Melatonin moves your body clock but is weak as a sleeping pill

Key takeaways

• In a 2013 analysis of 19 trials with 1,683 people, melatonin helped people fall asleep about 7 minutes faster and sleep about 8 minutes longer, and the American Academy of Sleep Medicine advises doctors not to use it for chronic insomnia²³.
• Its clearer job is timing: in a 2018 trial of 307 people with a late-running body clock, melatonin taken an hour before a set bedtime helped them fall asleep about 34 minutes earlier¹.
• Bigger doses aren’t automatically better: in a 2006 lab study, half a milligram moved the body clock about as far as 3 milligrams⁵.
• One study found melatonin products holding anywhere from under half to over four times their labeled dose, so choose a product with the USP Verified Mark⁷.
• A 2025 conference abstract, not yet peer reviewed, linked a year or more of recorded melatonin use with more heart failure; it can’t prove cause, but it’s one more reason not to take melatonin nightly for years without a clear reason¹⁰¹¹.

In November 2025, researchers brought a short summary to the American Heart Association’s annual meeting in New Orleans that cast an everyday supplement in an unfamiliar light¹².

Researchers led by Dr. Ekenedilichukwu Nnadi of SUNY Downstate compared the health records of 130,828 adults with insomnia¹². Over five years, 4.6% of people with long-term melatonin use on record were diagnosed with heart failure, compared with 2.7% of similar people without it¹².

The study can’t show that melatonin caused anything, and its authors said so¹⁰. But it pushed a question into the open that most users never ask: what is this hormone good for?

The answer surprises people. Melatonin is a timing signal that tells your body clock when night begins. Taken at the right hour, often in small doses, it can move a late-running clock earlier. As a nightly knockout pill, it adds only minutes.

Your body uses melatonin as a dusk signal

Your brain makes melatonin in response to darkness, and light at night can block it¹. The hormone helps set your circadian rhythm, the roughly 24-hour internal clock that helps time your sleep¹. Our articles on circadian rhythms and dark bedrooms explain that system.

That job explains melatonin’s strengths and limits. A sleeping pill pushes the brain toward sleep whenever you swallow it. Melatonin works more like a note to the clock that says “evening starts now,” so when the note arrives matters as much as how big it is.

It also clears quickly. Sweden’s official drug label for a melatonin tablet lists a half-life, the time it takes the body to clear half a dose, of about 45 minutes in healthy adults⁹. NCCIH, the National Center for Complementary and Integrative Health, notes that melatonin may stay active longer in older people and leave them drowsy the next day¹.

Many readers trust melatonin because the body makes it. That’s a fair starting point, and it’s why darkness at night and morning daylight come first. But a pill can deliver more than your body makes, and NCCIH says safety at those higher levels is less certain¹.

As a sleeping pill, melatonin adds minutes, not hours

A key summary of melatonin for ordinary sleep trouble comes from a 2013 analysis in the journal PLOS ONE. It pooled 19 randomized controlled trials, studies where chance decides who gets melatonin and who gets a look-alike placebo, with 1,683 adults and children who had primary sleep disorders².

Melatonin helped people fall asleep about 7 minutes faster and sleep about 8 minutes longer². Sleep quality improved slightly, and the benefit didn’t seem to fade with continued use². The authors noted that the effects were smaller than those of prescription sleeping pills².

In 2017, the American Academy of Sleep Medicine (AASM) issued a weak recommendation against melatonin for trouble falling asleep or staying asleep with chronic insomnia³. “Weak” means the choice can reasonably vary from patient to patient³. The same recommendation covers valerian and the antihistamine diphenhydramine³.

In 2016, the American College of Physicians also found too little evidence to recommend melatonin for chronic insomnia, and it strongly recommends cognitive behavioral therapy for insomnia, or CBT-I, as the first treatment¹. CBT-I is a short course of coaching that retrains sleep habits and worries.

Where melatonin earns its place: a clock that runs late

Melatonin does better when the problem is timing. In delayed sleep-wake phase disorder, sleep comes hours later than a person wants or needs, and mornings become a daily fight.

