Three months in, the dose has crept from 1 mg to 5 mg to one of the 10 mg gummies from the display rack near the pharmacy checkout. Falling asleep still takes forty minutes. The 1 a.m. wake-up is unchanged. The instructions on the bottle promised sleep support, and the label says nothing about why more melatonin has not translated into more sleep.

Melatonin Is a Timing Signal, Not a Sedative

Melatonin is not a sleeping pill in the way a benzodiazepine or a z-drug is. It does not sedate the brain by boosting GABA activity. It is a chronobiotic, a substance that carries the signal "it is dark" to the suprachiasmatic nucleus, the master clock that sits behind the eyes and sets the timing of the entire sleep-wake cycle. In the body's own rhythm, melatonin rises in the evening as light fades and tells the rest of the system that biological night has started.

Exogenous melatonin, the kind in a capsule or gummy, works the same way. Taken at the right point in the circadian cycle, it can shift the timing of sleep earlier or later depending on when it is dosed relative to a person's internal clock, a relationship described by a phase response curve. A 2024 dose-response meta-analysis of 26 randomized trials found that both the timing and the dose in common use are off the mark. The regimen most people use, 2 mg taken 30 minutes before bed, sits well outside the window where melatonin does most of its work. The analysis found stronger effects on sleep onset latency and total sleep time at 4 mg, taken three hours before the desired bedtime, not thirty minutes.

This distinction, timing signal versus sedative, is not a technicality. It explains why melatonin can work well for problems of circadian timing and poorly for problems of arousal, which is the more common driver of chronic insomnia.

The Evidence for Chronic Insomnia in Adults Is Weak

The American Academy of Sleep Medicine's 2017 clinical practice guideline for the pharmacologic treatment of chronic insomnia in adults reviewed the trial evidence for melatonin at the 2 mg dose most commonly sold and used. Its conclusion: clinicians should not use melatonin as a treatment for sleep onset or sleep maintenance insomnia, a weak recommendation reflecting low-quality evidence and a small measured benefit. A parallel 2022 systematic review and meta-analysis of 24 randomized controlled trials in chronic insomnia sorted results by age group and found that in adults, melatonin showed no measurable effect on sleep onset latency, total sleep time, or sleep efficiency, whether or not insomnia was comorbid with another condition. The same review found a benefit in children and adolescents, a different population with a different evidence base and, in Canada, a different regulatory status since 2026.

Earlier meta-analyses framed melatonin more favourably. Ferracioli-Oda and colleagues, pooling 19 studies of primary sleep disorders, found melatonin reduced sleep onset latency by about 7 minutes and increased total sleep time by about 8 minutes compared to placebo, describing the effect as real but modest, smaller than the effect sizes reported for benzodiazepines and z-drugs. A 2022 update from the Canadian Agency for Drugs and Technologies in Health reviewed nine more recent reviews and trials and found the same pattern that runs through this literature: mixed results that depend heavily on how sleep is measured. Melatonin sometimes helped on subjective, self-reported sleep quality and did not move objective sleep onset latency measured by EEG or actigraphy. A small subjective improvement that does not show up on an objective measure is a real finding, but it is not the same as fixing insomnia. For a wider view of where melatonin sits against other approaches, how the major insomnia treatments compare lays that out.

Melatonin Helps Most When Insomnia Overlaps With Circadian Misalignment

The evidence looks different once the picture narrows to circadian rhythm disorders rather than chronic insomnia generally. The American Academy of Sleep Medicine's own guideline on intrinsic circadian rhythm sleep-wake disorders positively endorses strategically timed melatonin for delayed sleep-wake phase disorder, for non-24-hour sleep-wake disorder in blind adults, and for irregular sleep-wake rhythm disorder in children and adolescents with comorbid neurological conditions. These are conditions where the internal clock has drifted out of alignment with the external day, not conditions where the clock is aligned but the nervous system will not power down. Someone with delayed sleep-wake phase disorder who cannot fall asleep before 2 a.m. no matter how tired they are, or a shift worker trying to sleep against daylight, is dealing with a timing problem. Melatonin, a timing signal, is a reasonable tool there.

