Melatonin 101
Melatonin is one of the most common over-the-counter remedies for sleep, and one of the topics I get the most questions about. Widespread use doesn’t mean melatonin is harmless, effective, or appropriate for everyone. Before you reach for another gummy, it’s worth understanding how melatonin works and how to maximize its effect.
How does melatonin work?
While melatonin is marketed as a sleep supplement, it’s actually a circadian (internal clock) hormone. You make melatonin already, in your pineal gland deep in the center of your brain. In the evening, the pineal gland releases melatonin, setting the stage for sleep and other nighttime circadian activities.
Circadian effects of melatonin:
Taking extra (exogenous) melatonin has opposite effects on the circadian rhythm, depending on the time that it is taken. In the phase-response curve (PRC) below, the red line shows the effect of melatonin given at the time indicated on the X-axis.
Phase response curve. Red = melatonin, Yellow= Light.
As you can see, melatonin taken a couple hours before sleep (the red peak around 7-8pm) will have the strongest “advance” effect on the circadian rhythm. This means that it will make the circadian rhythm earlier.
So, for someone who is a night owl*, who typically has trouble falling asleep at the beginning of the night, melatonin can help advance their circadian rhythm and therefore fall asleep faster.
*aka delayed sleep phase syndrome (DSPS) or “circadian disorder, delayed sleep phase type”
In terms of science to back up use of melatonin in DSPS: A meta-analysis of 14 randomized clinical trials showed that the effect of melatonin on people with DSPS was falling asleep 39 minutes faster on average (Buscemi 2005).
Sleep effects of melatonin:
Melatonin has very mild sleep-promoting effects, meaning, it is not going to knock anyone asleep.
One main way melatonin promotes sleep is by lowering body temperature. There are other hypothesized mechanisms by which melatonin promotes sleep, but studies are not definitive, particularly because supplement-type melatonin is not frequently used in high-quality randomized clinical trials.
And the data aren’t great. For people with insomnia (not night owls), in the initial meta-analysis in 2005, the effect of melatonin was that they fell asleep 7 minutes faster. (Buscemi 2005). In the intervening years, a few more studies have been done with melatonin. A very high-quality, large meta-analysis of all sleep drugs in insomnia (De Crescenzo 2023) showed no effect of melatonin in people with insomnia.
To summarize: Melatonin is effective in helping people with delayed sleep phase fall asleep faster by advancing their circadian rhythms. It has minimal or no effect for people with insomnia due to other reasons.
What’s the right dose of melatonin to take?
As with any medication, the right dose is the lowest effective dose. A wide range of doses have been tested, and melatonin is additionally complicated by the fact that the effect depends on the time that it is taken.
In general, the doses tested have been in the 0.5 to 5mg range. (Cruz-Sanabria 2023). In a large meta-analysis of 26 randomized clinical trials (Cruz-Sanabria 2024), the dose response maxes out at 4mg.
Again, the effect is maximal if melatonin is taken a couple hours before bedtime, reinforcing that the best effect of melatonin is for advancing circadian phase.
In fact, too much melatonin can be harmful, particularly because melatonin has opposing effects later at night. If you look at the phase-response curve, there is a red “valley” from 2am to 2pm. This means that melatonin in the system will delay (make later) the circadian rhythm.
Taking too much melatonin at night so that it lasts for hours in the body sends mixed signals—both advancing and delaying the circadian rhythm—and may backfire and worsen insomnia.
In fact, in blind people who require consistent melatonin supplementation for their circadian rhythms, people who did not respond to a high (10mg) dose did better with a low (0.5mg) dose. (Lewy 2002)
Also, people who take an extra melatonin when they wake up in the middle of the night, are just confusing their circadian rhythms and may be making their insomnia worse.
To summarize: the right dose of melatonin is lowest effective dose in the 0.5 to 5mg range, a couple hours before bedtime.
Exceptions:
People who have free-running circadian rhythm disorder (typically due to blindness) need low doses.
People who take melatonin for REM sleep behavior disorder. The melatonin effect in this case is separate and higher/repeated doses may be needed
I don’t comment on prescription prolonged-release melatonin which is not available in the US
What’s the best melatonin pill?
Unfortunately, melatonin is considered a nutritional supplement in the US, so what you can buy is not very well regulated. A study in the Journal of Clinical Sleep Medicine (Erland & Saxena 2017) tested 31 different melatonin supplements and found that 26% were contaminated with serotonin, and 71% contained wrong doses (more than 10% different from what was on the label).
