How Long Does Melatonin Last in Your System?

Medically reviewed by
 Dr. David Gao, PharmD., MBA

Dr. David Gao, PharmD., MBA

Dr. David Gao, PharmD., MBA is a licensed pharmacist specializing in oncology and nutrition. He earned his Doctorate of Pharmacy at St. John’s University and completed his Masters of business…

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By McKenzie Hyde Certified Sleep Coach

Melatonin is a naturally occurring hormone that helps regulate our sleep-wake cycle or circadian rhythm. Its release is regulated by sunlight. When we are exposed to more light during the…

Last Updated On May 17th, 2021
How Long Does Melatonin Last in Your System?

Melatonin is a naturally occurring hormone that helps regulate our sleep-wake cycle or circadian rhythm. Its release is regulated by sunlight. When we are exposed to more light during the day, melatonin remains low, and we stay active and alert. However, in the evening, when light decreases, melatonin increases, and we begin to feel sleepy.

Today, melatonin supplements are used as a sleep aid for insomnia and other sleep disorders. (Though, they’re not something we’d recommend.)

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Melatonin supplements are also commonly used by those with circadian rhythm disorders, such as shift workers required to sleep at odd hours and those suffering from jet lag. But, many people may not understand how long melatonin can last in the body (and how it can impact our natural circadian rhythms).

To help, we answer this question and explain how melatonin affects sleep.

How Does Melatonin Work?

The pineal gland, located in the middle of the brain, produces melatonin. The suprachiasmatic nucleus (SCN), a group of nerve cells in the hypothalamus, controls the pineal gland through signals that regulate our internal clock.

When the retina absorbs light, it sends a signal to the SCN. The SCN then communicates with the pineal gland to stop melatonin production. In the absence of light, the SCN stimulates the pineal gland and triggers the release of melatonin.

When melatonin levels are high, our body temperature and blood pressure drop. At the same time, the SCN slows down neuronal activity in the brain, helping us prepare for sleep.

How Long Until Melatonin Works?

Melatonin supplements affect each person differently. While one person may become sleepy within 1 hour of taking the supplement, others may feel tired after 10 to 15 minutes. However, melatonin is quickly absorbed by the body, so most people feel the full effect within the first hour.

Most melatonin supplements are released into the bloodstream immediately after taking them. However, some formulations are designed for extended-release. This means small amounts of melatonin enter the bloodstream over time. Time-released melatonin is intended to mimic the body’s natural production of melatonin, which occurs throughout the night.

How Long Does Melatonin Stay in Your Body?

In general, melatonin doesn’t stay in the body for long. The half-time of the supplement, the time it takes for your body to metabolize half of the dosage, is about 30 to 40 minutes. In most cases, it takes 4 to 5 half-lives for your body to eliminate the supplement. Therefore, melatonin can stay in your body for up to 4 hours.

For this reason, we recommend you avoid driving or operating dangerous equipment at least 5 hours after taking the supplement. However, because melatonin affects each person differently, it may take longer for it to clear your system. The following factors could affect how long melatonin remains in your body.

  • Age: Early research shows that melatonin may stay active for longer periods of time in older individuals.
  • Caffeine intake: Caffeine is a stimulant that may counter the effects of melatonin.
  • Body weight: Heavier individuals (those over 250 pounds) may not feel the effects of a small dosage of melatonin.
  • You are taking other medications: Blood pressure, hypertension, immunosuppressant, and diabetes medications, as well as blood thinners and other anticoagulants, may change the way your body processes supplemental melatonin.

How Much Melatonin Should You Take?

The United States Food and Drug Administration (FDA) classifies melatonin as a dietary supplement, similar to vitamins and minerals. This classification means that melatonin is not regulated in the same way prescription or over-the-counter medications are. Therefore, there are no safe dosage guidelines for melatonin, making it difficult to determine the right amount to take.

