How Long Does Melatonin Last? Everything You Need to Know

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Dr. Jennifer Hughes, MD

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Imagine this scenario: it’s 3 A.M., and you just can’t get to sleep. 

After hours of frustrating tossing and turning, you remember that little bottle of melatonin rolling around inside your bedside table. 

But first, you hesitate because you aren’t sure how long melatonin lasts in your system—you may be wondering, will I still be groggy when my morning alarm inevitably jolts me awake in just a few short hours?

The short answer is: maybe.

Melatonin has a half-life of 40-60 minutes, and it typically takes five half-lives to clear it fully, meaning it could stay in your body for up to 5 hours.

In this article, learn more about what melatonin actually is, how long melatonin lasts in your system (including different doses), and more frequently asked questions about this little snooze-inducing pill. 

What is Melatonin?

Before we answer how long does melatonin last—what is it, anyway? 

While you’ve probably heard of the over-the-counter sleep supplement, you may not know that our greatest source of melatonin is produced naturally every day in our bodies. 

Melatonin is a hormone produced by the pineal gland, a tiny organ shaped like a miniature pinecone—that’s where it gets its name—located in the deep center of your brain. 

The pineal gland doesn’t have too much to do during the daylight hours, but when nighttime comes around, it gets to work. 

As described in a review in the journal Current Neuropharmacology, the body needs the amino acid tryptophan to create melatonin—this is why people (erroneously) claim that Thanksgiving turkey puts them to sleep. 

Tryptophan then gets converted into a compound called 5-HTP (5-hydroxytryptophan), followed by a transformation into the “happy hormone” serotonin, the direct precursor to melatonin. 

What Does Melatonin Do?

However, this conversion and synthesis of melatonin doesn’t happen all day, every day.

Darkness stimulates the pineal gland to produce melatonin—for people on a typical sleeping schedule (from about 10 or 11 P.M. to 7 A.M.), this is around 9 P.M.—to nudge you with a feeling of sleepiness. 

Nighttime melatonin levels are about ten times greater than in the morning, preparing your body for sleep by lowering blood pressure, body temperature, and the stress hormone cortisol. 

Conversely, in the morning, your retina sends a signal to a center in the brain’s hypothalamus called the suprachiasmatic nuclei (SCN) when light first hits your eyes.

This tells the pineal gland to shut down melatonin production and perform wake-up duties instead, like raising body temperature and releasing some cortisol to get you going on your day. 

​​The timing of our sleep-wake cycles—and melatonin synthesis— is governed by the circadian rhythm, our body’s 24-hour internal clock. 

Circadian rhythm is controlled by light exposure, as various wavelengths of light alter melatonin production, and the SCN is responsible for keeping the circadian rhythm’s pace. 

Disruptions to Melatonin Production

So, ideally, melatonin is only produced after sundown and is halted during the day.

But, there are many disrupters to our biology.

The most significant obstruction of melatonin synthesis is our constant use of artificial lights and various electronic screens after dark.

Whereas our ancestors used to wake and sleep with the sun and moon (with maybe just a fire here or there at night), our modern lifestyles bombard our systems with bright lights at all hours.

Leading these incessantly bright lives can significantly diminish natural melatonin production, making it hard to get to sleep.

Other ways we disrupt our melatonin production include: 

  • Jet lag or travel across time zones
  • Working night shifts 
  • High stress levels 
  • Exercising too close to bedtime
  • Excessive caffeine consumption

How Long Does Melatonin Take To Work?

Naturally produced melatonin starts to rise about two hours before bed.

This is usually around 9 P.M.—unless your eyes are glued to a screen, then melatonin is delayed until you hit the “off” switch.

As a supplement, differing forms of melatonin will be absorbed at different rates.

It’s estimated that melatonin pills start to kick in anywhere from 20 minutes to 2 hours after taking it.

Most melatonin supplements will take about 30 to 60 minutes to work, with typical doses ranging from 3mg to 5mg.

But, as we all have different metabolisms, it may take some trial and error to find the right time to take your melatonin. 

How Long Does Melatonin Last in Your System?

Melatonin has a half-life of about 40 to 60 minutes—meaning it will take that long for your body to metabolize half of the dose you took.

Typically, it takes five half-lives for you to entirely eliminate a melatonin supplement, meaning it will stay in your body for up to 5 hours.

However, this can vary widely, depending on age, body weight, the dosage, the type of supplement you took (like immediate vs. quick-release), and other medications you may be on.

Because of these factors, some people’s late-night melatonin pills won’t fully wear off until 8 hours later.

As you can see, there is no “one size fits all” answer for how long melatonin lasts in your system. 

How Long Does 5mg Melatonin Last?

If you took a 5mg melatonin supplement, you could expect your body to break down 2.5mg of it within the first hour and 1.25mg by hour two.

With a typical half-life of 40 to 60 minutes, you’ve likely cleared 5mg of melatonin from your system by hour five or six. 

How Long Does 3mg Melatonin Last?

A smaller dose of 3mg of melatonin will get metabolized faster than a larger dose. 

In the first hour—or even as little as 40 minutes—you’ll already be down to 1.5 mg in your system. 

Therefore, 3mg of melatonin will likely last in your system for about four hours or less

Does Melatonin Really Help With Sleep?

Most studies that find a positive relationship between melatonin supplementation and sleeping better involve people with sleep conditions, like insomnia or jet lag, and those who work night shifts.

We don’t have as much research on generally healthy people who take melatonin sporadically, but many will anecdotally report that melatonin helps their sleep. 