Even in that narrower group, the same guideline treats light exposure, not melatonin, as the better-characterized and more robust way to shift the clock. Light suppresses melatonin secretion and moves circadian timing according to its own well-mapped phase response curve, with larger and more reliable shifts than melatonin produces at typical doses. It carries no supplement quality-control problem, no wrong-dose risk, and no cost beyond getting outside or in front of a light box at the right time of day. Trials that combine light and melatonin, dosed to reinforce the same phase shift rather than working against it, tend to outperform either one alone.

For insomnia without that circadian component, someone who is tired at 10 p.m., gets into bed, and lies awake anyway, melatonin is being asked to do a job it is not built for. There is no darkness signal missing in that picture. There is a nervous system that has learned to associate the bed with wakefulness, the pattern behind most middle-of-the-night waking.

Melatonin Sold in Canada Is Regulated Differently Than the US Gummies Driving Recent Safety Data

Much of the alarming recent data on melatonin content comes from the United States, where melatonin is sold as an unregulated dietary supplement with no requirement that the label match the contents. A 2023 study published in JAMA tested 25 melatonin gummy brands sold in the US and found 88 percent inaccurately labelled, with actual content ranging from 74 to 347 percent of the labelled dose. One product contained no detectable melatonin at all. A 2024 follow-up testing products marketed towards children found content ranging from 0 to 667 percent of label claim. This is not a problem that has improved with time. It has gotten worse as the US gummy market has grown.

Melatonin sold in Canada sits under a different system. Health Canada classifies it as a natural health product, which means every legal product needs a Natural Product Number, and the manufacturer has to demonstrate the finished product meets its declared specifications for identity, purity, and quantity before it can be sold. That system was tested directly. In a Health Canada compliance review of 24 natural health products including melatonin supplements, purchased off the shelf across several provinces and independently lab-tested, 23 of 24 passed testing for accurate melatonin content; the one failure was measured at 84 percent of its label claim, still within a range that would not meaningfully change how it works. That is a narrower, more direct test of the Canadian system than the widely cited 2017 University of Guelph study, which found much larger discrepancies, up to 478 percent of label claim, but tested whatever was on grocery and pharmacy shelves rather than isolating NPN-licensed products specifically. Both studies matter. The Guelph study is the reason quality is worth checking for at all; the Health Canada review is closer to evidence that the NPN system is doing its job on melatonin specifically.

The regulatory picture for children has also moved. As of June 2, 2026, Health Canada reclassified melatonin sold for any sleep-related use in anyone under 18 as a prescription drug, replacing a narrower rule that had applied only to a small set of pediatric conditions. Adult-use melatonin natural health products are unaffected by that change.

What Treats Chronic Insomnia

Conditioned arousal, not a shortage of melatonin, is the leading explanatory model for why chronic insomnia persists once it has been present for more than a few months. The bed and the bedroom become associated with the frustration of lying awake, the mind starts running through the day's problems the moment the lights go off, and the body's stress system stays active at exactly the point it should be winding down. None of that responds to a darkness signal, because the clock is not the part that is broken. How the beliefs a person holds about sleep feed that arousal is worth understanding on its own.

CBT-I addresses the arousal and the learned association directly, through stimulus control, sleep restriction, and cognitive work on the beliefs that keep the nervous system on alert at bedtime, rather than trying to chemically override a clock that is already correctly timed. For the smaller group of people whose insomnia is tangled up with a shifted circadian clock, whether from shift work, a delayed sleep phase, or another circadian disorder, that piece can be addressed alongside CBT-I with correctly timed light exposure and, where appropriate, melatonin dosed at the right point on the curve rather than the standard thirty minutes before bed.