What Taking Melatonin Every Night Really Does To Your Body

When it comes to supplements that claim to help you sleep better, one reigns supreme: melatonin. According to WebMD, more than 3 million adults and nearly 500,000 children took it in 2018. By 2020 Americans were spending more than $825 million on melatonin supplements annually (via Business Insider).

Melatonin is actually a hormone produced by the brain's pineal gland in response to darkness. It helps ground your circadian rhythm and tells the body that it's time to wind down for sleep. Supplemental melatonin is usually made synthetically, though it can also be derived from animals or microorganisms (via the National Center for Complementary and Integrative Health). According to the National Sleep Foundation, there are no official dosage guidelines for melatonin, though most adults take between 0.5 and 5 milligrams. It's best to take melatonin about an hour before bed and to start with a low dosage and only increase if you're not seeing results. Additionally, melatonin is only meant to be taken short term.

But just how effective is melatonin for various sleep issues? Can it help with anything else besides a good night's rest? Is it really as harmless as people think it is?

Melatonin may improve your insomnia, but not as much as you'd think

According to a 2016 study published in the Journal of Family Medicine and Primary Care, approximately one-third of American adults may suffer from chronic insomnia (at least three nights a week for three months or longer). Insomnia — defined as difficulty falling or staying asleep — can have many causes. These include stress, depression, anxiety, use of certain medications or substances, and disruptive elements in your sleeping environment like light and noise. People with insomnia often don't get enough high-quality sleep, leading to daytime sleepiness, mood changes, and difficulty concentrating (via WebMD).

Since melatonin is the hormone that cues the body that it's time to sleep, it makes sense that taking supplemental melatonin would swiftly whisk insomniacs off to dreamland. According to WebMD, however, the supplement's effect on both sleep latency (how quickly someone falls asleep) and total sleep time are minimal. Popping a melatonin pill before bed appears to shave only an average of seven to 12 minutes off the time insomniacs spend tossing and turning. And, while some people may report feeling better rested after taking melatonin, the objective data doesn't always back up their subjective conclusions.  

If you have difficulty falling asleep at bedtime, melatonin can help

We all occasionally have trouble falling asleep when we know we "should," but for some people it's a chronic issue that's a recognized sleep disorder (via National Sleep Foundation). Individuals with delayed sleep-wake phase syndrome, also known as delayed sleep-wake phase disorder (DSPD), have difficulty falling asleep and waking up at socially acceptable times. Those with DSPD are essentially extreme "night owls" who don't feel sleepy until, say, 4 a.m. and, if they had their way, might sleep until noon.

DSPD occurs because the body doesn't release melatonin at the proper time. Trying to conform to the hours other people keep can be extremely difficult and often results in individuals with DSPD not getting enough sleep, leading to excessive daytime sleepiness and difficulty concentrating. Taking supplemental melatonin can be extremely helpful because it allows those with DSPD to trigger sleepiness earlier than they'd naturally start winding down, according to the National Sleep Foundation.

A 2020 meta-analysis published in the journal Sleep found that supplemental melatonin "decreased sleep-onset latency by 23.27 minutes" in children and adults. It also decreased the amount of time it took them to fall asleep once their head hit the pillow. Interestingly, taking supplemental melatonin caused the release of their own natural melatonin to occur 1.18 hours earlier in the night.

Melatonin can prevent or treat jet lag

Humans didn't evolve with the ability to travel across the globe in a matter of hours, so our bodies aren't well-equipped to deal with sudden time zone changes. According to the Mayo Clinic, "Jet lag occurs because your body's clock is still synced to your original time zone, instead of to the time zone where you've traveled." Jet-lagged travelers can experience difficulty falling asleep at the right time and may experience daytime sleepiness, mood changes, and GI upset.

The more time zones you cross, the worse your jet lag is likely to be, especially if you're traveling from west to east. Changes in airline cabin pressure and humidity levels may also contribute to jet lag. It takes about a day per time zone crossed to recover. Taking melatonin can help sync your body to your new locale, but timing matters. If you've traveled east and "lost" time, you should take melatonin at bedtime. If you've traveled west and "gained" time, melatonin should be taken in the morning.

A 2002 meta-analysis published in The Cochrane Database of Systematic Reviews found that doses of between 0.5 and 5 milligrams of melatonin helped prevent or treat jet lag when more than five time zones were crossed. Interestingly, extended-release melatonin didn't have the same beneficial effects because it caused melatonin levels to rise too slowly.

