The sleep aid melatonin could interfere with birth control pills, reports POPSUGAR.

Savita Ginde, MD, vice president of medical affairs at Stride Community Health Center and former chief medical officer of Planned Parenthood of the Rocky Mountains, explained that melatonin is naturally produced in the pineal gland, the same gland that regulates female hormone levels. “While there are no definitive studies, “one can propose that taking or adding external melatonin could impact natural cycles, whether it’s natural sleep cycles or natural hormonal cycles, such as those that impact ovulation and menstrual cycles and thus affect fertility,” Dr. Ginde told POPSUGAR.

Then there’s the matter of where and how the body metabolizes melatonin. Heather Bartos, MD, a board-certified ob-gyn, told POPSUGAR that melatonin is metabolized in the liver along with a number of other medications, including birth control pills. “By asking the liver to do double duty, it can lower the effectiveness of the birth control pill,” she explained. Dr. Bartos added that certain antibiotics, medications, and supplements can also interfere with the metabolization of birth control, including St. John’s wort, an over-the-counter supplement that’s commonly used to treat depression.