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?

These supplements contain natural or synthetic versions of melatonin, a hormone that our bodies produce to regulate the sleep cycle. "Melatonin is a hormone that's naturally produced in the brain in response to darkness and helps to regulate the circadian rhythm and tells the body that it's time to sleep, hence its nickname, 'the hormone of darkness,'" explains Nishi Bhopal, M.D., a psychiatrist specializing in sleep medicine.

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.

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.

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.

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.

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.