Melatonin for Sleep: Dose, Timing, and Purity Problems

By the second week of December, Portland gets under nine hours of daylight. The winter solstice on December 21 brings about 8 hours and 56 minutes of it, and the earliest sunsets of the year actually arrive around December 9, which means the sky starts going dark before many of us have left work. That long stretch of dark is hard on sleep. So a lot of Mainers do what seems sensible and grab a bottle of melatonin off the pharmacy shelf. It is cheap, it is everywhere, and it sounds harmless. The research is more interesting than that.

What melatonin actually is

Melatonin is a hormone your brain makes in response to darkness. According to the National Center for Complementary and Integrative Health, part of the National Institutes of Health, it helps set the timing of your circadian rhythm, the roughly 24-hour internal clock that tells your body when to feel sleepy. In a normal winter, your own melatonin should be rising earlier in the evening anyway.

Here is the part that surprises people. In the United States, melatonin is sold as a dietary supplement, not a prescription or over-the-counter drug. That single classification explains most of the problems below. A supplement is held to a looser standard by the Food and Drug Administration than a medication is, so nobody is checking each bottle’s purity or dose the way they would for an actual drug.

What the research shows about sleep

Melatonin does something. It is just smaller than the marketing implies. A 2013 meta-analysis in PLoS ONE pooled 19 studies covering 1,683 people and found that melatonin shortened the time it took to fall asleep by about 7 minutes and added roughly 8 minutes to total sleep time. Real, measurable, and modest. The authors noted the absolute benefit was smaller than what you get from other pharmacological treatments for insomnia.

The professional guidance reflects that. In its 2017 clinical practice guideline, the American Academy of Sleep Medicine suggested that clinicians not use melatonin to treat sleep-onset or sleep-maintenance insomnia in adults. They graded that recommendation “weak,” which is the polite clinical way of saying the evidence is thin and reasonable people might disagree. NCCIH lands in a similar place, noting there is not enough strong evidence to recommend melatonin for chronic insomnia.

None of that means melatonin is useless. It means it is a gentle nudge to your body clock, not a sedative, and it works best for some sleep problems and barely at all for others.

Timing matters more than the dose

This is the finding most people miss, and it is the most useful one. A 2024 systematic review and dose-response meta-analysis in the Journal of Pineal Research looked at 26 randomized controlled trials. The researchers found that when you take melatonin predicts how much it helps, not just how much you take. The gap between swallowing the pill and actually trying to sleep turned out to be a significant factor in how quickly people drifted off. In their analysis, results were best around a 4 mg dose taken roughly 3 hours before bedtime.

Read that again, because it runs against the usual habit. Most people take melatonin as they are turning off the light. The data suggest the body uses it more like a scheduling signal than an off switch, which is also why a smaller, earlier nudge can outperform a bigger one swallowed at midnight. We are not telling you what to take. We are pointing at what the trials measured. The timing piece is worth raising with your own clinician, especially if melatonin has not done much for you before.

The purity problem

Now the uncomfortable part. What the bottle says and what is in the bottle are often two different things.

A 2017 study in the Journal of Clinical Sleep Medicine tested 31 over-the-counter melatonin products. The actual melatonin content ranged from 83 percent below the labeled amount to 478 percent above it. Roughly 70 percent of the products missed the labeled dose by more than 10 percent. One product’s content varied lot to lot by as much as 465 percent, meaning two bottles of the same thing could be wildly different. The same researchers found serotonin, which was not listed on the label, in more than a quarter of the products tested (8 of the 31).

Gummies are no better, and they are what a lot of families buy because kids will take them. A 2023 study in JAMA analyzed 25 melatonin gummy products and found 22 of them (88 percent) were inaccurately labeled. Actual melatonin ranged from 74 percent to 347 percent of the stated dose. One product contained no detectable melatonin at all, but did contain CBD.

If you want to get sharper about reading these bottles, our guide on how to read supplement labels walks through what the dietary-supplement designation does and does not promise.

Why it is so loosely regulated

It comes back to that supplement label. Because melatonin is sold as a dietary supplement rather than a drug, it is regulated less strictly and is not FDA-approved for any use. Its purity and dose are not verified the way a medication’s would be before it reaches the shelf. That is not a loophole somebody snuck through. It is the entire legal category working as designed. The catch is that most shoppers assume a pill sold next to the cold medicine has been vetted like the cold medicine. It has not.

The pediatric wake-up call

The clearest reason to keep these bottles capped and out of reach is what happened as melatonin got popular. The CDC reported that calls to US poison control centers for children accidentally swallowing melatonin rose 530 percent between 2012 and 2021, climbing from 8,337 reports a year to 52,563, for a total of 260,435 over the decade. The most serious outcomes were in children aged 5 and younger. A 2024 CDC report estimated nearly 11,000 emergency department visits for unsupervised melatonin ingestion among infants and young children during 2019 to 2022.

A gummy that looks and tastes like candy, sold in a bottle a toddler can open, with an unpredictable dose inside, is a combination worth respecting. If melatonin lives in your house, treat it like medicine even though the law does not.

The honest summary for Maine sleepers

Melatonin is a modest tool with a real timing trick and a genuine quality-control problem. The dark months here are long, and the urge to fix sleep with something off a shelf is understandable. Before reaching for the bottle, the cheaper and better-supported move is usually the boring one: consistent light exposure, a steady schedule, and a cool dark room. Our piece on sleep hygiene for Maine winters covers the habits that move the needle without anything in a capsule. If you do try melatonin, a conversation with your clinician about timing and a third-party-tested product is time well spent.

Sources

• National Center for Complementary and Integrative Health (NIH). Melatonin: What You Need To Know. NCCIH. 2022. https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know
• Ferracioli-Oda E, Qawasmi A, Bloch MH. Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLoS ONE. 2013. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0063773
• American Academy of Sleep Medicine. Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults. Journal of Clinical Sleep Medicine. 2017. https://pmc.ncbi.nlm.nih.gov/articles/PMC5263087/
• Cruz-Sanabria F, et al. Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug. Journal of Pineal Research. 2024. https://onlinelibrary.wiley.com/doi/10.1111/jpi.12985
• Erland LAE, Saxena PK. Poor Quality Control of Over-the-Counter Melatonin: What They Say Is Often Not What You Get. Journal of Clinical Sleep Medicine. 2017. https://pmc.ncbi.nlm.nih.gov/articles/PMC5263069/
• Cohen PA, et al. Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. JAMA. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10130950/
• CDC. Pediatric Melatonin Ingestions, United States, 2012-2021. Morbidity and Mortality Weekly Report. 2022. https://www.cdc.gov/mmwr/volumes/71/wr/mm7122a1.htm
• CDC. Notes from the Field: Emergency Department Visits for Unsupervised Pediatric Melatonin Ingestion, United States, 2019-2022. Morbidity and Mortality Weekly Report. 2024. https://www.cdc.gov/mmwr/volumes/73/wr/mm7309a5.htm
• Gaisma. Portland, Maine: Sunrise, sunset, dawn and dusk times for the whole year. Gaisma. 2026. https://www.gaisma.com/en/location/portland-maine.html
• WGME (CBS 13 Portland). Earliest sunset on Saturday begins Maine’s darkest time of year. WGME. 2024. https://wgme.com/news/local/earliest-sunset-on-saturday-begins-maine-darkest-time-of-year-portland-bangor-new-england-december-winter-january-solstice

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any health decisions.