Melatonin Supplement Response

MTNR1A and MTNR1B code for the two melatonin receptors in the brain and body. The receptors translate circulating melatonin into the actual downstream "sleep signal" — including drowsiness, body temperature drop, and circadian entrainment. Without responsive receptors, even high circulating melatonin produces a muted effect.

Carriers of common MTNR1A and MTNR1B variants are associated with reduced receptor sensitivity — and may find melatonin supplementation produces weaker sleep response than expected. Carriers of high-sensitivity variants are associated with stronger response and often do best at smaller doses (0.3–0.5 mg) than the standard 3–10 mg drugstore options.

Receptor density downregulates with chronic high-dose use, which is why long-term users often experience diminishing returns. Cycling melatonin use (rather than taking it nightly) preserves receptor sensitivity. Timing matters more than dose for circadian shifting — small doses 3–5 hours before desired sleep onset entrain the rhythm; larger doses at bedtime don’t.

The "I tried melatonin and it knocked me out" and "I take 5 mg and feel nothing" experiences aren’t about the supplement; they’re about receptor wiring. Which MTNR variant you carry decides whether to start at 0.3 mg, what timing maximizes effect, and whether the pill is even the right intervention to reach for.