The AASM’s 2015 guideline on body-clock disorders gave a weak recommendation for timed melatonin in adults, children and teens with this condition⁴. NCCIH explains that “weak” reflected uncertainty over whether the benefits outweigh the harms¹. It also reports that a 2016 review of two studies, with 52 people in all, found they fell asleep about 22 minutes faster than with placebo¹.

The largest delayed-clock trial NCCIH describes came three years after that guideline. In the 2018 randomized trial, 307 people took melatonin one hour before their desired bedtime and kept a set bedtime for four weeks¹. They fell asleep about 34 minutes earlier, slept better early in the night and functioned better during the day¹.

The 2015 guideline also gave weak support to timed melatonin for blind adults whose clocks drift off a 24-hour day and for children and teens with neurologic disorders and irregular sleep⁴. It suggested that doctors avoid melatonin for irregular sleep in older people with dementia⁴.

For jet lag, NCCIH cites a 2021 review of 10 studies with 994 people that found melatonin may help after both eastbound and westbound flights¹⁵. Our travel wellness article covers jet-lag timing.

Shift work shows how experts can read the same field differently. A 2024 AASM press release said melatonin has strong evidence for adjusting sleep timing in shift work disorder⁸. NCCIH describes two 2014 reviews of shift workers as small, low in quality or inconclusive, though it also cites a 2022 review that found help¹¹⁵. We side with the more cautious reading.

Use	What the research shows	Rating
Delayed sleep-wake phase disorder, timed dose	A 307-person randomized trial (2018) and a two-study review agree on earlier sleep onset; the AASM’s weak 2015 recommendation came before the big trial, and AASM called the evidence strong in 2024148	Strong evidence for shifting sleep timing, modest size
Jet lag	2021 review of 10 studies found benefit; AASM calls the evidence strong815	Strong evidence
Shift work sleep	Reviews conflict on quality1815	Promising but early
Children with autism or ADHD	2019 review of 18 short, mostly small studies found faster sleep onset1	Promising but early; use only with a clinician
Chronic insomnia	About 7 minutes faster sleep onset; AASM advises against23	Not enough evidence for a meaningful benefit
Older adults with dementia and irregular sleep	AASM suggests avoiding it4	Evidence says no
Proof that it causes heart failure	One unreviewed observational abstract1011	Not enough evidence

A half-milligram can move the clock as far as 3 milligrams

In 2006, a research team that included sleep scientists Helen Burgess and Charmane Eastman ran a careful test of dose⁵. Forty-four healthy adults, ages 19 to 45, woke an hour earlier each morning for three days and got short bursts of bright light after waking⁵.

Each afternoon, they took 0.5 milligram of melatonin, 3 milligrams or a placebo⁵. Then the team measured how far each body clock moved.

The clock moved 2.5 hours earlier with 0.5 mg, 2.6 hours with 3 mg and 1.7 hours with placebo⁵. The two doses didn’t differ⁵. A dose six times larger bought almost nothing extra.

There’s a wrinkle. The 2013 analysis saw a borderline hint that higher doses did a bit more for falling asleep². Even so, the gains stayed small.

Americans have moved toward bigger doses anyway. A Mayo Clinic team found that melatonin use among American adults rose from 0.4% in 1999–2000 to 2.1% in 2017–2018, based on a national health survey⁶. Use of more than 5 mg a day more than tripled, from 0.08% to 0.28%⁶. The study’s funders included the National Heart, Lung, and Blood Institute and the mattress maker Sleep Number⁶.

A European drug label leans the other way. Sweden’s label for a melatonin tablet approved for children with ADHD starts at 0.5 to 2 mg and tells prescribers to find the lowest dose that works, up to 5 mg⁹.

The bottle may not match the label, and other countries treat it as a drug

In the United States, melatonin is a dietary supplement. The AASM points out that it is not under FDA oversight the way over-the-counter and prescription drugs are⁷. Our article on supplement claims explains why labels can say “supports sleep” without FDA review.

Quality varies. A 2017 study tested 31 melatonin supplements from grocery stores and pharmacies, and most didn’t match their labels¹. Some held under half the labeled amount and others over four times as much, and chewable tablets varied most⁷. About a quarter of the products contained serotonin, a related hormone that NCCIH says can be harmful even at fairly low levels¹.