If your circadian rhythm is constantly shifting, melatonin can help

Your circadian rhythm is tied to the phases of light and dark that make up a day. However, some people's internal clocks are out of sync with this 24-hour cycle. Individuals with non-24-hour sleep-wake disorder (N24SWD) have a circadian rhythm that is either shorter or longer than 24 hours (via National Sleep Foundation). This discrepancy between the length of their circadian rhythm and the 24-hour day progressively shifts their sleep and wake times.

As an extreme example, if someone's rhythm is only 20 hours, they may feel sleepy at 10 p.m. one day but 6 p.m. the next day and 2 p.m. the day after. This constant shifting can lead to significant fluctuations in alertness, mood, and appetite and can make it very difficult to keep work and social commitments. Oftentimes, people with N24SWD have complete vision loss; the condition is caused by the inability to perceive light. N24SWD can also affect sighted individuals, although the cause is unclear (via National Sleep Foundation).

In a small study of sighted patients with N24SWD published in the Journal of Clinical Sleep Medicine in 2018, researchers found that melatonin, when timed correctly and combined with light therapy, could effectively "train" participants' circadian rhythm to follow a 24-hour pattern. Most, however, chose not to continue the treatment after the study ended.

Melatonin has the potential to be useful in the treatment of certain cancers

While no one's suggesting that cancer patients forgo chemotherapy or radiation treatment in favor of an over-the-counter dietary supplement, melatonin may be beneficial as an additional treatment in some circumstances.

According to a 2017 paper published in Oncotarget, melatonin may prevent the development or spread of cancer in a number of ways. Melatonin is an antioxidant, which means it helps prevent free-radical damage in the body that, over time, could lead to the growth of cancerous cells. It may also stimulate apoptosis — a process by which diseased or damaged cells "self-destruct" before they can cause harm. Melatonin may also interfere with a tumor's ability to create its own blood supply (angiogenesis), which is a prerequisite for it spreading to other parts of the body.

Additionally, clinical trials have found that melatonin given alongside chemotherapy might make this treatment more effective and reduce the severity of side effects patients experience. Although evidence suggests melatonin may be useful for a wide variety of cancers, it appears to be particularly beneficial for hormone-dependent cancers such as breast, cervical, and ovarian cancers. While this research is promising, it's important to note that these findings come from either animal or in vitro (cells in a petri dish) studies. The paper's authors caution that more research is needed.

It's unclear if melatonin can prevent migraines

Do you get frequent migraines? Melatonin might just help ward them off. A 2010 study published in Headache: The Journal of Head and Face Pain found that individuals who suffered chronic migraines had significantly lower levels of naturally produced melatonin than did those who never or only occasionally got migraines. It makes sense, then, that supplementing with melatonin might be helpful, but the research so far hasn't been conclusive.

On the one hand, a 2016 study published in Neurology, Neurosurgery & Psychiatry showed promising results. Researchers gave participants — all of whom had a history of two to eight migraines per month — either 3 milligrams of melatonin, 25 milligrams of amitriptyline (a commonly prescribed migraine medication), or placebo daily for three months. Those who took the melatonin had 2.7 fewer migraine days per month, whereas those on the amitriptyline had 2.2 fewer and those on placebo had 1.1 fewer. So although melatonin clearly provided a benefit compared to the placebo, it was essentially on par with the amitriptyline. But the researchers noted that the melatonin takers had fewer side effects than those taking the amitriptyline. This suggests melatonin may be safer and just as effective as prescription migraine medications.

However, a 2010 study published in Neurology found that 2 milligrams of extended-release melatonin given an hour before bed for eight weeks had no significant effect on the number of migraines participants experienced.

If you have endometriosis, melatonin might help

Endometriosis is a painful condition in which endometrial tissue that normally lines the inside of the uterus grows elsewhere in the body — usually the ovaries, fallopian tubes, or the pelvic wall. This tissue behaves as it would if it were in the uterus: it thickens and then sheds over the course of the menstrual cycle. But since it's not in the uterus, this tissue has no way to exit the body after it breaks down each month. This can lead to symptoms such as heavy or extremely painful periods, pain during sex or bowel movements, and infertility. Treatment can include pain medications, hormone therapy, and, in severe cases, surgical removal of the uterus, fallopian tubes, and ovaries (via Mayo Clinic).

