Melatonin doses can vary from what’s on the label. Here’s how much.

Food and Drug Administration researchers have identified dozens of melatonin supplements with doses well above or below the amount listed on the label.

They analyzed 110 melatonin supplements purchased in 2023, focusing on ones marketed for children. Their study was first published in a peer-reviewed journal in October, but did not identify any of the products. The FDA’s study is the largest of melatonin-containing products in the United States, the researchers noted in a peer-reviewed article on the results.

The Washington Post filed a Freedom of Information Act request in November to obtain the names of the supplements tested, the results and any memo or report regarding the study.

Among the supplements tested, researchers found that three products from Zarbee’s, Robitussin, and Creekside Natural Therapeutics varied the most from the melatonin declared, according to the documents from the FOIA request. Three other brands, WellYeah, Calmable, and Nextdia, sold products that contained zero or close to zero detectable melatonin per serving, the documents show.

Some pediatric sleep medicine specialists said melatonin should be treated like a prescribed medicine, not a supplement. They also advised that children should be given the smallest effective dose, starting at half a milligram, after parents have tried other ways to help them sleep.

“This is not a vitamin,” said Paul Gringras, a professor of sleep medicine at King’s College in London and the president of the International Pediatric Sleep Association, a group that supports research on pediatric sleep medicine. “It is the messenger that transmits a signal to keep our clock in time to virtually every organ in the body.”

Tyish Hall Brown, the director of behavioral sleep medicine at Children’s National Hospital in D.C., said reports of the variability in melatonin supplements are “disconcerting.” But the dose in a serving is often still within what she considers an acceptable range (0.5 mg to 5 mg per serving) for a child or teenager, she said.

“We just have to be mindful of this inconsistency, and then monitor how they’re reacting to the supplement that they’re taking,” Hall Brown said. “We should use the lowest dose that produces the desired effect.”

Jeff Ventura, a spokesperson for the Council for Responsible Nutrition, a trade association for the supplement industry, said in an email that consumers — especially parents — should “have access to products that are accurately labeled and responsibly manufactured.” Ventura also wrote that the findings “reinforce the need for [the FDA] to take enforcement action against those companies that fail to meet these basic obligations.”

To measure the ingredients, the FDA researchers compiled a list of 199 melatonin supplements sold in the United States. An FDA spokesperson said in an email that “to mimic product searches of an average consumer, product selection was done through third-party online vendors using targeted keyword searches (e.g., ‘Melatonin+Child’).” The researchers froze and pulverized supplements to measure the melatonin.

The FDA examined specific brands and dosages of products, providing documentation of the exact product tested.

An FDA spokesperson did not respond to questions regarding the data provided or the researchers’ conclusions in the study.

The FDA spokesperson didn’t say whether the agency has contacted companies regarding the test results but said in an email that the study’s findings “are being taken into consideration” as the agency evaluates the safety of melatonin supplements.

Pieter Cohen, an associate professor of medicine at Harvard Medical School, who is a co-author of a 2023 letter in JAMA on melatonin supplements, said that his research and the FDA’s study only provide a “snapshot” regarding the melatonin in off-the-shelf supplements and that people shouldn’t use the results to decide what brands to avoid buying. Cohen and other physicians recommend people search for melatonin supplements that are third-party-tested by U.S. Pharmacopeia (USP).

A spokesperson for Kenvue, the maker of Zarbee’s, said Zarbee’s Sleep with Melatonin “is an adult product” that has been discontinued “at most major retailers but is still available online.”

Sam Osborne, a managing partner for Creekside Natural Therapeutics, whose product had six times the amount of melatonin on the label, said in an email that the FDA’s results “were both a surprise and a disappointment to us.”

“We have removed the fruit chews from the market and discontinued our business with the contract manufacturer who made those products for us,” Osborne said.

A spokesperson for Haleon, the company that owns Robitussin, said the Robitussin Naturals product line mentioned in the study, which had four times the amount of melatonin on the label, has been discontinued.

A spokesperson for Kenvue said in a statement that “the FDA permits the inclusion of some amount of overage to ensure that the product contains at least 100% of the ingredient quantity listed on the label throughout its shelf life.”