Our articles on family health disagreements and third-party testing cover gummies and quality seals.

The same molecule is handled very differently abroad. NCCIH notes that several countries sell melatonin only by prescription, as a drug¹. The heart study’s authors gave the U.K. as one example¹⁰.

Sweden’s medicines agency publishes a full drug label for one melatonin tablet. It lists dosing limits, warnings and more than a dozen drug interactions⁹.

The heart-failure signal is a question, not an answer

The 2025 heart study used TriNetX, a large network of electronic health records from several countries¹⁰¹². It matched 65,414 adults with insomnia who had melatonin recorded for 12 months or more with 65,414 similar adults without that record, balancing about 40 factors such as age, blood pressure and medicines¹⁰.

Over five years, the melatonin group had more heart failure, more hospital stays for heart failure (19.0% vs. 6.6%) and more deaths (7.8% vs. 4.3%)¹².

The weaknesses are large. Over-the-counter melatonin usually isn’t recorded in health records, so many people in the “non-user” group may have taken it¹⁰. The records also mixed countries where melatonin needs a prescription with countries where it doesn’t, and they held no data on insomnia severity or psychiatric conditions¹⁰.

That matters. The lead author, Nnadi, noted that worse insomnia, depression or anxiety, or other sleep medicines could be tied to both melatonin use and heart risk¹⁰. Experts quoted by Spain’s Science Media Centre noted that a conference abstract hasn’t been reviewed the way a journal article is¹¹. One estimated the difference at about 2 extra heart failure cases per 100 users¹¹. Another noted that the finding conflicts with recent research reviews¹¹.

As of October 2026, we found no peer-reviewed paper of the full study. Marie-Pierre St-Onge of Columbia University, who has chaired an American Heart Association scientific statement and wasn’t involved, said melatonin, at least in the U.S., “is not indicated for the treatment of insomnia”¹⁰.

Our rating: not enough evidence that melatonin harms the heart. It is a fair reason to avoid taking it every night for years without a clear purpose.

Interactions and who should skip melatonin

Melatonin appears safe for short-term use in most adults, but it is a hormone, and it can interact with medicines¹⁹. Common side effects in adults include headache, dizziness, nausea and sleepiness¹.

If you…	Why it matters
Take a blood thinner such as warfarin	NCCIH advises medical supervision; Sweden’s label says to avoid the combination19
Have epilepsy	Effects on seizures are uncertain; use only with medical supervision19
Take fluvoxamine, an antidepressant	It raises melatonin levels; Sweden’s label says to avoid the pair913
Use estrogen birth control or hormone therapy	Estrogen can raise melatonin levels9
Take diabetes medicine	Melatonin may raise blood sugar; the label advises taking it apart from meals913
Take immune-suppressing drugs or have an autoimmune disease	It may weaken immune-suppressing drugs; the label doesn’t recommend it with autoimmune disease913
Take sleeping pills, sedatives or drink alcohol	Drowsiness adds up; the label advises against these combinations913
Smoke	Smoking can cut the amount of melatonin that reaches your blood roughly in half9
Are pregnant or breastfeeding	Little research exists; Sweden’s label doesn’t recommend it19
Are buying it for a child	Talk to a health professional first and store it like a medicine7

Melatonin can cause drowsiness that affects driving⁹. Don’t drive until you know how it affects you.

A melatonin decision guide

Step 1: Name your problem.

• Good fits: You fall asleep very late and can’t shift earlier; you’re crossing time zones; a clinician has diagnosed a body-clock disorder¹⁴¹⁵.
• Weak fits: You fall asleep at a normal hour but wake at 3 a.m.; you’ve had insomnia for months; you’re hoping for hours more sleep²³.
• Not without a clinician: a child, pregnancy, dementia, epilepsy or a blood thinner¹⁴⁷.

Step 2: Learn from how the studies timed it. These are research schedules, not personal prescriptions. A sleep clinician can tailor timing to your own clock.

