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Melatonin Side Effects Guide

Mary Lucas, RN

Reviewed by Mary Lucas, RN

Written by Nicholas Gibson

Published 04/24/2022

Updated 04/25/2022

If you’ve ever looked into supplements for insomnia, delayed sleep-wake phase disorder and other issues related to sleep, you’ve probably heard of melatonin.

Melatonin is a hormone produced by your body to regulate certain aspects of your night and day cycle. Melatonin supplements are used to treat sleep difficulties and make getting a full night’s sleep easier.

Most research suggests that melatonin is safe and effective. However, like other supplements, it’s possible for melatonin to cause side effects.

Below, we’ve explained what melatonin is, as well as how it works as a supplement for primary sleep disorders. We’ve also listed the potential side effects and drug interactions you should be aware of before using melatonin, as well as some tips for using melatonin safely.

Melatonin is a hormone that’s secreted by your pineal gland, a small gland in your brain. Your body produces melatonin in response to darkness — a fact that’s earned melatonin that rather ominous-sounding nickname of “hormone of darkness.”

As a hormone, melatonin helps regulate your body’s circadian rhythms — a series of internal processes that are responsible for helping you operate on a 24-hour schedule. It plays a major role in helping you feel tired at night and signaling that it’s time to fall asleep.

While darkness stimulates your body to produce melatonin, exposure to light has a suppressive effect on the release of melatonin. This process — of releasing melatonin at night and reducing melatonin levels during the daytime — helps you to maintain healthy, consistent sleep habits.

Beyond its effects on sleep, melatonin is believed to play other roles in your physical health and wellbeing. However, research on the non-sleep effects of melatonin is limited.

Some people have unusually low levels of melatonin — an issue that may cause sleep problems such as insomnia and circadian rhythm disorder. Taking a melatonin supplement shortly before bedtime may help these people to fall asleep and stay asleep throughout the night.

Melatonin supplements are also used to treat short-term sleep issues, such as jet lag and sleep disorders caused by working a night shift.

Unlike many other sleep aids, melatonin is a dietary supplement, not a medication that requires a prescription from your healthcare provider.

According to the National Center for Complementary and Integrative Health, use of melatonin in the short term is generally considered safe. However, like other dietary supplements, melatonin can potentially cause some side effects.

Potential side effects of melatonin include:

  • Nausea

  • Headache

  • Dizziness

  • Sleepiness

  • Increased immune function

  • Elevated blood pressure

  • Increased risk of seizures

Melatonin can also affect your alertness and ability to focus on specific tasks. It’s best to avoid driving, operating machinery or doing anything else that puts you at risk of injury for four to five hours after taking melatonin.

In women, melatonin, especially in large doses, has been linked to amenorrhea — a condition in which menstrual periods stop. This issue may be related to suppression of gonadotropin-releasing hormone (GnRH), a hormone that’s involved in regulating the menstrual cycle.

Research suggests that any changes in the menstrual cycle caused by melatonin reverse with the cessation of melatonin supplements.

Currently, there’s limited scientific research about the safety of melatonin during pregnancy or breastfeeding. Women who are pregnant or breastfeeding should avoid using melatonin as a sleep aid.

Unlike benzodiazepines, Z-drugs and prescription medications for sleep, melatonin isn’t linked to any withdrawal symptoms or dependence.

If you feel sick or experience any other side effects after using melatonin, make sure to talk to your healthcare provider.

Some medications may interact with melatonin and either increase or decrease its effectiveness or change the way it’s broken down by your body. Some medications may affect your production of natural melatonin.

Medications, supplements and other substances that may interact with melatonin include:

  • Antidepressants, such as fluvoxamine (Luvox®)

  • Diabetes medications

  • High blood pressure medications

  • Medications for autoimmune diseases

  • Medications affected by cytochrome CYP1A2 and CYP2C19 substrates

  • Seizure threshold lowering drugs

  • Anticoagulants and antiplatelet drugs

  • Anticonvulsants used to prevent seizures

  • Sedative medications

  • Birth control pills

  • Warfarin

  • Methamphetamine

  • Caffeine

To reduce your risk of experiencing drug interactions, it’s best to talk to your healthcare provider before using melatonin. Let them know about any medications and dietary supplements you use on a regular basis, as well as any medications you’ve used recently.

It’s especially important to talk to your healthcare provider if you have epilepsy or use any type of blood thinner, as this may increase your risk of experiencing issues with melatonin.

