Melatonin and Sleep
An honest, pharmacologically accurate guide to what melatonin does, what it does not do, the dosage reality most people get wrong, and when it is genuinely useful.
What Melatonin Is – and What It Is Not
Melatonin is a hormone produced by the pineal gland in response to darkness. Its primary biological role is to signal the time of day to the circadian system – communicating that it is night. The circadian clock uses this signal to coordinate overnight processes: growth hormone release, core temperature decline, immune cytokine production, and the timing of sleep readiness.
What melatonin actually does
Melatonin shifts the biological clock to align sleep readiness with the correct time of day. It does not directly cause sleep. It acts as a darkness signal to the suprachiasmatic nucleus (the brain’s master clock), telling it that night has begun and sleep processes should be initiated. In a healthy adult in a normal light-dark environment, melatonin begins rising approximately 2 hours before habitual sleep onset – this is called DLMO (Dim Light Melatonin Onset).
The supplement version
Exogenous melatonin (the supplement) works by providing the brain with an artificial darkness signal at the time of ingestion. If you take it 30-60 minutes before your desired bedtime, it provides a phase-advance signal – shifting your biological clock slightly earlier. For jet lag (where your clock is set to the wrong timezone) or delayed sleep phase (where your clock runs late), this is exactly what is needed. For primary insomnia without a circadian component, the evidence is considerably weaker.
The Dosage Reality: Most People Take 10-20 Times Too Much
Most OTC melatonin is sold at 5-10mg. Research consistently shows that 0.5mg is as effective as 5mg for circadian phase shifting and sleep onset improvement, and 0.3mg is closest to the brain’s natural nocturnal melatonin production. Higher doses do not improve efficacy – they produce a pharmacological melatonin flood that may cause morning grogginess and, with chronic high-dose use, may suppress endogenous production. Brzezinski et al. (2005) in Sleep Medicine Reviews confirmed this dose-response relationship.
| Dose | Efficacy Rating | Clinical Notes |
|---|---|---|
| 0.1-0.3mg | Effective | Closest to physiological melatonin production. Peak endogenous nocturnal melatonin is approximately 0.1-0.3mg equivalent. Difficult to find OTC but splitting tablets achieves this range. |
| 0.5mg | Optimal | Most research-supported therapeutic dose for phase shifting. Equally effective to 5mg in head-to-head studies with fewer side effects. This is the target dose for most adults. |
| 1-3mg | No added benefit | No more effective than 0.5mg for circadian phase shifting. Commonly available. Some adults use this range without significant next-day impairment. Splitting a 3mg tablet in half or quarters reaches the optimal dose range. |
| 5mg | Excess dose | The most common OTC dose. No efficacy advantage over 0.5mg. Morning grogginess risk increased. This is 10-16 times the dose closest to physiological production. If currently taking 5mg and feeling groggy, reduce dose first. |
| 10mg+ | No clinical basis | No evidence supporting this dose for sleep or circadian benefits. Significant next-day grogginess common. With chronic use, may suppress endogenous melatonin production. Sold in some markets without adequate dosing guidance. |
When to Take Melatonin – Timing Calculator
Timing matters more than dose for melatonin efficacy. The correct time depends on your goal: gentle sleep onset support, circadian phase advance, or jet lag adjustment. Select your use case below.
For general sleep onset support: take melatonin 30-60 minutes before your desired bedtime. This provides a darkness signal at the intended sleep time.
For phase advance (shifting sleep earlier over days to weeks): take melatonin 5-6 hours before your current natural sleep onset. This is the most effective timing for circadian clock advancement.
For jet lag: take 0.5mg at the destination’s intended bedtime from night 1 of arrival. Continue for 3-5 nights. This is supported by the Herxheimer and Petrie (2002) Cochrane systematic review.
Recommended timing
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Recommended dose: 0.5mg. If 0.5mg is unavailable, split a 1mg or 3mg tablet. Always use the lowest effective dose.
When Melatonin Works – and When It Does Not
The evidence for melatonin is specific to its chronobiotic (clock-shifting) role. It is not a general sleep enhancer. Understanding this distinction prevents wasted money and false expectations.
