Melatonin Dosage: Seven Minutes Faster to Sleep. The Bottles Ranged 83% Under to 478% Over.
Melatonin works. The American Academy of Family Physicians recognises it as first-line pharmacological therapy for insomnia. [1] That is a physician body, not a wellness brand.
It works by about seven minutes. Pooled across trials: roughly seven minutes faster to fall asleep, about eight minutes more sleep in total, and people reported sleeping better. [1]
Both of those sentences are true, and you need both.
Now the part that should change what you buy
Melatonin is not approved by the FDA for any indication. [1] It is sold as a dietary supplement, which is a different regulatory category with different rules about what has to be in the bottle.
Interestingly, the prescription drugs that act on the same receptors — ramelteon, tasimelteon — are FDA-approved for insomnia. [1] The molecule copies are regulated. The hormone itself, on the shelf, is not.
So researchers went and measured what is actually in them.
| What was measured | Result |
| Melatonin vs the label | −83% to +478% |
| Missed the label by over 10% | more than 71% |
| Batch-to-batch, same product | varied up to 465% |
| Contained serotonin | 26% |
Minus 83% to plus 478%
Thirty-one supplements, analysed properly in a laboratory. Melatonin content ranged from 83% below the labelled amount to 478% above it. [2]
More than 71% missed their own label by more than ten per cent. And within a single product, batch to batch, content varied by as much as 465%. [2] Same brand, same box, different bottle, different drug.
The authors add the detail that removes the obvious escape route: the variability “did not appear to be correlated with manufacturer or product type”. [2] You cannot reason your way to a good one by picking a reputable-looking brand.
And a quarter of them contained something else
Eight of the thirty-one contained serotonin, at one to seventy-five micrograms. [2]
The paper’s own summary: melatonin content missed the label in more than 71% of supplements “and an additional 26% were found to contain serotonin”. [2] Serotonin is not supposed to be in a melatonin tablet, and if you have read our methylene blue verdict you already know that serotonin is not a molecule to be casual about in people taking antidepressants.
We are reporting a contamination finding, not a pharmacology claim — how much of one to seventy-five micrograms matters is not something these data answer, and we have not read that literature.
The bit where the reference does our job for us
Usually this site has to draw the line between the product problem and the evidence problem itself. Here the clinical reference draws it.
On why melatonin’s trial results are so inconsistent: “Variable tablet content can make accurate dosing challenging and might contribute to the wide range of efficacy reported in various trials.” [1]
Read that twice. The scatter in the research may be partly a manufacturing problem. Some of those trials were not testing different doses of melatonin so much as testing bottles nobody had measured.
Which also means the seven minutes at the top of this page is an average across an unknown mixture of actual doses. It is the best number available. It is not a precise one.
The verdict
Supported. Melatonin does help people fall asleep, it is endorsed as first-line by a physician body, and it carries a low risk of adverse effects. [1] Among the things this site has checked, that puts it well ahead of most of the shelf.
What is not supported is the number on the front of the box. Across the supplements that have been measured, that number was wrong more often than it was right, wrong by margins that dwarf the differences between the doses people agonise over, and inconsistent between batches of the same product.
So we are not going to tell you how many milligrams to take, and you should be suspicious of anyone who does. The honest version of a dosage answer here is that the dose is not reliably knowable from the label — which is a strange thing to discover about a product recommended as first-line therapy, and the single most useful thing on this page.
If you use melatonin and it helps, that is real and the evidence backs you. If it stopped working when you opened a new bottle, that is also real, and now you know one reason it might.
Journalism, not medical advice. Sleep that will not come for weeks is worth a doctor rather than a supplement aisle — and melatonin for children in particular is a question for a clinician, not a website.
Related: sleep hygiene · methylene blue · how much vitamin D should I take · high cortisol symptoms · every claim we’ve checked
