How Much Melatonin Is Too Much? Your Supplement Label May Not Be Telling the Truth

If you take melatonin to wind down at night, you could be getting a much larger dose than expected. In a research letter published last week, researchers found that 22 out of 25 melatonin gummies contained different amounts of melatonin than what was listed on the label.

The actual amount of melatonin in each product ranged from 74% to 347% of the labeled dosage, and all but three of the products were over the labeled dosage.

Melatonin is classified by the Food and Drug Administration as a dietary supplement, which means it’s not regulated as carefully as over-the-counter and prescription drugs are.

The researchers only tested one sample from each brand and the quantity of melatonin may vary from batch to batch, even within a single brand. Still, the discrepancies highlight how little consumers may know about their dietary supplements, said John Saito, MD, FAAP, FCCP, a pediatric pulmonologist and sleep medicine specialist.

“In this case of melatonin, as this study highlights, the dosage and the variability are like the wild wild West,” Saito told Verywell. “We say ‘dosage’ because it’s not a dietary supplement, it’s a medication. The uncertainty comes when you’re asking for the appropriate dosage for a supplement that has no consistency.”

This is the first U.S. study to measure the amount of melatonin in over-the-counter melatonin products, according to the study authors. However, a 2017 study of 16 Canadian melatonin brands found similar results. The actual doses in those products ranged from 17% to 478% of the labeled quantity.

Should You Worry About Taking Too Much Melatonin?

The labels on the 25 melatonin supplements contained various health claims, such as sleep support, circadian rhythm support, heartburn relief, resting and restoring muscles, and immune support.  

Melatonin is a naturally occurring hormone that helps regulate sleep and circadian rhythms. When it gets darker, the body releases melatonin to signal to the brain that it’s time to sleep. Overloading the body with melatonin can cause someone to wake up feeling dazed and confused.

“Anytime you’re taking a medication that is supposed to help with sleep, it can be sedating. If you take too much of it, you can have a hangover effect the next day, and it can affect your ability to think,” S. Justin Thomas, PhD, FSBSM, assistant professor and director of the behavioral sleep medicine program at the University of Alabama at Birmingham, told Verywell.

Some people report having more intense nightmares and experiencing gastrointestinal side effects, like nausea. Melatonin can also lower blood pressure, which can cause hypotension. That could be dangerous for older adults as it puts them at greater risk for falls, Thomas said.

Melatonin gummy may also be particularly appealing to kids because of its candy-like taste and appearance, and they may not stop eating after having just one, Thomas said.

Between 2012 and 2021, the U.S. Poison Control Centers saw a 530% increase in calls related to melatonin ingestion. In those 10 years, nearly 28,000 emergency room and clinic visits, 287 intensive care unit admissions, and two deaths were associated with melatonin.

The amount of melatonin that is needed to regulate the circadian rhythm is between 0.1 and 0.3 milligrams. But most melatonin supplements say they contain at least 3 mg, far more than what’s necessary.

“And then finding out that instead of getting a milligram you’re getting 13 or more—that’s really scary because that’s an excessive amount of melatonin,” Thomas said.

Melatonin is processed in the liver. Over time, an excess of melatonin could cause liver damage, according to Saito.

“We don’t have any long-term studies in terms of chronic high exposure to melatonin, but I would only guess if you are challenging your liver’s ability to detoxify, that over time you just accelerate the wear and tear and ultimately, the breakdown of organ system,” Saito said.

People who are on medications that are metabolized in the liver may see an increased risk of toxicity from those drugs if the liver is also asked to process excess melatonin.

The harm could be especially pronounced in children because their bodies are still developing, Saito said. Chronic over-exposure to melatonin could cause their bodies to decrease their natural melatonin production. Over time, their bodies may become dependent on the supplement for regular sleep.

“For kids, I recommend starting at two to three milligrams and kind of seeing their response to that. I wouldn’t go up more than that,” Saito said.

How Can You Check If Your Melatonin Supplements Are Safe?

Supplements can sometimes contain unsavory contaminants, like pesticides, heavy metals, steroids, and bacteria. Just because a supplement is sold in a pharmacy doesn’t mean that it’s been well tested.

Experiencing unusual gastrointestinal side effects, worse dreams, or more frequent headaches could be a sign to reduce one’s melatonin dose, Thomas said.

Taking melatonin at the right time is also key to effectively regulating sleep, Thomas said. People who are looking to treat circadian rhythm disorders and other sleep problems should consult with a primary care or sleep medicine physician for help with dosing and choosing the best supplement option.

There are some third-party groups that test common supplements to ensure they contain the ingredients on the label and that they’re not contaminated those that are not. These include ConsumerLab.com, NSF International, and U.S. Pharmacopeia.

“You have to stay alert as to what you’re taking and not assume that what’s on the label is what you’re getting. If you’re taking two or three milligrams of melatonin and you’re knocked out for a long period of time, you’re probably not getting the dose that’s on the label,” Saito said. “In general, it’s a mild sleep aid. If it’s acting like a narcotic, you know that dose is not right.”