Melatonin Dosage: Why 5 mg Is Usually the Wrong Dose (2026)
Melatonin is the sleep supplement most likely to work and most likely to be taken wrong. The error is almost always the dose: shelves sell 5 mg and 10 mg tablets, while the research that established melatonin’s effects used doses a thousand times smaller.
This guide explains the gap, the timing rules, and the label problem that makes buying the right dose harder than it should be.
The thousandfold gap
Endogenous melatonin peaks at night at blood concentrations around 10 to 60 picograms per millilitre. A 0.3 mg oral dose produces blood levels in the physiological range. A 5 mg dose produces levels ten to twenty times higher than the body ever makes on its own.
That does not make the larger dose dangerous — melatonin has a good safety record at these levels — but it changes what the drug does:
- At physiological doses (0.1–0.5 mg), melatonin acts on the suprachiasmatic nucleus as a timing signal. It shifts the clock.
- At pharmacological doses (3 mg and above), it occupies receptors more broadly, spills into peripheral tissues, and produces the soporific effect people are usually seeking — but it also produces more next-day grogginess and can cause the clock-shifting effect to become unpredictable.
The widely cited work on this — including studies by Zhdanova and colleagues — found that 0.3 mg was as effective as 3 mg for sleep onset in many subjects, and sometimes more effective, with fewer next-day effects. The dose-response curve for melatonin is not linear. Higher is not stronger.
What each dose is for
| Goal | Typical dose | Timing |
|---|---|---|
| Jet lag, eastward travel | 0.5–3 mg | At target bedtime at destination, 3–5 nights |
| Delayed sleep phase (night owl) | 0.5 mg | 4–6 hours before target bedtime |
| Shift work, rotating | 1–3 mg | Before the intended sleep period |
| General sleep onset difficulty | 0.5–1 mg | 30–60 minutes before bed |
| Children (medical supervision) | 0.5–1 mg | Per clinician |
Note what is missing: no row says 5 mg or 10 mg. Those products exist because they sell, not because they were the tested dose.
Timing matters more than dose
Melatonin is a clock signal first and a sedative second. Given at the wrong time it does the opposite of what you want.
- For sleep onset tonight, take it 30 to 60 minutes before bed. This is the “I cannot fall asleep” use case.
- For shifting the clock earlier, take it 4 to 6 hours before your current sleep onset, not before bed. This is the treatment for delayed sleep phase, and taking it at bedtime does very little.
- For jet lag travelling east, take it at the destination bedtime for three to five nights. Travelling west, the clock usually shifts on its own and melatonin is less useful.
- Never take it in the morning unless a clinician is deliberately shifting your rhythm. Morning melatonin delays the clock and worsens the problem.
The phase-shift effect is also why melatonin is not a good “take whenever” sleep aid. Used randomly, it sends inconsistent timing signals.
The label accuracy problem
In the US, melatonin is regulated as a dietary supplement, not a drug. That means the FDA does not verify content before sale. A frequently cited 2017 analysis of commercial melatonin products in Canada found that the actual content ranged from 83 percent below to 478 percent above the label claim, and that some products contained serotonin as a contaminant.
So the label is not a reliable specification. What helps:
- Third-party testing marks — USP Verified, NSF Certified, or Informed Choice. These are the only labels that indicate independent content verification.
- Single-ingredient products. Blends obscure both the dose and any contamination.
- Small tablets or liquid with a stated concentration, so you can halve a dose. A 5 mg tablet that cannot be split is a 5 mg dose.
- Reputable pharmacy brands over marketplace listings with no manufacturer named.
What to look for
| Feature | Target | Why |
|---|---|---|
| Dose per serving | 0.5–1 mg, splittable | Physiological range; adjustable |
| Serving size | Per tablet, not per 2 tablets | Common misdirection |
| Third-party testing | USP / NSF / Informed Choice | The only content assurance |
| Form | Plain tablets or liquid | Gummies vary in content and add sugar |
| Excipients | Minimal | Some contain allergens and sweeteners |
| Release type | Immediate release for sleep onset | Sustained release is for maintenance, and is not well supported |
| Packaging | Child-resistant, stored out of reach | Paediatric ingestion is the main safety concern |
Sustained-release melatonin is marketed for “staying asleep.” The evidence is weaker than for immediate release, and the formulations are inconsistent. If your problem is waking at 3 a.m., the better first steps are the ones in our guide to whether sleep supplements work — and a look at bedroom conditions, including temperature and light.
Safety and interactions
Melatonin is generally well tolerated at low doses. What is worth knowing:
- Next-day grogginess is the most common complaint, and it is dose-related. If you feel foggy, halve the dose before abandoning it.
- Vivid dreams and nightmares are reported, more often at higher doses.
- Drug interactions: melatonin is metabolised by CYP1A2. It interacts with fluvoxamine (a strong inhibitor, which can raise melatonin levels dramatically), warfarin, some anticonvulsants, and immunosuppressants. It can also affect blood glucose control in diabetes.
- Pregnancy and breastfeeding: not recommended without medical advice.
- Children and adolescents: increasingly prescribed, but should be clinician-led. Dosing is weight-dependent and long-term effects on pubertal timing are not fully characterised.
- Autoimmune conditions: melatonin has immunological effects; caution is advised.
Practical protocol
- Start at 0.5 mg, 45 minutes before bed, for sleep onset.
- Keep the timing fixed for at least a week. Consistency is the active ingredient.
- If nothing happens, do not escalate to 5 mg. Consider whether the problem is sleep onset (melatonin may help) or sleep maintenance (melatonin likely will not).
- Use it for a defined period — three to five nights for jet lag, a few weeks for phase shifting — rather than indefinitely.
- Get light right as well. Melatonin is suppressed by bright light; taking a tablet and then looking at a phone for an hour wastes most of the dose.
If you are considering magnesium alongside it, our magnesium guide covers the elemental-dose problem that makes most labels misleading. And if you want the non-supplement route to shifting your clock, a light therapy lamp used in the morning does the same job from the other direction.
FAQ
Is 10 mg too much? It is not dangerous for most adults, but it is well above the range used in trials and produces more next-day effects. There is little reason to start there.
Can I take melatonin every night? Short-term use is well studied; long-term nightly use in adults is common but less well characterised. For chronic insomnia the better-supported first-line treatment is CBT-I, not a supplement.
Does melatonin stop working if I take it too long? Tolerance is not well documented the way it is with sedatives, but the behavioural dependence — needing it to sleep — is real.
Will it help my child sleep? It is increasingly used in neurodevelopmental conditions under medical supervision. Do not self-prescribe for a child; dosing and timing are both different.
Can I take it with alcohol? They both affect sleep architecture and combining them increases next-day impairment. Avoid.
