Supplements | Explainer
The Melatonin Dose That Matched the Body's Own Was 0.3 mg. Most Bottles Hold Ten Times That or More.
In studies at MIT, a fraction of a milligram restored normal night time levels. Larger doses kept melatonin raised into the next day. Here is what the research found.
Melatonin is a hormone your body already makes. As light fades, a small gland in the brain releases it into the blood, and the level peaks in the middle of the night before falling away by morning.
The amount involved is tiny. That is the part most people never hear, and it is why the dose on a supplement bottle matters more than it looks.
How much the body makes
Night time blood levels of melatonin are measured in picograms, trillionths of a gram, per millilitre. A typical night time peak is around 60 pg per mL, with a wide normal range, and levels tend to fall with age. Exact values depend on the laboratory test used to measure them.
The first clue: a fraction of a milligram
In 1994, Richard Wurtman's group at MIT gave 20 young men doses of melatonin from 0.1 mg to 10 mg by mouth, in the middle of the day. The 0.1 mg and 0.3 mg doses produced blood levels within the normal night time range. The larger doses went far above it.
The study was published in the Proceedings of the National Academy of Sciences.
The 2001 trial in older adults
In 2001, the same team tested melatonin in 30 people over 50: 15 with insomnia and 15 who slept normally. Each person took a placebo, 0.1 mg, 0.3 mg and 3.0 mg, for a week each.
- 0.3 mg restored sleep efficiency in the poor sleepers and brought blood melatonin back to normal night time levels.
- 3.0 mg also improved sleep, but it lowered body temperature and kept melatonin raised into the daytime.
- Normal sleepers saw no effect from any dose.
Wurtman called 0.3 mg the physiological dose, and said the larger doses sold in stores were less effective. The study was small, and each dose was tested for only a week.
Meanwhile, doses went up
A 2022 study in JAMA tracked melatonin use among 55,021 US adults. Use rose from 0.4% in 1999 and 2000 to 2.1% in 2017 and 2018. Over the same years, the share taking more than 5 mg a day rose from 0.08% in 2005 and 2006 to 0.28%.
And the number on the label may not be what is inside. A 2023 JAMA study found that 22 of 25 melatonin gummies did not match their labels, with actual amounts from 74% to 347% of the stated dose.
What to take from it
More melatonin is not the same as better sleep. The research that matched the body's own levels used doses far below what most shelves carry. If you use melatonin, it is worth asking a doctor or pharmacist about the dose, not just the brand.