There has been a fivefold increase in U.S. adults taking melatonin supplements for sleep, according to a study co-authored by Dr. Naima Covassin, a researcher in Mayo Clinic's Cardiology Lab. Melatonin is a hormone in the body that plays a role in your natural sleep-wake cycle. And it's available as a supplement that around 6 million adults in the U.S are taking to help manage their sleep. But are they using it correctly?

"Most of the times, melatonin is actually misused because it's used as a general sleep aid and to help with insomnia," says Dr. Covassin.

"When you look at the actual clinical evidence, in terms of clinical efficacy of the use of melatonin supplements against insomnia, there is actually relatively weak evidence."

Dr. Covassin says melatonin is not a sleep promoter. It's a circadian rhythm regulator that can help "reset our clocks" when sleep is difficult due to circadian disruption from things like shift work, jet lag or disorders that interfere with the time of sleep.

Not only are more people using melatonin supplements, they're taking higher doses than the typically recommended maximum dose of 5 or fewer milligrams.

"Higher doses are not necessarily more effective, and actually can be counterproductive because they can have opposite effects," she says. "They may end up making you sleepy during the day, when you don't want to be sleeping, and also increase risk of adverse effects, as well."

Serious side effects include worsening of seizures; changes in heart rate and blood pressure; decrease in glucose tolerance; and possible drug interactions for people taking seizure disorder medications, antidepressants or blood thinners.

"Because something is marketed as 'natural' or a product is sold over the counter doesn't mean it's harmless."

That is why Dr. Covassin's best recommendation is to talk with your provider.

"Discuss with their physician while they're taking it, or if they are considering taking it, whether it's actually the best course of action for them," says Dr. Covassin.