How Much Melatonin Should You Take? An Evidence Check

Verdict: Moderate for circadian disorders. Weak for general insomnia. The effective dose is 0.5mg, not the 5-10mg found on most shelves.

The claim: melatonin helps you sleep. The dosing on the bottle is the right amount. Neither statement holds up to the evidence the way you might expect.

The claim inventory

The standard claim takes two forms. The first: melatonin helps you fall asleep faster. The second: the dose on the bottle is what you need. The evidence partially supports the first claim, for specific populations, and contradicts the second almost entirely. The gap between what the dose-response research shows and what the supplement aisle offers is one of the largest in the sleep product market.

What melatonin actually does

Melatonin is a hormone produced by the pineal gland in response to darkness. The suprachiasmatic nucleus (SCN), the brain’s master circadian pacemaker, signals the pineal gland to begin melatonin synthesis as light levels drop in the evening. Melatonin rises, peaks in the middle of the night, and falls toward morning. This pattern signals to the rest of the body that it is nighttime: body temperature drops, alertness decreases, and the physiological conditions for sleep are set.

Melatonin is a timing signal, not a sedative [5]. This distinction matters because the marketing typically frames melatonin as something that puts you to sleep, like a mild sleeping pill. What it actually does is shift the circadian clock: it tells your body when to expect sleep, not how deeply to sleep. The difference is pharmacologically significant. A sedative reduces arousal regardless of timing. A chronobiotic, which is what melatonin is, adjusts when the body’s sleep window opens. If your circadian clock is already aligned with your desired sleep time, exogenous melatonin has little to add.

The distinction also explains why melatonin works better for some people than others. If the underlying problem is circadian misalignment (your body wants to sleep at 2 AM but you need to sleep at 11 PM), melatonin addresses the problem directly. If the underlying problem is hyperarousal, conditioned wakefulness, or behavioral factors maintaining insomnia, melatonin does not address the problem because the problem is not circadian.

The dosing problem

This is where the evidence is clearest and the market is most disconnected from it.

Zhdanova et al.’s dose-response work found that 0.3mg of melatonin was as effective as 1mg for promoting sleep onset in 20 healthy volunteers, and that higher doses did not produce greater effects [1]. This was a crossover study, meaning each participant served as their own control, which strengthens the comparison. The finding has been consistent: the dose-response curve for melatonin’s circadian effects flattens above approximately 0.5mg.

The Cochrane review on jet lag found that 0.5mg was equally effective as 5mg for sleep onset, though 5mg produced slightly faster onset in some studies [5]. The rapid evidence assessment by Costello et al. systematically evaluated the dose-response relationship and found no incremental benefit above 0.5-1mg for circadian shifting [3].

Most commercial melatonin products contain 3mg, 5mg, or 10mg. Some contain 20mg. This is 6 to 40 times the dose supported by the dose-response literature. At these supraphysiological doses, blood melatonin levels remain elevated well into the next day, which can cause morning grogginess, daytime drowsiness, and paradoxically, disruption of the circadian rhythm the supplement is supposed to support.

Because melatonin is sold as a dietary supplement in the US, there is no regulatory mechanism requiring evidence-based dosing. Manufacturers set doses based on market logic, not pharmacology. Higher doses may feel more effective to consumers, who associate “more” with “stronger.” For chronobiotics, this intuition is wrong. More melatonin does not produce more sleepiness. It produces a longer, flatter signal that the circadian system may not interpret as a clean timing cue.

The content variability problem

An underreported quality-control issue compounds the dosing problem. Erland and Saxena tested 31 melatonin products purchased from retail outlets and found that actual melatonin content ranged from -83% to +478% of the labeled dose [4]. A product labeled as 5mg might contain less than 1mg or more than 25mg. Some products contained serotonin, a neurotransmitter that was not listed on the label and that can cause adverse effects at sufficient doses.

This variability means that even if a consumer chooses a 0.5mg product based on the evidence, they have limited assurance that the product contains what it claims. In the European Union, melatonin is regulated as a medication and subject to pharmaceutical manufacturing standards. In the US, it is a supplement, and manufacturing standards are less stringent. Third-party testing certifications (USP, NSF, ConsumerLab) provide some quality assurance, but most products on shelves do not carry these certifications.

