Melatonin is a natural hormone that promotes sleep. It is also available as an over-the-counter (OTC) sleep aid. OTC melatonin lasts for between 2.5 and 10 hours, depending on dosage and other factors.

People who use or are considering using melatonin for sleep may wonder how long it stays in the body.

In this article, we explore what melatonin is, how long it lasts, and how much to take. We also cover potential alternatives to melatonin and its risks and side effects.

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Melatonin is a hormone that regulates the body’s circadian rhythms. The pineal gland produces melatonin. During daytime hours, the retinas in the eyes absorb light, which tells the pineal gland to stop releasing melatonin. As the sun sets, the decrease in light signals melatonin production.

Melatonin acts onTrusted Source regions of the brain that are active when a person is not engaged in a specific mental or physical task. The collective term for these regions is the default mode network (DMN). Melatonin promotes sleep through its effects on the DMN.

Although melatonin is a naturally occurring hormone, it is also available as an OTC sleep aid for people who have difficulty falling asleep or staying asleep through the night.

OTC melatonin may help regulateTrusted Source circadian rhythm disorders in:

  • night shift workers
  • people with jet lag
  • visually impaired people
  • blind people
  • people with dementia

In addition to promoting sleep, melatonin may help relieveTrusted Source anxiety before and after surgery. It may also help treatTrusted Source the following conditions:

  • cancer
  • metabolic disorders
  • cardiovascular disease
  • gastrointestinal (GI) disorders
  • neurodegenerative disorders
  • mental health disorders
  • pain syndromes
  • reproductive issues

The medical community considers melatonin a dietary supplement similar to vitamins and minerals, which the Food and Drug Administration (FDA) do not regulate.

In adults, the typical dose is 0.1–10 milligrams (mg)Trusted Source.

Melatonin has a half-life of about 1–2 hoursTrusted Source, depending on the formulation. A half-life describes the amount of time it takes the body to metabolize half of a dose of medication.

It takes roughly 4–5 half-livesTrusted Source for the body to eliminate a drug. This means that OTC melatonin stays in the body for 4–10 hours, depending on the dose and formulation.

The body absorbs melatonin rapidly. Melatonin levels peak within 1 hourTrusted Source. At this point, a person may begin to feel drowsy.

Everyone metabolizes drugs differently. Some people may feel the effects of melatonin sooner or later than others. The time it takes melatonin to act on the body also depends on its formulation.

Immediate-release melatonin tablets dissolve rapidly, instantly releasing melatonin into the bloodstream. Extended-release melatonin dissolves slowly, gradually releasing melatonin over several hours.

One formulation may work better for some than for others, depending on their particular sleep issues and how their body processes melatonin. Immediate-release melatonin may help people fall asleep shortly after taking it. The extended-release formulation, on the other hand, may help people stay asleep throughout the night.

Many external factors may affect how the body responds to melatonin. These include:

  • age
  • overall health status
  • body composition
  • using other medication
  • tobacco use
  • caffeine intake
  • sleep hygiene

Sleep hygieneTrusted Source refers to habits and environmental factors that promote higher sleep quality. Poor sleep habits, such as exposure to electronics or other sources of bright, artificial light, may tell the brain to stay awake longer.

Melatonin levels peak within 60 minutesTrusted Source, so people should take melatonin 30–60 minutes before they plan to fall asleep.

That said, it is important to remember that melatonin does not affect everyone the same way. People may wish to start taking a low dose of melatonin 30 minutes before they want to fall asleep. They can adjust the timing and dosage, depending on their specific sleep routine.

Generally, it is essential that people do not take melatonin after their ideal bedtime. Doing so can alter their sleep-wake cycle. A person may fall asleep later than they planned or experience daytime fatigue.

Melatonin may help relieve mild or infrequent sleep problems. However, melatonin does carry the risk for mild side effectsTrusted Source, such as:

Melatonin use may also lead toTrusted Source rebound insomnia, dependence, and liver problems.

Although melatonin is a naturally occurring hormone, the FDA do not regulate the quality or dosage of OTC melatonin. This means that some OTC melatonin products may have inaccurate dosage information.

Alternatives to melatonin include natural sleep aids, such as:

However, similar to melatonin and other supplements, natural sleep aids are unregulated. People should only purchase from reputable, high quality manufacturers and distributors.

People who do not want to use OTC melatonin or other sleep aids can try the following sleep hygiene practices:

  • maintaining a consistent sleep schedule by falling asleep and waking up around the same time each day, even on weekends
  • avoiding taking long naps in the evening
  • avoiding using electronics, such as televisions, computers, and cell phones, in the bedroom
  • developing a relaxing and consistent bedtime routine
  • doing relaxing activities, such as reading a book, meditating, or taking a bath, in the evening
  • avoiding eating large meals before bedtime
  • avoiding caffeine in late afternoon or evening
  • exercising during the day
  • keeping the bedroom at a comfortable temperature
  • falling asleep in a dark, quiet room

On average, melatonin takes effect within 30–60 minutes. OTC melatonin can stay in the body for 4–10 hours, depending on the dose and formulation.

People should avoid taking melatonin at or after their intended bedtime. Doing so can shift their sleep-wake cycle and lead to daytime sleepiness.

Practicing good sleep hygiene may help people fall asleep faster and stay asleep throughout the night.

If a person continues experiencing insomnia or other sleep problems, they may wish to contact a doctor to discuss other treatment options.