What Really Happens to Your Body When You Take Melatonin

Whether it's a fast-approaching meeting, early flight or general anxiousness that's keeping you up, we've all struggled with the occasional sleepless night. And when all else fails to send you to dreamland, you may have been tempted to use a sleep aid, such as a melatonin pill, to help guarantee a good night's sleep.

Although melatonin is a generally safe over-the-counter dietary supplement, it can have an effect on your day-to-day sleep schedule. Plus, the label on your melatonin bottle may not be as reliable as you think. Read on to learn about what really happens to your body when you take melatonin — and whether it's worth adding to your supplement routine.

While you can certainly find melatonin in the supplement aisle of your local pharmacy, your body actually makes melatonin all by itself. Melatonin is a hormone your brain produces each night, according to the Mayo Clinic.

This hormone, produced by the pineal gland, helps regulate your body's sleep-wake cycle, also known as your circadian rhythm, according to the National Sleep Foundation. As the sun sets, the body produces more melatonin, signaling to your brain that it's time to sleep. On the flip side, your melatonin levels are lowest in the morning, helping your body wake up.

As it's synchronized with the sun, melatonin helps keep your circadian rhythm regular so you get consistent, quality rest.

In pill, capsule or gummy form, melatonin is commonly used to help address sleep difficulties, per the National Sleep Foundation — but it has different side effects than you may think.

When you add melatonin supplements to your evening routine, your brain responds just as it would with its own melatonin production. The hormone (even in pill form) signals to your brain that the sun is down and it's time to sleep.

Melatonin levels naturally increase about two hours before bedtime, according to Johns Hopkins Medicine. Contrary to common understanding, melatonin doesn't actually help you sleep but rather, puts your brain in a state of quiet wakefulness.

In other words, melatonin doesn't put you to sleep but instead helps keep your body on a regular schedule, according to Christopher Winter, MD, sleep medicine practitioner and owner of Charlottesville Neurology and Sleep Medicine Clinic.

As mentioned above, your natural melatonin tells your brain it's evening and therefore, time to go to sleep. So, when you take melatonin supplements at a different time, your circadian rhythm shifts, which is why the pills are so commonly used with jet lag, according to Dr. Winter.

Although he doesn't recommend that people use melatonin too often, it can be helpful when traveling to a new time zone or adjusting to a new nighttime work schedule, for instance. When taken at an appropriate time (an hour or two before bed), melatonin supplements may help your body acclimate and naturally fall asleep at a new time, according to the Society for Endocrinology.

But the goal here is to use supplements to help adjust to a new schedule, not to use melatonin each night, Dr. Winter says. Melatonin is like crutches for a broken leg — you use them briefly until your leg can bear weight on its own again.

The part of your brain that controls your circadian rhythm and natural melatonin production (that's your suprachiasmatic nucleus, to be precise) is also responsible for regulating your core body temperature, according to a small April 2019 study in the ​Journal of Pineal Research​.

Your body temperature typically rises as the sun sets and peaks in the evening, which is also when your melatonin levels are highest, per the above-mentioned study. After giving 10 subjects a 5-milligram melatonin supplement, researchers saw a rise in body temperature, indicating that the supplement, essentially, did its job.

But as your melatonin levels affect your body's temperature regulation and shifts in body temperature correlate to your alertness, you want to make sure to take the supplement wisely. (More on that below.)

Melatonin is generally considered safe to take. But there are a few considerations to keep in mind before you dose up.

Melatonin has been associated with some unwanted side affects, including headache, dizziness and nausea, according to the Mayo Clinic.

Perhaps even more importantly, melatonin can can cause daytime drowsiness if taken at the wrong time, so it's best to avoid driving or operating machinery within five hours of taking the supplement.

Also, if you're taking any drugs or herbs that reduce blood clotting, it's safest that you consult a medical professional before taking melatonin, as the supplement may cause a drug interaction.

Considering it's categorized as a dietary supplement, melatonin isn't closely regulated by the FDA, according to the National Center for Complementary and Integrative Health. With the lax regulation, there's no guarantee that the melatonin you're taking is accurately represented on the bottle.

There's actually a lot of variability where melatonin labels are concerned. After testing 31 different supplements, researchers found that most of the bottles didn't contain the listed amount of melatonin, ranging from 83 percent less to 478 percent more than the concentration on the label, per a February 2017 ​Journal of Clinical Sleep Medicine​ study.

Typically, bottles recommend that you take between 3 and 10 milligrams, "but the recommendations are sketchy," Dr. Winter says. Plus, there's no guarantee that the gummy or pill you're taking contains any melatonin at all (or, it could have way more melatonin than noted).

You'll want to proceed with caution where melatonin supplements are concerned. Although melatonin isn't necessarily harmful, the lack of regulation makes it a bit of a risk.

Instead, Dr. Winter recommends that you use the pills sparingly (if at all) and try your best to practice good sleep hygiene instead.