Additionally, melatonin affects each person differently. A low dose of melatonin (0.5 mg) may cause extreme sleepiness in one person and have no effect on another. There is also conflicting evidence on whether or not this supplement is safe for pregnant women or young children.

“Melatonin supplements are available in a wide range of doses. Doses can be as low as 0.3 milligrams to as high as 10 milligrams. Additionally, melatonin supplements are available in a variety of formulations. Examples include oral capsules or tablets, sublingual liquid or sprays, topical creams or drops, and intravenous preparations. Moreover, melatonin is available in different release forms such as immediate, extended, and timed release. The duration and elimination of melatonin depends on all of these factors as well as individual demographics and metabolism,” says Dr. David Gao of Memorial Sloan Kettering Cancer Center.

Due to these risks, we suggest avoiding melatonin use altogether and, instead, try to increase your melatonin levels naturally through diet, exercise, and light exposure.

Frequently Asked Questions

What are the side effects of melatonin?

Many people use melatonin pills to fall asleep at their desired bedtime and maintain a consistent sleep-wake cycle. However, too much melatonin in the body can actually make it harder to fall asleep and cause frequent nighttime disruptions. Plus, since there are no safe dosing guidelines, it can be difficult to determine the correct dose of melatonin.

The following are side effects of taking too much melatonin Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source :

  • Sleep loss
  • Headache
  • Nausea
  • Anxiety and depression
  • Diarrhea
  • Joint pain
  • Seizures
  • Dizziness
  • Abdominal pain
  • Mild tremors

Will taking melatonin cause my body to stop producing it?

There is no evidence to suggest that taking a melatonin supplement will cause your body to stop producing the hormone naturally. However, when caffeine is combined with melatonin, it may inhibit the body’s natural ability to produce this hormone.

What foods are rich in melatonin?

How Long Does Melatonin Last

There are several foods rich in melatonin and can help you get to sleep naturally. Fruits and vegetables such as cherries, spinach, tomatoes, and bananas contain melatonin. Other foods, such as honey, turkey, sweet potatoes, oats, and almonds, encourage natural melatonin production. Any of these foods can make a healthy bedtime snack.

Can melatonin cause nightmares?

While some evidence suggests that melatonin can decrease REM sleep disorders, such as sleepwalking and night terrors, other studies Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source suggest that high melatonin levels may cause lucid dreaming.

Vivid dreams when taking melatonin are often caused by high levels of vasotocin in the brain. Vasotocin is produced by melatonin and is responsible for erasing memories while you dream. Too much melatonin in the body could lead to prolonged periods of memory-erasing sleep, which causes vivid dreams. Lucid dreams can often lead to daytime sleepiness and grogginess.

Is melatonin bad for your liver?

Although melatonin was thought to cause serum enzyme elevation in the liver, current research Verified Source National Library of Medicine (NIH) World’s largest medical library, making biomedical data and information more accessible. View source shows that melatonin was not associated with this change or any other cases of liver injury. However, if you have experienced liver complications in the past, it is best to seek medical advice before taking melatonin supplements.


In general, melatonin remains in the body between 4 and 5 hours. However, due to unregulated dosing guidelines, many people may not understand exactly how much melatonin they should take. This can lead to overconsumption of the supplement and a melatonin overdose, with dangerous side effects. Before you begin taking melatonin, we suggest discussing it with your doctor first.

About the author

McKenzie Hyde is a Certified Sleep Science Coach and a full-time writer focused on sleep health and the mattress industry. She currently writes articles on a variety of topics, ranging from sleep hygiene to the newest trends in the mattress and bedding industry. Just some of the topics she has covered include best sleep practices for students, the consequences of going without sleep, and choosing the right bed if you suffer from back pain. McKenzie Hyde holds a Master of Arts degree from Utah State University where she studied literature and writing. While there, she taught argumentative writing and wrote a variety of articles and analyses for literary and academic journals.

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