with absorption and neutralises stomach acid. Calcium supplements similarly reduce absorption of levothyroxine and some antibiotics. Vitamin K, important for bone health, can interfere with warfarin by affecting bleeding and clotting risks.
Other Interactions
Even grapefruit juice, though not a supplement, can interact with some statins and other medications by affecting drug breakdown. Dr Khan concluded: “This doesn’t mean supplements are bad. Some are genuinely helpful. But if you’re taking regular medication, tell your doctor which supplements you take. Sometimes the interaction isn’t between two medications but between a medicine and something you thought was harmless.”
