Melatonin has become a popular sleep aid supplement, but Self reports that it’s probably not your best bet if you’re having trouble sleeping.

Research has found that the right dosage for melatonin as a sleep aid is 0.3 milligrams, but many melatonin supplements are marketed in 3 milligram tablets. That’s 10 times the amount your body needs, and that’s assuming you’re only taking one pill or capsule. What’s more, because melatonin pills are classified as a dietary supplement, they’re pretty unregulated by the FDA. As a result, the supplement may say they contain a certain amount of melatonin, while the pills actually have a different amount.

That’s concerning, Indira Gurubhagavatula, M.D., MPH, an associate professor of sleep medicine at the University of Pennsylvania’s Perelman School of Medicine, tells SELF. “What is the quantity of the drug that you’re actually getting and how much is in each of those pills?” she says. “Since it isn’t regulated, it could be any amount. People have tested the tablets and found that the amounts are all over the place.” (It’s also possible for the supplement’s ingredients list to say one thing, while the actual pills contain something else entirely or additional ingredients you may not be aware of, Gurubhagavatula says.)