How Long Does Melatonin Last?

Table of Contents

melatonin sleep setup

Melatonin is a well-known sleep aid that can work quickly to promote sleep. We know the supplement is designed to shorten the length of time it takes to fall asleep, but how long does melatonin last? In some cases, the effects of melatonin can last up to five hours, but the exact time frame depends on factors like dosage, the type of melatonin used, and the person taking it. We spoke with three experts about how long melatonin lasts, plus everything else you need to know about using this popular sleep aid.

What Is Melatonin? 

Melatonin is a hormone that the body naturally produces to regulate our circadian rhythm, explains Dr. Chelsie Rohrsheib, neuroscientist and head sleep expert at Wesper. “When melatonin concentration in the brain is high, it signals to the sleep centers of the brain that it’s time to go to bed,” she says. “When melatonin concentration is low, it signals to the brain to be awake and alert.” 

Dr. Jade Wu, a behavioral sleep medicine specialist and sleep advisor at Mattress Firm, says that natural melatonin production increases in the evenings, peaks during the night, and decreases in the early morning hours. Melatonin supplements are designed to, well, supplement this natural production.

“Taking melatonin in pill form can be used to shift the timing of when you’re sleepy versus awake,” explains Wu. “For example, for people with delayed sleep phase disorder, taking a small dose of melatonin in the early evening can help to ‘nudge’ the timing of their melatonin release earlier. This will help them to feel sleepy earlier in the evening and awake earlier in the morning.”

How Long Does Melatonin Last? 

The half-life of melatonin is about 1 to 2 hours, depending on its formulation. Half-life describes the length of time it takes the body to metabolize half a dose. Since it generally takes between 4 and 5 half-lives for the human body to eliminate a drug, melatonin supplements are likely present in the body for anywhere from 4 to 10 hours, depending on the dosage and what kind you take. 

How Long Does 5mg of Melatonin Last?

Keep in mind that recommended doses tend to be between 1 and 5 milligrams, which means most melatonin supplements can stay in the body for up to 5 hours. However, the precise time frame can vary widely. Melatonin supplements affect people differently, and it could take more or less time for you to notice effects based on factors like your age and body weight, among other considerations. 

Dosage is key, and so is the type of melatonin supplement, including whether it’s a quick-release, slow-release, or a combination of the two. Melatonin can also interact with other medications and substances, including birth control pills, caffeine, some immunosuppressants, and other prescription and OTC drugs, which can affect how it works.

Keep in mind that smaller doses of melatonin will be metabolized faster than larger doses, so they won’t last in your body as long.

How To Use Melatonin

While melatonin supplements are available in both slow and fast-acting forms, some combine both formulations to better mimic how the body naturally produces melatonin through the night. Dr. Carleara Weiss, PhD, MS, RN, and sleep scientist, says the typical recommendation is to take melatonin 30 minutes to one hour before bedtime, depending on the dose and age group. That will signal the body that it’s time to wind down for sleep.

As a supplement, melatonin isn’t regulated by the Food & Drug Administration, which means dosing isn’t very well defined. In clinical studies, doses range between 0.1 and 10 milligrams. Generally, appropriate doses are low, between 1 and 5 milligrams. “Melatonin at low doses (2mg or less) is generally considered safe,” says Rohrsheib. “Higher doses of melatonin can disrupt your circadian rhythm and cause side effects such as grogginess.”

The general dosage recommendation with melatonin is to start with small doses to gauge effects, and then slowly increase if necessary. Here’s a guideline by age:

  • 3-5 years: 1-2 mg
  • 6-12 years: 2-3 mg
  • Over age 13: up to 5 mg

There is research to support melatonin as an effective option for treating short-term sleep onset insomnia in children and adults alike. However, it’s important to consult with your pediatrician before giving your child melatonin. That’s true for adults as well. “Anyone who is interested in melatonin should speak with their doctor or medical professional to determine if it’s the right thing for their situation,” says Wu.

Is Melatonin Safe?

Weiss points out that all sleep aids have side effects and contraindications, and melatonin is no exception. Studied side effects tend to be mild and include headache, nausea, dizziness, and sleepiness. Less common and more serious side effects can include:

  • Confusion
  • Mood swings
  • Stomach cramps
  • An increased risk of seizures or falls
  • Constipation
  • Diarrhea
  • Vivid dreams or nightmares
  • Short-term feelings of depression

“As a reminder, melatonin is a hormone that has side effects and interacts with other medications, so consult a sleep doctor or your primary care provider before taking it,” says Weiss. “Pregnant and lactating people should avoid taking it.”

It’s important to be choosy about your source of melatonin as well. “Melatonin supplements are not FDA regulated, so in the United States, what you get is not necessarily what’s advertised on the label in terms of dosage or even content,” says Wu. “The dosage of over the counter melatonin can be as much as five times higher than what’s on the label.” Always prioritize reputable brands.

Finally, keep in mind that melatonin supplements are intended for short-term use. “Melatonin supplements are not a long-term solution to improving your sleep and should only be reserved for temporary use unless directed by your doctor,” cautions Rohrsheib.

The Last Word From Sleepopolis 

Melatonin is an effective sleep aid for many people. However, it isn’t regulated by the FDA, so it’s important to be mindful about what you’re taking. To play it safe, it’s best to speak with your doctor for brand and dosage recommendations before taking melatonin.


Jessica Timmons

Jessica Timmons

Jessica Timmons has been working as a freelance writer since 2007, covering everything from pregnancy and parenting to cannabis, fitness, home decor, and much more. Her work has appeared in Healthline, mindbodygreen, Everyday Health, Pregnancy & Newborn, and other outlets. She loves weight lifting, a good cup of tea, and family time. You can connect with her on her website, Instagram, and LinkedIn.