When it comes to supplements, “natural” doesn’t always mean safe—especially if you’re already taking prescription medication. Many popular herbs and vitamins can interfere with how drugs work in the body, sometimes leading to serious or even dangerous side effects. Janelle Bober, MS, RDN from Dietitian Live, is shedding light on three common supplements — St. John’s Wort, Ginkgo Biloba, and Ginseng — that may do more harm than good when mixed with certain medications. Here’s what you need to know before adding them to your daily routine.
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1. St. John’s Wort and Antidepressants
While St. John’s Wort is often taken to ease mild depression, pairing it with prescription antidepressants can be risky rather than helpful.
"It basically interacts with one of our CYP metabolizing systems in our liver and it creates P glycoprotein, and this lowers blood levels of medications, namely antidepressants," says Bober. In addition to reducing a drug’s effectiveness, this interaction can raise the risk of serotonin syndrome — a potentially dangerous condition — much like ginseng.
"This is one of the most studied and researched combinations," she emphasizes. The key takeaway: avoid mixing St. John’s Wort with antidepressants, and choose safer alternatives such as herbal teas or magnesium for mood support.
2. Ginkgo Biloba and Blood Thinners
Ginkgo Biloba is often praised for its brain-boosting effects, but if you take blood thinners like aspirin, warfarin, or clopidogrel, it could pose serious health risks.
"Ginkgo actually impairs platelet aggregation," says Bober. "When combined with blood thinners, it significantly increases your bleeding risk." This can be particularly dangerous for those with bleeding disorders or anyone preparing for surgery.
To avoid complications, Bober suggests reaching for alternatives like turmeric or ginger, which may offer similar cognitive or circulatory benefits without the same level of danger.
3. Ginseng and Blood Thinners
The potential side effects of ginseng go beyond antidepressant interactions—it can also interfere with blood thinners such as warfarin or other anticoagulant and antiplatelet drugs.
"What happens is that it actually decreases the effect of these medications, and it can decrease our ability to thin our blood," Bober explains. "If we have less coagulation, it can increase the risk of blood clots and actually lead to possible stroke."
For anyone prescribed a blood thinner, it’s essential to speak with a healthcare professional before adding ginseng to your supplement routine, and to keep a close watch on your medication’s effectiveness.