What the trials show for sleep

The meta-analysis by Ferracioli-Oda et al. pooled 19 RCTs with 1,683 subjects and found melatonin reduced sleep onset latency by an average of 7.06 minutes and increased total sleep time by 8.25 minutes [2]. The Auld et al. meta-analysis of 12 RCTs confirmed similar magnitudes [6]. These are real, statistically significant effects. They are also small in clinical terms. Most people would not perceive a 7-minute change in how long it takes to fall asleep.

Where the evidence is stronger

Melatonin has its best evidence for circadian rhythm disorders: jet lag, where the Cochrane review clearly supports its use [5]; delayed sleep-wake phase disorder, where the circadian clock runs persistently late; and shift work disorder, where the work schedule conflicts with the biological night. In these populations, the problem is timing, and melatonin addresses timing directly. The effect sizes are larger and more clinically meaningful when the underlying problem is circadian misalignment.

For travelers crossing multiple time zones, 0.5mg of melatonin taken at the destination’s bedtime can meaningfully reduce jet lag duration. This is one of melatonin’s most well-supported and practical applications.

The timing question

When you take melatonin matters as much as how much you take, and this is another area where common practice diverges from the evidence. The circadian-shifting effect of melatonin depends on when it is taken relative to the body’s own melatonin onset, a point called dim light melatonin onset (DLMO). Taking melatonin 1-2 hours before your desired sleep time advances the circadian clock, telling the body to expect sleep earlier. Taking it at bedtime, when the body’s own melatonin production is already rising, adds little to what the pineal gland is already doing.

Many people take melatonin immediately before getting into bed, as they would take a sleeping pill. This timing misses the window where melatonin’s chronobiotic effect is strongest. For someone trying to shift their sleep window earlier, taking 0.5mg at 8 or 9 PM (for a desired 10:30 or 11 PM bedtime) is more pharmacologically appropriate than taking it at 10:30 PM when lying down. The distinction between “take it before bed” and “take it well before bed” is clinically meaningful, and most product labels do not make it clear.

For shift workers and travelers, timing is the entire point. A shift worker returning to a day schedule after night shifts can use melatonin to accelerate the circadian readjustment, but only if the timing is appropriate for the direction of the shift. The Cochrane review noted that melatonin taken at the destination bedtime was effective for eastward travel across five or more time zones, where the circadian clock needs to advance [5].

Where the evidence is weaker

For primary insomnia without a circadian component, the mean effect of 7 minutes faster sleep onset is modest. The AASM clinical practice guideline does not recommend melatonin as a treatment for chronic insomnia. The evidence does not support it as a first-line option for someone who lies awake for hours most nights due to hyperarousal or conditioned wakefulness.

How it compares to CBT-I

CBT-I meta-analyses show reductions in sleep onset latency of approximately 19 minutes and reductions in wake after sleep onset of approximately 26 minutes, with effects maintained at multi-year follow-up. Melatonin’s meta-analytic effect is 7 minutes on sleep onset latency, with no long-term maintenance data. The comparison is not close, and the mechanisms address different problems: CBT-I restructures the behavioral and cognitive patterns that maintain insomnia; melatonin shifts circadian timing.

For people with both a circadian component and behavioral insomnia, the two approaches are not mutually exclusive. A CBT-I program that includes a circadian component (consistent wake time, morning light exposure, and appropriately timed low-dose melatonin) addresses both dimensions. In this context, melatonin serves as an adjunct to behavioral treatment, not as a standalone intervention. The dose and timing principles still apply: 0.5mg, taken 1-2 hours before desired sleep time, aligned with the sleep schedule that the CBT-I program establishes.

The bottom line

Melatonin is a modestly effective circadian-shifting agent when used at 0.5mg, taken 1-2 hours before desired sleep time. It is not an effective sedative. The doses sold commercially are not supported by dose-response evidence and may cause next-day grogginess and circadian disruption. The supplement itself may not contain what the label claims. If your problem is circadian timing, melatonin has a role at a fraction of the dose on most shelves. If your problem is chronic insomnia, the evidence points elsewhere.

If you’re struggling with sleep regularly, speak with a GP or pharmacist before adding supplements or medications. For persistent insomnia, AASM guidelines recommend CBT-I as the first-line treatment. The American Academy of Sleep Medicine has a provider finder at sleepeducation.org.