According to a 2013 study published in the journal Pain, melatonin can offer relief for those with painful endometriosis symptoms. The researchers gave participants 10 milligrams of melatonin daily for eight weeks and found that it reduced daily pain scores by 39.8% and dysmenorrhea (painful periods) by 38%. As a bonus, it improved individuals' sleep (no surprise there) and reduced their likelihood of using pain medication by 80%.

Melatonin probably won't help with depression

While melatonin may be useful for a number of conditions, there isn't much evidence to support the idea that it's helpful for those with depression. In fact, a 2006 paper published in The World Journal of Biological Psychiatry noted that people with depression tend to have significantly higher levels of endogenous melatonin (that is, their bodies produce more melatonin). This might explain why some depressed individuals sleep more than usual. So taking exogenous (supplemental) melatonin likely wouldn't help and might even make things worse. When it comes to seasonal affective disorder (SAD), the researchers noted that there were "changes in the onset, duration and offset of melatonin secretion."

A 2017 meta-analysis published in Acta Psychiatrica Scandinavica reviewed eight previously published studies to see how taking melatonin might impact both major depressive disorder and SAD. The researchers concluded that "the evidence for an effect of melatonin in improving mood symptoms is not significant." However, an earlier study conducted by researchers at Oregon Health & Science University concluded that melatonin could be useful for people with SAD. The catch was that it had to be a small dose and couldn't be taken at bedtime. "Night owl" SAD patients who had trouble falling asleep benefited from taking low-dose melatonin in the afternoon or evening, while "morning lark" SAD patients who woke up way too early benefited from taking melatonin in the morning.

Melatonin can be helpful for TMD

Temporomandibular joint (TMJ) disorders (TMD) are a group of painful condition affecting the hinge joint of the jaw and the facial muscles surrounding it. While anyone can get TMJ pain, risk factors include arthritis in the jaw, jaw injuries, regularly grinding or clenching your teeth, and certain connective tissue disorders. Although pain is usually temporary and manageable with medications such as pain relievers, anti-inflammatory drugs, and muscle relaxants, sometimes surgery is necessary (via Mayo Clinic).

In a 2013 study published in the Oman Medical Journal, researchers had participants engage in a six-day simulated mission to Mars to see how sleep quality and stress levels affected their TMD. It's probably no surprise that the poor sleep and stressful situations they experienced during the simulation caused their TMD symptoms to worsen. (Is there anything that actually improves with crappy sleep and loads of stress?)

The connection between poor sleep and TMD symptoms is a two-way street. Not only does poor sleep appear to trigger flare-ups of TMJ pain, but according to a 2013 study published in the Journal of Pain and Symptom Management, individuals with TMJ tend to have less restorative sleep. However, the researchers found that melatonin improved the participants' sleep quality and had an analgesic (pain-killing) effect. Melatonin reduced the individuals' pain scores by about 44%.

The jury's still out on melatonin's effects on blood pressure

High blood pressure (hypertension) is a major health problem in the United States. According to the Centers for Disease Control and Prevention, approximately 45% of Americans have hypertension, defined as a systolic blood pressure (the pressure in the arteries when the heart contracts) of 130 mmHg or greater or a diastolic blood pressure (the pressure in the arteries when the heart relaxes between beats) of 80 mmHg or greater. Having high blood pressure greatly increases your risk for both heart disease and stroke.

If you have hypertension, you may be looking into ways to lower it. And, in fact, you might have heard that melatonin is a "natural" way to lower high blood pressure, but experts haven't reached a consensus on this yet. On the one hand, a 2004 study published in Hypertension found that taking 2.5 milligrams of melatonin daily for three weeks decreased individuals' systolic blood pressure by 6 mmHg and decreased diastolic blood pressure by 4 mmHg. A single dose of melatonin, however, had no effect. On the other hand, the Mayo Clinic cautions that melatonin may worsen blood pressure among those already taking medications to manage their high blood pressure.

Melatonin could help prevent sunburns

While the vast majority of people take melatonin in pill form at night to help them sleep, topical melatonin may actually protect your skin from harmful UV radiation. A 2013 paper published in Photodermatology, Photoimmunology & Photomedicine examined 16 previously published studies and concluded that melatonin can protect the skin from sun damage if applied beforehand, though it had no effect on repairing sun damage after the fact.

