St. John's Wort Side Effects: What You Need to Know Before Taking It

When people look for natural ways to feel better, St. John's Wort, a herbal supplement used for mild depression and mood support. Also known as Hypericum perforatum, it's one of the most widely used herbal remedies in the U.S. and Europe—but what many don’t realize is that it doesn’t play nice with other medications. This isn’t just about mild stomach upset. St. John’s Wort can interfere with how your body processes prescription drugs, sometimes making them useless—or dangerously strong.

It affects antidepressants, medications like SSRIs and SNRIs used to treat depression and anxiety, by boosting serotonin levels too high. That can lead to serotonin syndrome, a real medical emergency with symptoms like confusion, rapid heart rate, and muscle stiffness. It also messes with birth control pills, hormonal contraceptives that rely on steady hormone levels to work. Women have gotten pregnant while taking St. John’s Wort, thinking they were protected. And it reduces the effectiveness of blood thinners, drugs like warfarin that prevent clots, increasing stroke and clotting risks. Even common drugs like statins, HIV meds, and transplant rejection drugs can become less effective—or more toxic—when mixed with it.

Side effects aren’t just about drug clashes. People report dry mouth, dizziness, stomach upset, and increased sensitivity to sunlight. Some get rashes or sunburns more easily than usual. It can also trigger mania in people with bipolar disorder, which is why doctors don’t recommend it without supervision. And here’s the kicker: because it’s sold as a supplement, it’s not held to the same safety standards as prescription drugs. The dose, purity, and strength can vary wildly between brands.

There’s no magic here. If you’re thinking about trying St. John’s Wort for low mood, anxiety, or sleep issues, talk to your pharmacist or doctor first. Don’t assume natural means safe. Many of the posts below show how easily herbal remedies like this can interfere with common treatments—from HIV meds to thyroid drugs to cholesterol pills. You’ll find real examples of what happens when people mix supplements with prescriptions, and how to spot the warning signs before it’s too late. This isn’t about scaring you off herbs. It’s about helping you make smart choices so you don’t end up in the ER because you didn’t know what was in that bottle.