Melatonin
The darkness hormone that tells your body when to sleep
Plain English
Melatonin is a hormone produced by the pineal gland in the brain as light fades in the evening. It does not knock you out like a sedative; it shifts your body toward a sleep-ready state by lowering alertness, reducing core body temperature, and signaling that night has arrived. Levels typically rise around 9-10pm, peak near 2-3am, and fall toward waking.
The Mechanism
Melatonin production is controlled by your brain's master clock, the suprachiasmatic nucleus (SCN), which sits in the hypothalamus. During the day, light signals from the eyes tell the SCN to suppress melatonin production. As light fades in the evening, the SCN lifts that suppression and the pineal gland begins releasing melatonin into the bloodstream. This release typically occurs about 2 hours before your natural sleep window and is one of the most reliable markers of your internal clock time.
Melatonin is not a sedative. Its role is timing, not sedation: it tells your body that night has arrived and coordinates the downstream changes that prepare you for sleep. Core body temperature begins to drop, alertness falls, and the systems that support wakefulness start to quiet. Sleep itself happens because of rising sleep pressure (adenosine buildup), not because of melatonin directly. This is why melatonin supplementation at the wrong time or in too-high a dose often fails to improve sleep quality: it can shift the clock, but it cannot force sleep when sleep pressure is low.
Artificial light at night, particularly the short-wavelength light from phones, tablets, and overhead LED lighting, is the primary modern suppressor of melatonin. Even moderate indoor light exposure in the 2 hours before bed can delay melatonin onset by 90 minutes or more (Gooley et al., 2011, Journal of Clinical Endocrinology and Metabolism). This is the mechanism behind why evening screen use delays sleep onset and reduces total sleep time: it is not stimulation from content, it is a direct hormonal disruption.
Why It Matters
Melatonin is a timing signal, not a sleep drug. Protecting it is more powerful than supplementing it.
A well-timed melatonin rise anchors your circadian rhythm and ensures that sleep pressure and biological night align. When artificial light delays melatonin onset, your body clock shifts later while your alarm stays fixed, producing a form of chronic partial sleep deprivation. Low-dose melatonin (0.5-1mg) taken 30-60 minutes before your target bedtime is one of the few supplements with strong evidence for shifting the sleep window, particularly for jet lag, shift work, and delayed sleep phase. It does not improve sleep quality in people who already fall asleep at the right time; it is a clock signal, not a sedative.
Common Misconception
Most people take far too much melatonin. The standard over-the-counter dose in the United States is 5-10mg, but the dose needed to shift the circadian clock is 0.3-1mg. Higher doses do not produce better or faster sleep; they produce longer half-life, morning grogginess, and potential blunting of the body's own melatonin production over time. The pharmacological dose that most people take is 5-30x higher than the physiological dose that actually works.
Signs It Is Disrupted
- Difficulty falling asleep despite feeling physically tired.
- Sleep timing that drifts progressively later each night without intervention.
- Waking earlier than desired and being unable to return to sleep (possible low melatonin in early morning).
- Seasonal mood and energy changes that worsen in winter months with shorter days.
- Jet lag that takes longer than expected to resolve.
- Chronically falling asleep past midnight despite wanting to sleep earlier.
How to Improve It
3 Things to Remember
Melatonin is a timing hormone, not a sedative: it signals that night has arrived and coordinates the body's shift toward sleep, but sleep itself is driven by adenosine buildup, not melatonin levels.
Artificial evening light suppresses melatonin production, often delaying onset by 90 minutes or more, which is the direct mechanism behind why late-night screen use pushes sleep timing later.
Low-dose melatonin (0.5-1mg) is effective for shifting the sleep window; the standard 5-10mg doses sold in most stores are 5-30x higher than the dose that works and increase the risk of morning grogginess.
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