Patti Zettler, a professor of law at Ohio State University, said in an email that the FDA “has recognized” some supplement companies design products to have an additional amount of an ingredient “so that the product has at least 100% of the claimed amount of the ingredient throughout its shelf life.”

“But companies also have an obligation under the law to ensure that their products meet safety standards,” Zettler said.

Neal Fortin, a professor and the director of the Institute for Food Laws & Regulations at Michigan State University, said companies “should know their product” and the degree to which the active ingredients in dietary supplement degrade over time.

“If they’re relying on putting a whole bunch in extra just so you make sure you get what you have, that’s bad manufacturing practices,” Fortin said. “That’s not allowed.”

Supplement companies could either reformulate their product for more stability or shorten its shelf life so they don’t have overages, Fortin said.

“Some of these things can be dangerous if they’re in large amounts — or larger than expected,” he said.

People associated with the companies behind the brands Calmable, Doctor’s Finest and WellYeah did not respond to requests for comments. A representative for Nextdia declined to comment.

Mike Poll, a senior purchaser for Nutrabulk, one of the three brands with the correct dosage, said in an email “we are pleased but not surprised” by the results of the FDA study.

Melatonin is a hormone our brain releases at night to regulate the body’s sleep-wake cycle, or circadian rhythm.

Melatonin supplements help a person transition to bedtime, but it is not a sedative, Hall Brown said.

When someone is having a hard time falling asleep at an earlier bedtime, melatonin supplements can help them adjust their circadian rhythm, she said. For example, people often take melatonin to manage jet lag.

Melatonin is considered a dietary supplement in the United States. The FDA doesn’t regulate dietary supplements as rigorously as it does prescription medications, or test them for safety and efficacy.

In recent years, more adults have started taking melatonin supplements before bedtime, and some parents give them to children, although the practice isn’t universally supported.

Melatonin supplements are generally considered safe for children older than 2 years old to take in small doses for short periods of time — days, not weeks or months, states the International Pediatric Sleep Association.

But one survey showed that parents of school-age children were giving melatonin to their kids for 18 months, on average.

Studies have found that melatonin can help children with autism or attention-deficit/hyperactivity disorder fall asleep faster and sleep longer. But there’s limited evidence supporting use for other children, and less is known regarding long-term use of the supplements.

Some physicians are concerned melatonin supplements could affect children’s growth and development.

“We’re selling an active hormone, we’re giving it to our children, and we have no idea how much we’re giving them,” Cohen said.

“We don’t know the long-term effects — at all — of this product,” said Cora Collette Breuner, a professor of pediatrics at the University of Washington School of Medicine and member of the American Academy of Pediatrics.

The American Academy of Pediatrics states melatonin “should only be used” in consultation with a pediatrician and after establishing other healthy sleep habits.

Muhammad Rishi, an associate professor of medicine at Indiana University School of Medicine and spokesperson for the American Academy of Sleep Medicine, said that “the public needs to understand that melatonin is not a dietary supplement.”

Other physicians said melatonin can help some children.

“Sometimes the benefits of helping a child sleep outweigh the minor risks, as long as you’re treating it like a drug,” said Beth Malow, a professor of neurology and pediatrics at Vanderbilt University Medical Center who has conducted research on melatonin for children with autism. “Using behavioral interventions is best, but it’s not always possible.”

Hall Brown said she works with parents to implement behavioral techniques first, such as having a consistent bedtime. Then she’ll recommend melatonin as “a second line of defense.”

The side effects of melatonin supplements are typically mild but they are associated with vivid dreams, bed-wetting, grogginess, headaches, and dizziness. All the physicians interviewed advised parents to consult a healthcare provider before giving a child melatonin.

Children tend to fall asleep faster if they have a consistent bedtime and an evening wind-down routine.

You can also create a “cave-like” environment for the child that’s cool and dark, Gringras said. Limit light and light-emitting devices such as tablets or phones because the light can suppress the brain’s release of melatonin. The American Academy of Pediatrics recommends children avoid screens for at least one hour before bedtime.

Parents who do try melatonin should employ a “two-pronged approach,” pairing the drug with a bedtime routine, because the melatonin won’t work forever, Gringras said.

“When it stops working,” he said, “you want the young person to have learned good behavioral habits that will last for the rest of their life.”

Aaron Schaffer contributed to this report.