Melatonin gummies are often mislabeled, study finds. Too much of the sleep aid can lead to unpleasant side effects — especially in kids.

• A new analysis found 22 out of 25 melatonin gummies mislabeled the amount of melatonin contained in supplements.
• One melatonin gummy contained no melatonin at all, while another had 347% of the amount listed.

Melatonin gummies might contain more melatonin than the bottle they're in says they do.

Researchers at Harvard and Ole Miss tested 25 types of melatonin gummies currently on the market and found 22 of them did not contain the amount listed on the label. Actual melatonin doses ranged from 74% to 347% of the amount listed, and one sample didn't contain any melatonin at all.

"Given these findings, clinicians should advise parents that pediatric use of melatonin gummies may result in ingestion of unpredictable quantities of melatonin," the study's authors wrote in a letter published in the Journal of the American Medical Association.

The report comes a year after the Centers for Disease Control and Prevention reported that calls to poison control centers involving children who took too many melatonin supplements increased by 530% in the last decade, though the vast majority of cases didn't result in long-term harm.

But the side effects from ingesting more than the recommended dose aren't pleasant. Children might experience vomiting and diarrhea, while adults can get dizzy or irritable.

This isn't the first analysis showing melatonin supplements mislabel the amount of the synthetic hormone in them. In 2017, a study published in the Journal of Clinical Sleep Medicine found 71% of the 31 supplement brands analyzed contained anywhere between 83% less to 478% more melatonin than they claimed on the bottle, and the amount of melatonin within different pills in the same jar varied by 465%.

Variations in dose can occur because the makers of melatonin supplements, like those of all dietary and herbal supplements, aren't subject to strict regulation by the Food and Drug Administration.

Melatonin supplements aren't the best fix for poor sleep

Melatonin is a sleep hormone produced in the brain that builds up throughout the day and is released right before bed. Melatonin supplements increase the amount of hormone in the body and can cause sleepiness, sleep scientists previously told Insider, but they aren't effective beyond a 10 milligram dose.

Melatonin use has been creeping up for the past several decades. Supplement sales skyrocketed after the onset of COVID-19, when many Americans reported trouble sleeping due to increased stress and anxiety. And a recent survey of 3,000 parents found 10 percent of them give children under 18 melatonin.

Melatonin supplements don't solve the underlying reason for why people might have insomnia, Dr. Raj Dasgupta, a board-certified sleep and internal medicine doctor and spokesperson for the American Academy of Sleep Medicine (AASM), told Insider. Dasgupta said improving exercise and diet, or seeking cognitive behavioral therapy, are more cost-effective, long-term solutions to improve sleep.

"Taking supplements beyond the recommended daily allowance hasn't shown to be beneficial in other ways, and I always say that, because times are tough and money is hard to come by," Dasgupta said.