That study was helpful in that we learned that the following will be most likely to get you better purity and consistent dosing:
At least a 3mg tablet*
Tablet formulation, not liquid, melty strips, or gummy
Just melatonin, not a combo** with other supplements
*This means that to take a lower dose, you need to cut a tablet in half or quarters. Use a clean, dry, sharp knife (chef’s knife works better than a small knife, in my experience) or a pill cutter, NOT your teeth.
**The combination supplements had a high rate of contamination with serotonin.
As for the brand of melatonin: USP (US Pharmacopoeia) or NSF are both non-profit organizations that test supplements. You can search their websites for free.
Currently (February 2026), there is only one melatonin 3mg tablet formulation that is USP certified (NatureMade), so that is the one I take. To be clear, I have no financial or other relationship with NatureMade; I chose it based on the USP certification and formulation only.
Which brings me to… Importantly, don’t get melatonin (especially in a blended formulation) being peddled by someone who makes money from it! The American Medical Association prohibits sale of health-related items by physicians, due to ethical concerns. And definitely don’t get supplements being hawked by podcasters, sleepfluencers, and the like.
Any drug, even a supplement, with potential for help also has a potential for harm. Your health is important, so make careful decisions uninfluenced by those who will profit from you.
What are side effects of melatonin?
Fortunately, melatonin is generally well-tolerated, even at higher-than-necessary doses. But a death in 2023 of someone who intentionaly overdosed on melatonin and diphenhydramine (benadryl) was a sobering reminder that we need to be careful, even with supplements and OTC meds.
Technically the most common reported side effects of melatonin are drowsiness, change in dreams, headache, and stomach upset.
The most common complaints about melatonin that I hear as a sleep doctor are:
Feeling cold - yes, this happens, and is probably how it helps with sleep
Insomnia - this is usually in the early morning and in my experience is usually in people who are advanced circadian phase (“morning larks”) who accidentally pushed their circadian clocks earlier
“It doesn’t knock me out” - yup, this is a feature, not a bug.
The Takeaway
If you decide to try melatonin as a sleep/circadian supplement:
Get a plain tablet, at least 3mg, and start with half tablet. Use a sharp knife or a pill cutter.
Get a brand and formulation that is USP or NSF Certified
Do not combine with other sedatives including alcohol
Melatonin works best for night owls who have trouble initially falling asleep, especially if taken a couple hours before bedtime. Timing, and consistency of timing, is critical with melatonin!
If a low dose doesn’t work, you can gradually increase. But if 5mg (and certainly if 10mg) is not having any effect, melatonin does not work for you and you can throw in the towel.
References
Buscemi N, Vandermeer B, Hooton N, Pandya R, Tjosvold L, Hartling L, Baker G, Klassen TP, Vohra S. The efficacy and safety of exogenous melatonin for primary sleep disorders. A meta-analysis. J Gen Intern Med. 2005 Dec;20(12):1151-8. doi: 10.1111/j.1525-1497.2005.0243.x. PMID: 16423108; PMCID: PMC1490287. Fulltext.
Cruz-Sanabria F, Bruno S, Crippa A, Frumento P, Scarselli M, Skene DJ, Faraguna U. Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug: A Systematic Review of Randomized Controlled Trials and Dose-Response Meta-Analysis. J Pineal Res. 2024 Aug;76(5):e12985. doi: 10.1111/jpi.12985. PMID: 38888087.
Cruz-Sanabria F, Carmassi C, Bruno S, Bazzani A, Carli M, Scarselli M, Faraguna U. Melatonin as a Chronobiotic with Sleep-promoting Properties. Curr Neuropharmacol. 2023;21(4):951-987. doi: 10.2174/1570159X20666220217152617. PMID: 35176989; PMCID: PMC10227911. Fulltext.
De Crescenzo F, D'Alò GL, Ostinelli EG, Ciabattini M, Di Franco V, Watanabe N, Kurtulmus A, Tomlinson A, Mitrova Z, Foti F, Del Giovane C, Quested DJ, Cowen PJ, Barbui C, Amato L, Efthimiou O, Cipriani A. Comparative effects of pharmacological interventions for the acute and long-term management of insomnia disorder in adults: a systematic review and network meta-analysis. Lancet. 2022 Jul 16;400(10347):170-184. doi: 10.1016/S0140-6736(22)00878-9. PMID: 35843245. Fulltext.
Erland LA, Saxena PK. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. J Clin Sleep Med. 2017 Feb 15;13(2):275-281. doi: 10.5664/jcsm.6462. PMID: 27855744; PMCID: PMC5263083. Fulltext.
Lewy AJ, Emens JS, Sack RL, Hasler BP, Bernert RA. Low, but not high, doses of melatonin entrained a free-running blind person with a long circadian period. Chronobiol Int. 2002 May;19(3):649-58. doi: 10.1081/cbi-120004546. PMID: 12069043. Pubmed.
