Melatonin and Sleep: How It Works, Dosage, and Side Effects

Melatonin is often called the "sleep hormone," but it does not actually make you sleep. Produced by the pineal gland in response to darkness, melatonin serves as a biological signal that tells your body night has arrived and it is time to prepare for rest. This guide covers how melatonin works, how much to take, when to take it, and what the research says about supplements, side effects, and natural alternatives.

What Is Melatonin?

Melatonin (N-acetyl-5-methoxytryptamine) is a hormone produced primarily by the pineal gland, a pea-sized structure deep in the center of your brain. Unlike hormones that are regulated by other glands, melatonin production is controlled almost entirely by light and darkness detected by your eyes. According to the Sleep Foundation, melatonin serves as your body's internal timekeeper, signaling when darkness arrives and sleep should begin.

The synthesis pathway begins with the amino acid tryptophan, which your body obtains from food. Tryptophan is converted to serotonin during the day, and then when darkness falls, an enzyme called AANAT (arylalkylamine N-acetyltransferase) converts serotonin into melatonin. This process is why serotonin levels tend to be higher during the day and melatonin levels rise at night — they share the same precursor molecule.

A critical concept in melatonin science is dim light melatonin onset (DLMO). This is the point in the evening when melatonin begins to rise, typically about 2 hours before your habitual bedtime. DLMO is considered the most reliable marker of your circadian rhythm timing and is used in clinical sleep research to determine whether someone's internal clock is properly aligned. According to a comprehensive review published in the Journal of Clinical Endocrinology & Metabolism, DLMO typically occurs between 8:00 and 10:00 PM for adults on conventional schedules.

How Melatonin Regulates Your Sleep-Wake Cycle

Your sleep-wake cycle is governed by the suprachiasmatic nucleus (SCN), a tiny cluster of about 20,000 neurons in the hypothalamus. Often called the "master clock," the SCN receives direct light input from specialized cells in the retina called intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells are particularly sensitive to blue light wavelengths around 480nm. Research from the National Institutes of Health has mapped exactly how this light-brain pathway controls your internal clock.

When light hits these cells during the day, the SCN suppresses melatonin production, keeping you alert. As evening approaches and light levels drop, the SCN signals the pineal gland to begin releasing melatonin. This is why melatonin is sometimes called the "hormone of darkness" — it does not cause sleep directly but opens what researchers call the "sleep gate," a window during which your body is physiologically prepared for sleep.

The National Sleep Foundation explains that melatonin lowers core body temperature, reduces alertness, and promotes a state of quiet wakefulness that precedes sleep. If you fight this window by staying up with bright lights or screens, you push your melatonin onset later, effectively telling your brain it is still daytime. Use our bedtime calculator to find the optimal time to start winding down based on your required wake time.

Melatonin Levels Across 24 Hours

The chart below shows how melatonin concentration changes throughout a typical day for someone sleeping from 10:30 PM to 6:30 AM. Levels are measured in picograms per milliliter (pg/mL) of blood plasma.

DLMO = Dim Light Melatonin Onset. Purple bars indicate rising/elevated melatonin; dark blue bars indicate peak nocturnal levels. Values are approximate for a healthy young adult.

The Science of Melatonin Synthesis

Understanding how your body creates melatonin helps explain why certain supplements, foods, and lifestyle factors affect sleep. The NIH's StatPearls provides detailed biochemistry of this four-step pathway:

Factors That Affect Melatonin Synthesis

Learn more about caffeine's effects in our caffeine and sleep guide.

Natural Melatonin Production by Age

One of the most significant findings in melatonin research is that natural production decreases substantially with age. According to the Cleveland Clinic, infants produce very little melatonin in the first few months, production peaks in childhood, and then gradually declines throughout adulthood. By age 70, many people produce only a fraction of what they produced at age 10. This decline may partially explain why older adults often have difficulty falling and staying asleep.

Melatonin Production Decline by Decade

Use our sleep by age calculator to check how much sleep is recommended for your specific age group and adjust your bedtime accordingly.

Melatonin Supplements: Dosage Guide

The melatonin supplement market has grown into a multi-billion-dollar industry, but there is a fundamental disconnect between what research supports and what most products contain. Your body naturally produces about 0.1 to 0.3mg of melatonin per night. Yet the most popular supplements contain 5 to 10mg — roughly 30 to 100 times the physiological amount.

A landmark study from Harvard Medical School researcher Dr. Richard Wurtman found that doses as low as 0.3mg were effective for improving sleep, while higher doses (3mg+) often caused plasma melatonin levels to remain elevated into the next day, leading to daytime grogginess. The National Center for Complementary and Integrative Health (NCCIH) notes that melatonin supplements are "possibly effective" for sleep, but that more is not better.

Clinical Effectiveness Research

What does the research actually say about melatonin's effectiveness? The American Academy of Sleep Medicine (AASM) has reviewed hundreds of studies to develop evidence-based recommendations. Their findings show that melatonin's effectiveness varies dramatically depending on the sleep problem being treated.

