Why the dose curve is not linear
Melatonin does not follow a simple more-is-better pattern. Doses in the range of roughly 0.3 to 1 mg can produce blood levels close to what the body makes naturally at night, and several researchers have argued that these low, physiological doses are sufficient for the timing and mild sleep-onset effects most people are after. The widely sold 5 to 10 mg tablets push levels far above the natural range without a proportional gain in benefit.
Because melatonin is cleared relatively slowly, high evening doses can leave elevated levels into the morning, which is one proposed reason some users report next-day grogginess or vivid dreams.
Practical reading of the dosing evidence
The figures above describe general patterns from pharmacology and small trials, not a personal prescription. Optimal timing often matters more than amount, and individual response varies. Over-the-counter melatonin potency can also differ from the label, since it is regulated as a supplement in many countries.
This is educational information, not medical advice. Anyone using melatonin regularly, giving it to a child, or combining it with other medication should consult a qualified healthcare professional.