Melatonin is generally a safe and effective supplement when it’s used as recommended. Follow the steps below to get the best results from melatonin while reducing your risk of side effects or interactions:

  • Use melatonin 30 minutes to two hours before bedtime. Taking melatonin earlier or later than this may make it less effective. If you need help timing your dose of melatonin, try setting an alert on your phone approximately one hour before bedtime.

  • Take the recommended dose of melatonin. If you use a melatonin supplement, check the label for the recommended dose for adults before taking it. If the packaging suggests a range of dosages, start with the lowest dose to see how you respond.

  • Talk to your healthcare provider before using melatonin. Even though melatonin is a supplement rather than a drug, it’s best to talk to your healthcare provider before adding it to your routine.
    Make sure to inform your healthcare provider about your medical history, as well as any medications you currently use or have recently used.

  • Use melatonin as a short-term supplement, not every night. Most research suggests that short-term use of melatonin is safe. Try to use melatonin only when you need it for falling asleep, not as an every-night sleep supplement.

  • Don’t combine melatonin with other sleep aids. Avoid taking other over-the-counter dietary supplements or prescription sleep medications while you’re using melatonin, as using these together may increase your risk of side effects or drug interactions.

  • Try not to take melatonin with alcohol. Melatonin should not be used with alcohol. If you’ve consumed alcohol, try to sleep naturally and avoid using melatonin or any other sleep aids.

  • Avoid driving or operating machinery after using melatonin. Melatonin may affect your alertness and make driving unsafe. Avoid driving any type of vehicle or operating machinery for four to five hours after taking a melatonin supplement.

Supplemental melatonin works best when it’s combined with good sleep habits and a balanced, healthy lifestyle. Use the following habits and techniques to get deeper sleep and better results from melatonin:

  • Avoid caffeine and other stimulants in the afternoon. Caffeine can make it difficult to fall asleep. It may also affect melatonin levels in your body. Avoid taking in caffeine and other stimulants in the afternoon, evening or hours before bed.

  • Keep yourself physically active. Exercising during the day may help you fall asleep faster at night. Try to get at least 150 minutes of aerobic exercise per week, even if it’s just a brisk walk or bike ride around your neighborhood.

  • Maintain a consistent bedtime. Good bedtime habits usually result in more consistent, refreshing sleep. Even if you’re a night owl, try to maintain a regular bedtime and wake up at the same time every day, including on weekends.

  • Avoid screens and electronic devices before bed. Exposure to bright light can slow down your body’s natural melatonin production. Try to switch off your computer, phone and other electronic devices before bed and keep them out of your bedroom.

  • Keep your bedroom quiet, cool and comfortable. A comfortable environment makes falling asleep and staying asleep easier. Keep your bedroom as dark as possible when it’s time to sleep, and set a temperature that helps you feel comfortable in bed.

  • Use techniques to deal with sleep anxiety. Melatonin can help you to feel tired, but it isn’t a treatment for nighttime anxiety. Our guide to sleep anxiety shares techniques that you can use to calm your mind and make falling asleep easier. 

Melatonin is a safe and effective supplement for most people that can make falling and staying asleep easier. However, like all supplements, it does have the potential to cause some adverse effects and interactions.

To use melatonin safely, follow the instructions that come with your supplement and talk to your healthcare provider if you currently use any over-the-counter or prescription medications. 

Interested in trying melatonin? Our Sleep Supplement, which is part of our range of men’s specialty supplements and vitamins, contains 4mg of time-release melatonin to keep you asleep throughout the night and help you wake up feeling refreshed and ready. 

Need more help falling asleep? Our guide to insomnia explains why you might find it difficult to fall asleep at night, as well as the most effective options for relaxing, beating nighttime anxiety and successfully getting a refreshing night’s sleep. 

6 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. Melatonin. (2021, December 13). Retrieved from
  2. Masters, A., Pandi-Perumal, S.R., Seixas, A., Girardin, J.-L. & McFarlane, S.I. (2014). Melatonin, the Hormone of Darkness: From Sleep Promotion to Ebola Treatment. Brain Disorders & Therapy. 4 (1), 1000151. Retrieved from
  3. Melatonin: What You Need to Know. (2021, January). Retrieved from
  4. Savage, R.A., Zafar, N., Yohannan, S. & Miller, J.M. (2021, August 15). Melatonin. StatPearls. Retrieved from
  5. Tips for Better Sleep. (2016, July 15). Retrieved from
  6. How much physical activity do adults need? (2022, March 17). Retrieved from
Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Mary Lucas, RN

Mary is an accomplished emergency and trauma RN with more than 10 years of healthcare experience. 

As a data scientist with a Masters degree in Health Informatics and Data Analytics from Boston University, Mary uses healthcare data to inform individual and public health efforts.

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