July 26, 2023

What Happens to Your Body if You Take Melatonin Every Night, According to a Behavioral Sleep Medicine Expert

Dr. Deirdre Conroy was quoted in this article. 

Read the full Parade article here. 


According to Dr. Deirdre Conroy, Ph.D., a clinical professor in the Department of Psychiatry at the University of Michigan and the clinical director of the university’s Behavioral Sleep Medicine Program, someone should consider taking melatonin if they’re having trouble falling asleep.

Generally, she says that melatonin is most helpful for initially falling asleep. So if you lie in bed for hours unable to fall asleep, taking a melatonin supplement could potentially help. Dr. Conroy adds that people who have trouble staying asleep (AKA people who wake up throughout the night) may want to consider an extended-release melatonin, which may be helpful for both initially falling asleep and staying asleep.

It’s important to know that supplements are not regulated by the Food and Drug Administration. To ensure you’re buying a supplement that’s actually worth the money, Dr. Conroy recommends researching the brand through a website such as Consumer Lab, which independently tests supplements for dose and purity. “One of the challenges with melatonin is that recent studies have shown that the dose on the bottle may not always equate to exactly how much is in each pill,” Dr. Conroy says. Third-party testing companies, such as Consumer Lab, test supplements to ensure the dose on the label matches up with what’s in the products.

What Happens to Your Body if You Take Melatonin Every Night

When it comes to taking melatonin, don’t assume that the higher the dose, the better it will work. In fact, Dr. Conroy says that a low dose of melatonin (between .3 and .5 milligrams) is more effective than a bigger dose. "A lower dose of melatonin has been shown to show a bigger 'shift' in the circadian phase than larger doses of melatonin," she says. "Scientific studies published in the Journal of Biological Rhythms and The Journal of Clinical Endocrinology & Metabolism show that a maximum shift occurred 0.5 milligrams compared to a previous study with 3 milligrams." Dr. Conroy adds that the best time to take melatonin is four to six hours before heading to bed.

Can you expect to have an amazing night of sleep the first day you start taking melatonin? Dr. Conroy says that this depends on the person and the reason why they’re taking it. “For example, melatonin might ‘work’ for someone who is taking it for a brief bout of insomnia. However, if melatonin is being used to ‘shift’ the body clock in a night owl, it might take some time to notice a difference,” she says, adding that how quickly someone will notice the effects of melatonin also depends on other behavior changes they may be making, such as if they’ve started getting up earlier every day, which can help lead to feeling more tired at night.

Though melatonin is not used for mood management (such as a way to manage anxiety or depression), Dr. Conroy says that taking melatonin every day could indirectly impact the way you feel. For example, if it allows you to get consistently better sleep, you may find yourself feeling less cranky and generally happier than when you weren’t getting good sleep.

Dr. Conroy says that taking melatonin every night also impacts body temperature. “There is an intricate connection between body temperature and melatonin,” she says. She explains that our core body temperature naturally declines at night, which causes melatonin levels to rise. “[Supplement] forms of melatonin may contribute to small rises in skin temperature,” she says. However, she adds that these are very small changes and likely go undetected.

Before taking melatonin, it's also important to be aware of the potential side effects. These can include headaches, dizziness, feeling sleepy during the day, stomach aches, dry mouth, dry or itchy skin, arm or leg pain, strange dreams, and night sweatsSome people also experience changes in appetite, urinary incontinence, short-term depression, increased risk of falling and increased risk of seizures. For these reasons and because melatonin may interact with other medications, Dr. Conroy says that anybody interested in taking melatonin should talk to their doctor first. People who are pregnant, breastfeeding, have a seizure disorder, an autoimmune disorder, or are depressed should not take melatonin.  

Since the dose of melatonin in supplements is often inconsistent, it’s hard to study other ways taking melatonin consistently affects the body. However, some research shows that it may benefit cardiovascular health (at least in rats). One scientific study published in the World Journal of Gastroenterology also found that taking melatonin could be beneficial for people with irritable bowel syndrome.

While more studies need to be done in order to know exactly how taking melatonin every day affects the body, what science is clear about is that not getting consistently good sleep negatively affects the body in major ways. This includes cognitive decline, mental health challenges, and increasing risk of cardiovascular disease. For this reason, Dr. Conroy suggests that anyone who is regularly experiencing sleep problems see a behavioral sleep medicine doctor. (The Society of Behavioral Sleep Medicine has a directory so you can find one near you.) Depending on why you are having sleep problems, taking a melatonin supplement may be part of your sleep solution or your specialist may choose to focus more on lifestyle habits. While melatonin is safe to use long-term, she says it's still important to address the root causes of why you aren't sleeping well so you do not have to rely on a supplement.