Melatonin protects skin directly by serving as an antioxidant, battling the free-radical damage UV light causes, and indirectly by controlling the expression of genes that can stabilize damaged DNA. But don't throw away your bottle of sunscreen just yet. The authors cautioned that all 16 studies used artificial UV light (think: tanning beds) rather than natural sunlight, so it's unclear how well melatonin would perform during your day at the beach. It's also unclear what concentration of melatonin would provide optimal protection.

Sunburns may not seem like a big deal — after all, more than one in three Americans get one each year — but they're a major risk factor for skin cancer. More than 5 million cases of skin cancer are diagnosed in the United States annually, making it the most common form of cancer. Of those, about 63,000 cases are melanoma, the deadliest form of skin cancer; nearly 9,000 Americans die each year of melanoma (via Office of the Surgeon General).

You may experience some mild side effects

When it comes to dietary supplements, melatonin is considered one of the safest. As a 2016 paper published in Clinical Drug Investigation concluded, "In general, animal and human studies documented that short-term use of melatonin is safe, even in extreme doses." The authors noted that even long-term usage of melatonin causes only "mild adverse effects comparable to placebo." The Mayo Clinic agrees, highlighting the fact that, unlike some other sleep medications, melatonin doesn't appear to be habit-forming. In addition, individuals don't seem to become habituated to melatonin, meaning they don't need to take larger and larger doses as time goes on in order to get the same results.

But that doesn't mean melatonin is totally without side effects. As the Mayo Clinic explained, some people may experience headache, dizziness, nausea, or daytime drowsiness. More rarely, taking melatonin could cause feelings of depression, anxiety, or irritability; disorientation; tremors; or abdominal cramps. The National Center for Complementary and Integrative Health (NCCIH) cautioned that, as with any substance, it's possible to have an allergic reaction to melatonin. The NCCIH also noted that melatonin may be riskier (due to its long-term effects being less well-known) for certain groups, including breastfeeding or pregnant women, children, and older adults.

Melatonin may interact with other medications

The melatonin supplement you take at night may be chemically identical to the hormone your body produces naturally, but it can still interact negatively with certain prescription medications you may also be taking. According to WebMD, melatonin should not be taken with sedatives (medications that depress the central nervous system and cause sleepiness). This combo can cause excessive sleepiness that could make tasks like driving unsafe. Common sedatives include the sleep aid zolpidem (Ambien), the anti-seizure drug clonazepam (Klonopin), and the anti-anxiety drug lorazepam (Ativan).

You should also exercise caution if you're taking melatonin in addition to birth control pills. Oral contraceptives appear to increase the amount of melatonin your body naturally produces, so when combined with melatonin supplements you could end up with too much melatonin circulating in your system. Additionally, if you're taking the antidepressant fluvoxamine (Luvox), your body may absorb more of the melatonin you take, making side effects more likely or more intense. Melatonin may also slow blood clotting, so if you're already on blood thinners, you could be at increased risk for bruising and bleeding. And, because melatonin can increase blood sugar levels, it may make diabetes medications less effective. Before taking melatonin or any other supplement, consult your doctor or pharmacist about potential drug interactions.

Choose your melatonin supplements carefully

Just because the label lists how much melatonin each pill contains doesn't mean that's actually what's in the bottle. A 2017 study published in the Journal of Clinical Sleep Medicine examined the actual contents of 31 melatonin supplements and noted that "melatonin content was found to range from −83% to +478% of the labelled content."

Melatonin, along with all dietary supplements, falls into a regulatory gray area. The Food and Drug Administration (FDA) doesn't have the authority to review the safety or effectiveness of dietary supplements before they're put on the market. It's up to manufacturers to ensure that their products are safe and contain the quantity and quality of ingredients they claim to have.

If you want to ensure the melatonin you're taking is on the up-and-up, look for bottles with the USP Verified label. The United States Pharmacopeia (USP) program is an independent certification program that evaluates the quality of dietary supplements. If you see the label on a bottle, you can be assured that the product contains the listed ingredients in the amounts and potency claimed. The USP Verified label also indicates that a product doesn't contain harmful levels of certain contaminants, such as mercury, lead, and pesticides. It also certifies that the supplement breaks down in the body in the way and at the speed it's supposed to. Finally, the USP label denotes that the product was made according to the FDA's Good Manufacturing Practices.