Unlike gentler sleep aids, melatonin supplements tend to make their presence known. That is, most people feel quite tired after taking them at bedtime, and they might feel some lingering sleepiness when they wake up too. This raises the question: How long does melatonin actually stay in the body, and what does that mean for how it should be consumed?

We asked sleep and health experts all about the life span of melatonin, and how it should (and should not) be used. Here's what to know.

There's nothing more frustrating than lying awake, willing sleep to come. Seema Bonney, M.D., the founder and medical director of the Anti-Aging & Longevity Center of Philadelphia, notes that melatonin has become a popular tool over the last 20 years among those looking to fall asleep. According to a recent research letter in the Journal of the American Medical Association1, consumption of melatonin supplements has "significantly increased" across every U.S. demographic surveyed since 1999.

Bonney notes that the average person's melatonin levels will start to rise after sunset (assuming limited inputs from other light sources) and peak around 2 a.m. to 4 a.m. If, for some reason, you are trying to fall asleep outside of your peak melatonin window (say, if you're traveling to a new time zone or working during daylight hours), taking supplemental melatonin tells your body that it's time for bed, despite what your environmental cues are saying.

"For adults, melatonin works by changing the timing of our 24-hour circadian rhythm. This is helpful if we are shift workers, our circadian rhythm is out of time with our regular work or school hours, or we wish to minimize travel fatigue," says Michael Gradisar, Ph.D., a clinical psychologist and sleep specialist with Sleep Cycle.

Melatonin supplements contain anywhere from 0.5 to 10 milligrams of the hormone. "People often think the more I take, the more effective melatonin will be," Gradisar observes. Indeed, the Journal of the American Medical Association found that taking more than 5 milligrams of melatonin per day has become more common in this country in the last two decades.

However, both Bonney and Bhopal generally recommend sticking to a lower dose. "[I say] 'less is more' when it comes to melatonin, and typically recommend doses of one milligram or less, usually closer to 0.5," says Bhopal.

"In fact, per the science, the physiological melatonin dose—what's in our body under normal circumstances—is only around 0.3 to 0.5 milligrams," explains Ashley Jordan Ferira, Ph.D., RDN, mbg's vice president of scientific affairs. "Put in that important context, people are megadosing on melatonin these days. It's concerning," she goes onto say.

And she's not alone in her cautionary posture. "It's important to remember that melatonin is a hormone, and using any hormone regularly can down-regulate your own production of that hormone," notes Bonney. This is one reason it's best to avoid taking high doses of melatonin—especially on a regular basis. Furthermore, "melatonin has the ability to impact other hormones, like estrogen and testosterone2," Ferira adds.

There is also no scientific evidence to suggest that melatonin will be more effective at doses higher than 3 milligrams. "There are, of course, a limited number of specific clinical or research situations, where concentrated doses of melatonin may be indicated by a licensed healthcare provider," Ferira caveats. "That's not what we're talking about here," she expounds.

Taking melatonin supplements in higher doses also increases your chances for side effects like headaches, nausea, dizziness, and daytime sleepiness, Bonney adds.

You'll find two types of melatonin supplements on shelves: slow-release (aka time or extended release) and fast-release. Depending on the formula, Bonney notes that it will take anywhere between 30 minutes and two hours to kick in. And the impact of the former (sustained release) products "can linger longer than you might want, messing with normal melatonin homeostasis," adds Ferira.

"Timing is key with melatonin, as taking it at the incorrect time can throw off the circadian rhythm," Bhopal cautions. "Generally, most people benefit from taking it about 30 minutes before their target bedtime. However, if melatonin is being used to shift the circadian rhythm, then it may be used strategically at different times."

Gradisar says that if someone is looking to push their bedtime up, for example, they might take melatonin a little bit earlier every night until they feel tired at the target hour.

However, be sure to consult your doctor before attempting a shift like this. "It's important to keep in mind that melatonin is a hormone and should be used intentionally, ideally under the guidance of a licensed health professional," Bhopal says.

The half-life (the time it takes for the body to metabolize half a dose) of melatonin is approximately 20 to 50 minutes, says Bonney. "On average, it takes four to five half-lives for the body to fully eliminate a melatonin supplement," she adds, meaning this type of melatonin will stay in your system for anywhere from four (fast-release) to eight (slow-release) hours.

However, Bhopal notes that it isn't uncommon to feel the lingering effects of melatonin (fogginess, fatigue) after this time window is up. For this reason, it's important to pay attention to how melatonin affects you personally and how you feel after taking it.

While melatonin can be effective for shifting the circadian rhythm to help people fall asleep within a new time window, the experts interviewed for this piece agree that it's not meant to be taken as a nightly sleep supplement. "It's more of a body clock regulator than a sleep aid," Bhopal notes. "For temporary reset support, sure, but daily melatonin use is not something I would recommend," echoes Ferira.

If nightly sleep support is what you're after, they recommend first cleaning up your sleep hygiene routine. For starters, being strategic about the timing of your light exposure is key.

In the hours leading up to bed, "avoiding devices and the blue light they emit is essential for optimizing your sleep hygiene since blue light disrupts melatonin production," says Bonney. "Turn off bright overhead lights in favor of dim lamps since darkness is your body's cue to increase melatonin production. Remember, you have photoreceptors all over your body, so eliminating light as much as possible is helpful."

Bhopal adds that once you've dimmed the lights and put away electronics, you'll want to wait to get into bed until you actually feel sleepy. "Staying in bed while you're awake trains your brain to associate the bed with wakefulness," she explains.

"Honor your wind-down ritual and be super picky about light, noise polluters, and temperature. That might mean earplugs, a noise machine, or fan depending on your specific situation," adds Ferira.

Those who are looking to not only fall asleep faster but stay asleep longer and reach more restorative stages of rest can also look into sleep supplements that utilize nonhormonal ingredients like magnesium, L-theanine, and relaxing botanicals or bioactives or herbs.*

Melatonin is one of the most popular sleep supplements available, but it's important to use it with caution. Increasing levels of melatonin in the body for four to eight hours at a time can be helpful in isolated situations, but for sustained nightly sleep support, you're better off going with another option.