What melatonin does in your body

Melatonin is a hormone your brain makes naturally when it gets dark, signaling to your body that it's time to sleep. The pineal gland, a small structure deep in your brain, releases melatonin in the evening as light fades. This hormone doesn't force you to sleep the way a sedative does—instead, it lowers your core body temperature, reduces alertness, and creates the biological conditions that make sleep easier to fall into.

When you take melatonin as a supplement, you're adding extra of a substance your body already produces. The amount in a typical supplement (0.5 to 10 milligrams) is higher than what circulates naturally, which is why it can shift your sleep timing or deepen drowsiness. Your body breaks it down quickly—most melatonin is metabolized within 30 to 60 minutes—so it doesn't accumulate in your system the way some other sleep aids do.

Key Takeaways

  • Melatonin works by signaling your body that it's time to sleep, not by forcing unconsciousness; it's most effective when taken 30 to 60 minutes before your target bedtime.
  • Human trials show melatonin can reduce the time it takes to fall asleep and may help reset sleep timing after travel or shift work, though the effect is modest for many people.
  • Melatonin appears safe for short-term use in adults, but long-term safety data in humans is limited, and it may interact with blood thinners, diabetes medications, and immunosuppressants.
  • Melatonin is not a treatment for insomnia itself; it works best for circadian rhythm problems (jet lag, shift work) rather than for chronic difficulty staying asleep.
  • Dose, timing, and individual sensitivity vary widely—some people respond to 0.5 mg while others need 5 to 10 mg, and taking it at the wrong time of day can shift your sleep window in the wrong direction.

What human research shows about falling asleep faster

Multiple randomized controlled trials—the gold standard for testing whether a treatment actually works—have found that melatonin can reduce the time it takes to fall asleep. A meta-analysis (a summary of many studies) published in the journal Sleep Medicine Reviews found that people taking melatonin fell asleep about 7 to 8 minutes faster on average than those taking a placebo. That's a real effect, but it's smaller than what many people expect from a sleep aid.

The effect is strongest in people whose sleep timing is shifted—those dealing with jet lag, starting a night shift, or naturally waking very early. In these situations, melatonin can help reset your circadian rhythm (your body's internal 24-hour clock) by signaling sleep at a new time. For people with ordinary insomnia—difficulty falling asleep without an obvious timing problem—the benefit is less consistent. Some studies show modest improvement; others show little difference from placebo.

Timing matters enormously. Taking melatonin 30 to 60 minutes before your target bedtime produces better results than taking it right at bedtime. Taking it too early in the evening can shift your sleep window earlier than you want, while taking it too late may not give it time to work before you're already trying to sleep.

Effects on sleep quality and staying asleep

The research on whether melatonin helps you stay asleep once you've fallen asleep is weaker than the evidence for falling asleep faster. Some studies show modest improvements in total sleep time or fewer nighttime awakenings; others show no difference. This is an important distinction: melatonin appears to work mainly on sleep onset (getting to sleep) rather than sleep maintenance (staying asleep).

If your main problem is waking up in the middle of the night or waking too early and not being able to return to sleep, melatonin alone may not solve it. People with these patterns sometimes benefit more from behavioral approaches—keeping your bedroom cool and dark, avoiding screens before bed, or working with a sleep specialist on cognitive behavioral therapy for insomnia (CBT-I).

Melatonin for jet lag and shift work

This is where the evidence is strongest. Multiple trials show that melatonin can help your body adjust to a new sleep schedule when you cross time zones or switch to night shifts. A review in the Cochrane Database of Systematic Reviews (a rigorous source for medical evidence) concluded that melatonin is effective for reducing jet lag symptoms, particularly when you travel east (which requires falling asleep earlier than your body naturally wants to).

For jet lag, the typical approach is to take melatonin in the evening at your destination for a few nights. For shift work, timing depends on whether you're switching to an earlier or later shift. The key is using melatonin to signal sleep at your new desired time, not at your old one. This is why working with timing is more important than dose—taking the right amount at the wrong time can actually make adjustment harder.

Safety, side effects, and who should avoid it

Short-term melatonin use (a few weeks to a few months) appears safe for most adults. The most common side effects are mild: headache, dizziness, nausea, or grogginess the next morning. Some people report vivid dreams or nightmares. These effects are usually temporary and fade as your body adjusts.

