Melatonin is sold as a dietary supplement in the United States, but it’s actually a hormone your brain produces naturally in response to darkness. This dual identity is what makes melatonin unusual: it’s one of the only hormones you can buy off a store shelf without a prescription, sitting alongside vitamins and herbal products. That classification has significant implications for how it’s regulated, what’s actually inside the bottle, and how other countries handle it.
Hormone First, Supplement Second
Your brain’s pineal gland produces melatonin every evening as light fades, signaling to your body that it’s time to wind down and sleep. It doesn’t knock you out the way a sleeping pill does. Instead, it functions more like a timing signal, helping regulate your internal clock.
The melatonin you find at a pharmacy or grocery store is almost always made synthetically through well-established chemical processes. Some products blend synthetic melatonin with botanical ingredients marketed for sleep support. A smaller number derive melatonin from plant sources like algae grown in controlled conditions, though most “plant-based” products on the market still rely primarily on synthetic melatonin with herbal additions. Older formulations sourced from animal pineal glands have largely disappeared from the market.
Why the U.S. Treats It Differently Than Other Countries
In the United States, the FDA classifies melatonin as a dietary supplement. That means it faces far less regulatory scrutiny than a prescription or over-the-counter drug. Manufacturers don’t need to prove it works before selling it, and there’s no required testing to confirm that the amount on the label matches what’s inside.
Most other developed countries disagree with this approach. In Australia, melatonin is either a pharmacist-only medicine or a prescription-only medicine depending on the dose and intended use. A pharmacist can sell modified-release tablets of 2 mg or less for adults 55 and older with insomnia, or immediate-release products of 5 mg or less for jet lag in adults. Everything else, including any use in children, requires a prescription. Much of Europe similarly restricts melatonin to prescription-only status or tightly controlled pharmacy sales. The U.S. is an outlier in allowing anyone, including parents buying it for their children, to pick it up as casually as a multivitamin.
What’s Actually in the Bottle
The lighter regulation creates a real accuracy problem. A 2017 study that tested 31 melatonin supplements from grocery stores and pharmacies found that most contained amounts of melatonin that didn’t match their labels. Even more concerning, 26 percent of those products contained serotonin, a different hormone that can cause harmful effects even at low levels.
A 2023 study zeroed in on gummy products specifically and found the problem persists. Out of 25 melatonin gummy products tested, 22 were inaccurately labeled. The actual melatonin content ranged from 74 percent to 347 percent of what was advertised. One product contained no detectable melatonin at all. So a gummy labeled at 5 mg could actually deliver anywhere from about 3.7 mg to nearly 17.5 mg, or nothing.
This inconsistency matters because melatonin’s effects are dose-dependent, and more is not better. Taking several times the intended dose can worsen side effects and disrupt the very sleep cycle you’re trying to fix.
Common Side Effects and Interactions
At typical doses, melatonin is generally well tolerated in the short term. The most common side effects are headache, dizziness, nausea, and daytime drowsiness. Less common reactions include vivid dreams or nightmares, short-term feelings of depression, irritability, stomach cramps, mood swings, and reduced alertness the next day.
Melatonin can interact with several types of medication. These include blood thinners, seizure medications, birth control, blood pressure medications, diabetes medications, immunosuppressants, and drugs processed by the liver. If you take any of these, the interaction risk is worth a conversation with your pharmacist or doctor before adding melatonin.
How Dosing and Timing Work
The timing of your dose matters as much as the amount. If you’re using melatonin to shift your sleep schedule earlier (the most common use), taking it three to four hours before your desired bedtime works best. If you need a more immediate sedating effect, such as sleeping on a long flight, 30 to 45 minutes before you want to sleep is the usual window.
Adults typically start at 1 mg and can increase by 1 mg per week if needed, with 10 mg as the general upper limit. Many people take far more than they need. Because your body already produces this hormone, even small supplemental doses can meaningfully shift your sleep timing. Higher doses don’t necessarily produce better sleep and can cause more grogginess the next morning.
Melatonin and Children
Melatonin has become increasingly popular as a children’s sleep aid, which is one reason the labeling accuracy problem is so concerning. The American Academy of Pediatrics advises that melatonin should only be used after establishing healthy bedtime routines first, and in partnership with a pediatrician.
Children who do benefit often respond to very low doses. The AAP suggests starting at 0.5 to 1 mg, taken 30 to 90 minutes before bedtime. Most children, even those with ADHD, don’t need more than 3 to 6 mg. The main side effects in children are morning sleepiness, drowsiness, and increased nighttime urination.
Less is known about long-term safety in kids. There are open questions about whether ongoing melatonin use could affect growth and development, particularly around puberty. In Australia, melatonin is only approved for children by prescription and only for specific conditions like autism spectrum disorder or Smith-Magenis syndrome. The AAP’s position reflects similar caution: use it carefully, use it sparingly, and don’t treat it as a permanent solution.
Choosing a More Reliable Product
Because the FDA doesn’t verify supplement labels, the burden of quality control falls on you. Look for products that carry a third-party testing seal from organizations like USP, NSF International, or ConsumerLab. These certifications mean an independent lab has verified that the product contains what it claims and is free of harmful contaminants. Products without third-party verification are essentially asking you to trust the manufacturer’s word, which the research suggests is not always reliable.
Tablets tend to be more accurately dosed than gummies, based on available testing data. If you’re giving melatonin to a child, accurate dosing is especially important given how much smaller their bodies are and how sensitive they may be to excess amounts. Store melatonin out of children’s reach, as accidental ingestion of multiple gummies (which often look and taste like candy) has become an increasing concern.