Evidence supports melatonin for:
Melatonin is less effective or not appropriate for:
Side Effects by Dose
Melatonin at appropriate doses (0.5mg) has a favourable safety profile in short-term use in healthy adults. Side effects are largely dose-related – the most common issues with melatonin are caused by taking too much, not by the compound itself.
At 0.5mg (recommended)
Common (2-5% of users)
Rare at 0.5mg
At 5-10mg (common OTC dose)
More common
Chronic high-dose use concerns
Who Should Consult a Doctor Before Using Melatonin
Insufficient human safety data for melatonin in pregnancy. Animal studies suggest possible effects on fetal development. Avoid unless specifically directed by your obstetrician or GP.
Consult a GP before use in children or adolescents. Age-appropriate dosing is significantly lower than adult doses. Short-term use under medical supervision may be appropriate for specific conditions (DSPD in adolescents, autism-related sleep difficulties) but requires professional guidance.
Melatonin stimulates immune system activity. In autoimmune conditions (rheumatoid arthritis, lupus, MS, inflammatory bowel disease), this may worsen symptoms. Discuss with your specialist before use.
Clinically significant interactions with: warfarin and anticoagulants (increased bleeding risk), anticonvulsants (altered seizure threshold), diabetes medications (glucose regulation effects), immunosuppressants (cyclosporin interaction), nifedipine (blood pressure effect), and CNS depressants. Show your full medication list to a pharmacist before starting melatonin.
Sleep Cycle Timing
Pair Melatonin with Cycle-Aligned Wake Times
Melatonin helps with circadian phase. The sleep cycle calculator ensures your alarm lands at the end of a cycle in N1 sleep – minimising grogginess regardless of melatonin use.
Open Sleep Cycle CalculatorFrequently Asked Questions
Does melatonin help you fall asleep?
Melatonin can help with sleep onset in specific situations – particularly when the cause of delayed sleep onset is circadian timing. If you consistently struggle to fall asleep before midnight to 2am, melatonin taken 5-6 hours before your desired sleep onset may gradually advance your clock over days to weeks of consistent use. For jet lag, 0.5mg at the destination bedtime is supported by the Herxheimer and Petrie (2002) Cochrane systematic review as moderately effective. However, for general sleep onset difficulty without a circadian component – where you find it hard to fall asleep despite appropriate timing and no circadian phase problem – melatonin has weaker evidence. In these cases, CBT-I (cognitive behavioural therapy for insomnia) has substantially stronger research support and addresses the underlying causes of sleep onset difficulty rather than adding a hormone signal.
How much melatonin should I take for sleep?
Research supports 0.5mg as the optimal general dose – as effective as 5mg for circadian phase shifting, with fewer side effects (Brzezinski et al., 2005, Sleep Medicine Reviews). If your pharmacy only stocks higher doses, cutting a 3mg tablet into sixths or a 1mg tablet in half provides approximately the evidence-based dose range. Taking more than 0.5-1mg does not improve sleep onset further and increases the risk of morning grogginess, vivid dreams, and possible suppression of your body’s natural melatonin production over time. If you are currently taking 5-10mg and experiencing next-day drowsiness or grogginess, the dose is very likely the primary cause – reducing to 0.5mg is the recommended first step. Always consult a pharmacist about dosing, particularly if you take prescription medications, as melatonin has clinically significant interactions with several drug classes.
When should I take melatonin for sleep?
The correct timing depends on your goal. For general sleep onset support: take 0.5mg 30-60 minutes before your desired bedtime. For shifting your clock earlier over time (phase advance): take 0.5mg 5-6 hours before your current natural sleep onset time – this is the most effective timing for advancing the circadian clock and is based on the DLMO (dim light melatonin onset) minus-five-hours protocol from circadian research. For jet lag: take 0.5mg at the destination’s intended bedtime beginning on the evening of arrival, and continue for 3-5 nights. For shift work timing: take 0.5mg at the beginning of your intended sleep period. The core principle is that melatonin works by shifting your circadian clock, so the timing relative to your current biological phase matters more than the absolute clock time. The timing calculator above calculates the specific time for each use case.