Melatonin onset, often referenced clinically as dim light melatonin onset or DLMO, is the point in the evening when the pineal gland begins releasing melatonin in measurable amounts, usually about 2 hours before habitual sleep onset. It is the cleanest marker of where the internal night begins for a given person.
Why it matters for timing
DLMO is the reference point that makes evening dose windows interpretable. A compound taken before DLMO sits in a wake-leaning phase, while a compound taken after DLMO sits in the wind-down phase the body has already begun.
What shifts the onset later
- Bright light in the evening, especially blue-rich screen light at the eyes.
- Late high-intensity training that elevates core body temperature.
- Late caffeine that persists into the wind-down window.
- An evening-shifted chronotype for which DLMO is naturally later.
What shifts the onset earlier
- Bright morning light at the eyes, ideally within an hour of waking.
- A consistent wake time held within 30 to 60 minutes most days.
- Low-dose melatonin has been used in circadian-shift contexts to move DLMO modestly earlier, with response varying by person.
Field-level operating notes
For logging, DLMO is often estimated as roughly 2 hours before habitual lights-out unless a formal saliva assay is available. Sleep-active supplements can then be reviewed against that estimate, and bright evening light should be logged as a confounder. A higher melatonin dose at the wrong time can make the onset less predictable, not more.
Cross-site references
Uncertainty
- Evidence is limited on how precisely consumer-dose melatonin shifts DLMO across users.
- Evidence is limited on the best methods to estimate DLMO without a saliva test.
How this appears in Unfair
Unfair estimates a working DLMO from your reported sleep time and uses it to place sleep-tagged compounds inside the wind-down window rather than at a fixed clock hour.
Clinical safety note
Pregnancy, autoimmune disease, seizure disorders, and many psychiatric medications change the safety picture for melatonin. Confirm with a clinician before adding it to a routine.