Long-term safety data in humans is limited. Most studies last weeks to a few months, not years. Animal studies have raised questions about whether chronic melatonin use affects reproductive hormones or immune function, but these findings haven't been clearly replicated in humans. If you're considering melatonin for months or years, discuss this with your doctor.

Melatonin can interact with several medications. It may reduce the effectiveness of blood thinners like warfarin, interfere with diabetes medications, or interact with immunosuppressants used after organ transplant. If you take any regular medications, check with your doctor or pharmacist before starting melatonin. Melatonin is also not recommended during pregnancy or while breastfeeding, as safety data is insufficient.

People with autoimmune conditions, seizure disorders, or severe depression should discuss melatonin with their doctor before use, as the hormone can theoretically affect immune function and mood in ways that might complicate these conditions.

Dose and how to use it effectively

There's no single "correct" dose of melatonin—sensitivity varies widely. Some people respond to 0.5 milligrams; others need 5 to 10 milligrams. Starting low (0.5 to 1 mg) and increasing gradually if needed is a reasonable approach. More is not necessarily better; in fact, very high doses (10 mg or more) don't consistently produce better results than moderate doses and may increase the risk of side effects.

Timing is more important than dose. Take melatonin 30 to 60 minutes before your target bedtime. If you're using it for jet lag, take it in the evening at your destination (for eastward travel) or in the morning (for westward travel). For shift work, timing depends on your new schedule.

Melatonin comes in tablets, capsules, gummies, and liquids. Absorption varies slightly by form, but the differences are small. Choose whichever form you find easiest to use consistently. Some formulations are labeled "extended-release," designed to release melatonin gradually over several hours; these may help with staying asleep, though evidence is limited.

When melatonin may not be the right choice

Melatonin works best for circadian rhythm problems—situations where your sleep timing is shifted or misaligned. It's less effective for primary insomnia (chronic difficulty falling or staying asleep without an obvious timing problem). If you've had trouble sleeping for months or years, melatonin alone is unlikely to solve it.

For chronic insomnia, cognitive behavioral therapy for insomnia (CBT-I) has stronger evidence than any medication or supplement. This is a structured approach that addresses the thoughts, behaviors, and habits that maintain poor sleep. Many sleep specialists recommend trying CBT-I before or alongside melatonin.

If your sleep problems are tied to stress, anxiety, pain, or an underlying health condition, treating the root cause is more important than adding melatonin. A doctor or sleep specialist can help identify what's actually disrupting your sleep and recommend the most effective approach.

Frequently Asked Questions

Can I take melatonin every night long-term?

Short-term use (weeks to a few months) is well-studied and appears safe. Long-term nightly use hasn't been thoroughly tested in humans. If you're considering melatonin for months or years, discuss this with your doctor, who can weigh the potential benefits against the limited safety data and monitor for any effects over time.

Will melatonin make me dependent on it?

Melatonin doesn't appear to create physical dependence the way some sleep medications do. However, some people report that their sleep worsens when they stop taking it after using it regularly. This may reflect a return to their baseline sleep pattern rather than true dependence, but it's worth discussing with your doctor if you've used melatonin for a long time.

Is melatonin safe for children?

Melatonin is sometimes used in children with sleep disorders, but evidence is limited and long-term safety is unknown. Children's brains are still developing, and melatonin affects hormones that may influence puberty and growth. Any use in children should be under a pediatrician's guidance, not over-the-counter.

What's the difference between melatonin and prescription sleep medications?

Melatonin is a naturally occurring hormone that works on your circadian rhythm. Prescription sleep medications (like zolpidem or eszopiclone) are sedatives that directly suppress wakefulness. Melatonin is gentler but also less powerful; prescription medications work faster and more reliably for acute insomnia but carry higher risks of dependence and side effects.

Can I take melatonin with alcohol?

Combining melatonin with alcohol is not recommended. Alcohol can interfere with melatonin's effects and may increase drowsiness and impair judgment. Both substances affect your sleep architecture (the structure of your sleep cycles), and combining them can produce unpredictable results.