Walk into any pharmacy and melatonin supplements are stocked in 3mg, 5mg, and 10mg tablets. The most common dose sold is 5mg. Your pineal gland, the organ responsible for endogenous melatonin production, produces approximately 0.1-0.3mg per night. This means a standard supplement contains 15 to 50 times the physiological dose. Understanding why this mismatch exists — and what the research actually shows — can help you determine whether a smaller dose might work better for your sleep.

The Pineal's Natural Output

Melatonin production in humans follows a circadian rhythm. Plasma melatonin concentrations begin to rise in the evening, peak between 2-4am, then decline toward morning. At peak, concentrations reach roughly 100-200 pg/mL. The total amount of melatonin secreted per 24-hour cycle is approximately 0.1-0.3mg for most adults.

This is a well-established measurement from dozens of pharmacokinetic studies. The variation between individuals is real, but the order of magnitude is consistent: endogenous melatonin production is in the tenths of a milligram, not the single milligrams or tens of milligrams found in most supplements.

The gap between endogenous production and standard supplement doses raises a straightforward question: if your body makes 0.2mg per night, why take 5mg?

What Doses Actually Show Effect in Research

The evidence on melatonin dosing comes from a mix of clinical trials and mechanistic studies. Early work on melatonin as a sleep aid (1990s onward) used doses ranging from 0.5mg to 10mg, often without systematic dose-response testing.

A 2001 study published in Sleep Research Online examined melatonin doses from 0.3mg to 3mg in older adults with insomnia. The researchers found that 0.3mg was as effective as 3mg for advancing sleep onset — doses differed in timing but not in magnitude of effect. A 2012 analysis in Chronobiology International examining multiple melatonin studies found that most sleep-consolidating effects occurred at doses between 0.5-5mg, with no clear evidence that higher doses (5-10mg) outperformed lower ones.

For circadian phase shift — using melatonin to adjust sleep timing during jet lag or shift work — the research suggests 0.5-2mg taken 30-60 minutes before desired sleep time produces meaningful circadian entrainment. Again, doses above this range showed diminishing returns.

The most consistent finding across studies is that melatonin works best when taken at the right time (within the biological window for phase shift, typically 1-2 hours before your natural sleep onset) rather than at a higher dose.

Pharmacokinetics and the Supraphysiological Problem

When you take a 5mg melatonin tablet, plasma concentrations rise to roughly 1000-2000 pg/mL within 30-60 minutes — a 10-fold increase over physiological peak levels. Your body doesn't maintain this supraphysiological concentration; the half-life of melatonin is approximately 20-60 minutes (depending on whether you measure the peripheral or central peak). Within 2-3 hours, levels are back toward baseline.

The question from a physiological standpoint is whether the supraphysiological spike offers any advantage over a dose that more closely mirrors endogenous levels. The research suggests it doesn't, for most applications.

There is a mechanism by which high doses might differ: melatonin has multiple receptor pathways (MT1, MT2, and non-receptor-mediated antioxidant effects). At supraphysiological concentrations, off-target binding might occur. Whether this produces clinically meaningful effects remains unclear, but it opens the possibility of dose-related side effects that lower doses wouldn't produce.

Individual Variation and the Chronotype Factor

Not everyone's pineal gland produces melatonin identically. Genetics influence both the timing and magnitude of melatonin secretion. Some of this variation correlates with chronotype — morning types tend to have earlier melatonin onsets and earlier peak times; evening types have delayed onsets. Some of the variation is simply idiopathic.

Additionally, age matters. Older adults typically produce less melatonin than younger adults, and the onset is often delayed. This is one reason melatonin supplementation is marketed heavily to older populations, even though the evidence for benefit in healthy older adults is mixed.

If your endogenous melatonin production is naturally low, a micro-dose might be sufficient to push you over the threshold needed for sleep initiation. If you're a very late chronotype with already-delayed melatonin onset, timing matters more than dose.

Practical Considerations and Side Effects

The most commonly reported side effects of melatonin at standard doses (5-10mg) are next-day grogginess, vivid or disturbing dreams, and headache. These are not severe, but they suggest that higher-than-necessary doses can produce unwanted effects.

Lower doses (0.5-1mg) produce side effects more rarely, though individual sensitivity varies. If you're considering melatonin, a reasonable experimental approach is to start with the lowest available dose — 0.5mg if you can find it, or a fraction of a standard tablet — and use it consistently for 2-3 weeks before assessing whether it shifts your sleep timing or quality.

The timing of intake matters as much as the dose. Taking melatonin at the wrong circadian window (for instance, right at bedtime when you're already drowsy) produces less circadian effect than taking it 30-90 minutes before your target sleep time. The circadian-phase-shifting effect is the mechanism most supported by research; the "knock you out" effect at high doses is less specific and less reliable.

The Bottom Line

Standard melatonin supplements (5-10mg) contain 15 to 50 times the amount your pineal gland produces nightly. Research on dosing suggests that 0.3-1mg is sufficient for most sleep-consolidating and phase-shifting effects, and doses above 3mg don't consistently outperform lower doses.

If you've used melatonin at standard doses without much benefit, trying a micro-dose (0.5-1mg) at the right circadian timing — 30-90 minutes before your target sleep time — is a logical next step. It may be more effective precisely because it more closely approximates the physiological signal your body is evolved to recognize.