Melatonin Effectiveness by Condition

These modest improvements should be weighed against expectations. If you are looking for dramatic sleep improvements, melatonin alone is unlikely to provide them. The CDC's sleep guidelines emphasize that behavioral changes — consistent schedules, sleep-friendly environments, and proper sleep hygiene — typically produce larger and more sustainable improvements than any supplement.

When to Take Melatonin

The timing of melatonin supplementation is arguably more important than the dose. Taking melatonin at the wrong time can shift your circadian rhythm in the wrong direction, making sleep problems worse. The general principle is: melatonin taken in the evening advances your clock (makes you sleepy earlier), while melatonin taken in the morning delays it (makes you sleepy later).

Optimal Timing Window by Goal

Melatonin Side Effects

Melatonin is generally well-tolerated, especially at lower doses. However, it is not free of side effects, particularly at the high doses found in most commercial supplements. The Mayo Clinic lists the following potential adverse effects.

Side Effect Risk by Dose Level

Melatonin vs Prescription Sleep Aids

Understanding how melatonin compares to other sleep aids helps you make an informed choice. Melatonin works fundamentally differently from sedative medications — it adjusts your circadian clock rather than forcing unconsciousness. Here is how the major categories compare, based on data from the National Institutes of Health and the Sleep Foundation.

Effectiveness Comparison (Sleep Onset Reduction)

Foods That Boost Natural Melatonin

While no food contains melatonin in amounts comparable to supplements, certain foods contain meaningful amounts that may support your natural production, especially when consumed in the evening. Additionally, foods rich in tryptophan (melatonin's precursor) can support the synthesis pathway. Research published on PubMed has documented the melatonin content of various foods.

Relative Melatonin Content in Foods

Note: ng/g = nanograms per gram. For context, a 1mg supplement contains 1,000,000 nanograms, so food sources provide vastly smaller amounts. Their benefit likely comes from supporting the natural synthesis pathway rather than directly raising melatonin levels. For more dietary tips, see our sleep quality tips.

Blue Light and Melatonin Suppression

Of all the factors that affect melatonin production, artificial light exposure — particularly blue light from screens — is the most disruptive and the most controllable. Research from Harvard Medical School found that blue light suppresses melatonin production twice as much as green light and shifts circadian rhythms by twice as much (3 hours vs. 1.5 hours).

A 2014 study published in the Proceedings of the National Academy of Sciences compared people reading an e-book to those reading a printed book before bed. The e-book readers showed suppressed melatonin, delayed sleep onset by an average of 10 minutes, reduced evening sleepiness, and less REM sleep. These effects persisted even after the devices were put away.

Light Source Impact on Melatonin

Strategies to Protect Your Melatonin Production

For a comprehensive look at optimizing your bedroom for sleep, including lighting, temperature, and noise, read our sleep environment tips guide.

Melatonin and Sleep Architecture

Beyond simply helping you fall asleep, melatonin influences the structure of your sleep — the proportion of time spent in each sleep stage. Research from the American Academy of Sleep Medicine shows that exogenous melatonin can affect sleep architecture in complex ways that depend on dose and timing.

Understanding sleep stages is essential for interpreting these effects. Unlike sedative medications that often suppress REM sleep, melatonin appears to preserve or even enhance the natural sleep cycle. Use our sleep cycle calculator to time your sleep for complete cycles.

Special Populations

Certain groups may have unique considerations when it comes to melatonin use. The Cleveland Clinic provides guidance for these special populations:

Melatonin for Children: What Parents Should Know

Melatonin use in children has skyrocketed in recent years, with a 2022 CDC report finding that pediatric melatonin ingestions increased 530% between 2012 and 2021. While melatonin can be helpful for certain pediatric populations, it requires careful consideration.

The American Academy of Pediatrics (AAP) recommends that parents should:

• Try behavioral strategies first — consistent bedtime routine, screen curfew, dark and cool bedroom
• Consult a pediatrician before giving melatonin to any child
• Use the lowest effective dose — typically 0.5mg to 1mg for children, up to 3mg for adolescents with clinical guidance
• Choose quality products — given the labeling inaccuracies found in supplements, select USP-verified products
• Consider it temporary — melatonin should not be a permanent solution for childhood sleep difficulties

Melatonin has the strongest evidence for children with ADHD, autism spectrum disorder (ASD), and delayed sleep phase disorder. A meta-analysis published in the Journal of Child Neurology found that melatonin reduced sleep onset latency by an average of 28 minutes in children with ASD. For neurotypical children with occasional sleep difficulties, behavioral approaches remain the first-line recommendation.

Drug Interactions

Melatonin can interact with numerous medications. The WebMD drug interaction checker and Mayo Clinic identify the following significant interactions:

Frequently Asked Questions

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Related Guides

Medical disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting any supplement, including melatonin. If you have persistent sleep problems, see a board-certified sleep medicine specialist. Information sourced from the NIH, Sleep Foundation, Mayo Clinic, and peer-reviewed research on PubMed.