Melatonin and Jet Lag 

If you’re a frequent jetsetter, you’re likely aware of the unpleasant feelings that arise from flying across multiple time zones.

Jet lag throws your circadian rhythm for a loop—and it can take some time to reset that rhythm. 

Some research has found that melatonin supplementation can help with jet lag symptoms, including this review from the Cochrane Library (a.k.a. the best of the best when it comes to evidence-based review articles).

The research team compiled and analyzed results from ten trials, finding that melatonin was “remarkably effective” at preventing or reducing jet lag symptoms in 9 out of 10 studies, especially with flights crossing five or more time zones.

Melatonin’s efficacy was enhanced when taking it close to the target destination bedtime—especially when flying east—and 5mg was the ideal dose reported

Melatonin and Shift Work

Melatonin has also exhibited positive effects for shift workers, including those working graveyard hours or medical professionals that work overnight shifts.

Another Cochrane review found that melatonin supplementation after a night shift moderately increased sleep length by an average of 24 minutes.

However, the quality of evidence was low, and many other studies of melatonin in shift workers have reported inconclusive results. 

Melatonin and Insomnia

If you struggle with insomnia, you’ve likely tried every trick in the book to fall asleep and stay asleep.

Unfortunately, melatonin might not be one of those one-size-fits-all answers.

Research has been relatively inconclusive when it comes to melatonin helping insomniacs, although many people anecdotally report a benefit. 

One study published in the journal Sleep Medicine Reviews compiled data from 12 studies on melatonin and insomnia.

The most robust evidence supported the use of melatonin in reducing sleep onset latency—how long it takes to fall asleep—in people with insomnia or delayed sleep phase syndrome (a.k.a. “night owls”). 

So, although it doesn’t work for everyone, many people with insomnia find that melatonin supplements help them fall asleep faster. 

FAQs About Melatonin Supplements 

Now, let’s take a look at some other frequently asked questions about melatonin supplements. 

How Much Melatonin Should I Take?

Most studies on melatonin use doses ranging from 1 to 5mg.

High doses of melatonin are not typically recommended, and many professionals suggest starting at the lower dosage of 1 mg and gradually increasing if needed.

Many people find sleep success with a 3mg dose.

When using melatonin for jet lag, the dose with the best-reported effectiveness is 5mg. 

If you find yourself waking up groggy or very sleepy the next day, your dose is likely too high, and you should reduce it the next time.

Also, taking too much melatonin can have the opposite effect, making it harder to sleep because your normal circadian rhythms are disrupted. 

When Should I Take Melatonin?

For most people, the best time to take melatonin is one hour before your desired bedtime.

Your body starts to ramp up its natural melatonin production one to two hours before bed, so melatonin supplementation can help to support this process. 

Can You Overdose on Melatonin?

Although melatonin is generally considered safe, it is possible to take too much of the sleep hormone.

So, the short answer is yes; you can overdose on melatonin.

A melatonin overdose ​​can cause extreme drowsiness, nightmares or vivid dreams, headaches, nausea, dizziness, anxiety, diarrhea, joint pain, and changes in blood pressure. 

There is no official recommended melatonin dosage, as people’s sensitivities and reactions to it can vary widely.

However, at 5mg or less, melatonin is likely safe and well-tolerated for most adults.

FYI: Young children should avoid melatonin unless otherwise directed by a doctor, as melatonin overdoses in kids are on the rise.

Is it Bad to Take Melatonin Every Night?

According to the National Center for Complementary and Integrative Health, taking melatonin in the short term appears to be safe for most adults.

However, we don’t really know yet how long-term melatonin supplementation affects health. 

Fortunately, melatonin is not addictive, habit-forming, or likely to cause dependency issues.

However, some sleep researchers believe that taking melatonin habitually can lead to your body not producing as much melatonin naturally, which can be detrimental to your sleep if you don’t continually take it. 

As a Johns Hopkins sleep expert, Luis F. Buenaver, Ph.D., C.B.S.M., states, “If melatonin does seem to help, it’s safe for most people to take nightly for one to two months.”

After that, it’s recommended to take a short break before using melatonin again. 

Can I Take Other Sleep Supplements With Melatonin? 

Many sleep supplements combine several snooze-supporting compounds alongside melatonin, including L-theanine, vitamin B6, magnesium, or GABA, one of our body’s calming neurotransmitters.

While you should never take melatonin with prescription sleep aids (sleeping pills), these natural compounds are considered safe additions. 

These compounds support sleep in various ways, including calming muscles and nerves, promoting a state of relaxation in the brain, and reducing anxious thoughts.

Products like Som Sleep—a low-calorie nighttime drink containing 3mg of melatonin, vitamin B6, magnesium, L-theanine, and GABA—combine multiple ingredients to support a good night’s sleep.

Melatonin: The Fine Print

Melatonin supplements are not recommended for infants and young children, people who are pregnant or breastfeeding, and those with some autoimmune diseases, seizure disorders, or depression.

People with dementia may also have increased sensitivity to melatonin.

You may want to talk with your doctor if you have high blood pressure or diabetes because melatonin may alter these conditions. 

Key Takeaways

  • Melatonin is a commonly used sleep supplement, with research supporting its benefits in people with jet lag, insomnia, and shift workers. 
  • Melatonin has a half-life of 40 to 60 minutes; most people will metabolize a typical dose (3mg to 5mg) of melatonin within five to six hours. 
  • Melatonin is generally recognized as a safe sleep supplement to take in the short term, but we don’t have evidence yet of long-term health effects. 
  • It’s recommended not to take melatonin habitually for more than one or two months at a time.  

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