"Just because something is natural doesn't make it safe, says pharmacologist Joe Graedon. Always check with your doctor before taking supplements—especially if you use medication, have surgery scheduled, or are over 65."

St. John's Wort and antidepressants are a bad combination. St. John's Wort and antidepressants can cause side effects like a buildup of serotonin. Instead of St. John's Wort, take omega-3 fatty acids to lift your mood.

Turmeric and blood thinners don't mix well. The combination of turmeric and blood thinners can increase the risk of bleeding. Replace turmeric with grape or pomegranate juice for arthritis relief.

Licorice shouldn't be combined with diuretics for high blood pressure. This combination of licorice and diuretics can lower your potassium levels. Switch the licorice for ginger tea, for settling your stomach.

Don't take feverfew and blood thinners. Combining feverfew and blood thinners can lead to slow clotting. Taking plenty of magnesium instead of feverfew can make migraines less likely.

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