Goal	What the research used
Fall asleep earlier with a late clock	Melatonin one hour before the desired bedtime, plus a fixed bedtime, for four weeks1
Shift the clock earlier in a lab	0.5 mg or 3 mg in the afternoon, plus earlier wake times and morning bright light5
Children with ADHD (Sweden’s label)	0.5 to 2 mg, 30 to 60 minutes before bedtime, lowest dose that works9

Step 3: Choose the product.

• Look for the USP Verified Mark. The AASM’s advisory, adopted in September 2022, notes that only four melatonin products, all 3 or 5 mg, had earned it⁷. The advisory doesn’t date that count, and it may have changed, so check the product itself.
• Pick a single-ingredient product so you know your dose.
• Prefer tablets to chewables, which varied most in testing⁷.
• Store it out of children’s reach, like any medicine⁷.

Step 4: Know when to stop.

• No clear change after about four weeks of consistent timing, the length of the 2018 trial¹.
• Next-day grogginess, headache, dizziness or nausea¹.
• Pregnancy, a new medicine from the table above, or nightly use stretching past a few months. Sweden’s label notes limited data beyond three months⁹.

When to see a clinician instead

Melatonin can’t fix every sleep problem. MedlinePlus, from the National Library of Medicine, lists signs of a possible sleep disorder¹⁴:

• You regularly take more than 30 minutes to fall asleep¹⁴.
• You often wake several times and can’t get back to sleep, or wake too early¹⁴.
• You’re often sleepy during the day or fall asleep at the wrong times¹⁴.
• A bed partner hears loud snoring, gasping, choking or pauses in your breathing¹⁴.
• You feel creeping or tingling in your legs that eases when you move¹⁴.

MedlinePlus also advises checking with your provider before taking any medicine or supplement¹⁴. A coming article in this series explains when to seek behavioral treatment or a medical evaluation. If a child swallows melatonin, call Poison Control at 1-800-222-1222.

Questions readers ask

The bottom line

Melatonin is a clock signal. Timed well, it helps people whose sleep runs late and travelers crossing time zones. As a nightly sleeping pill for chronic insomnia, it adds only minutes, and sleep experts advise against it.

If you use it, think small and well timed. Choose a verified product, check your medicines, keep it away from children, and stop if it isn’t clearly helping. A long-running sleep problem deserves a real diagnosis, not a bigger dose.

Related reading

• Travel wellness starts with the basics, not a suitcase of supplements
• Why sleep doctors oppose permanent daylight saving time
• One lit night raised heart rate and insulin resistance, while darkness costs little
• Third-party tested says what’s in the bottle, not that it works
• Most family health disagreements can wait, but a few can’t

Sources

1. National Center for Complementary and Integrative Health. “Melatonin: What You Need To Know.” NIH, last updated May 2024. nccih.nih.gov
2. Ferracioli-Oda E, Qawasmi A, Bloch MH. “Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders.” PLOS ONE, 2013;8(5):e63773 (summary in FOCUS, American Psychiatric Association). focus.psychiatryonline.org
3. American Academy of Sleep Medicine. “Pharmacologic Treatment of Chronic Insomnia in Adults: Guideline at a Glance” (Sateia MJ et al., Journal of Clinical Sleep Medicine, 2017;13(2):307–349). AASM. aasm.org
4. American Academy of Sleep Medicine. “Intrinsic Circadian Rhythm Sleep-Wake Disorders Decision Tree” (Auger RR et al., Journal of Clinical Sleep Medicine, 2015;11(10):1199–1236). AASM. aasm.org
5. Revell VL, Burgess HJ, Gazda CJ, Smith MR, Fogg LF, Eastman CI. “Advancing Human Circadian Rhythms with Afternoon Melatonin and Morning Intermittent Bright Light.” Journal of Clinical Endocrinology & Metabolism, 2006;91(1):54–59. pubmed.ncbi.nlm.nih.gov
6. National Institutes of Health. “Use of Melatonin Supplements Rising Among Adults” (on Li J, Somers VK, Xu H, Lopez-Jimenez F, Covassin N, JAMA, 2022;327(5):483–485). NIH Research Matters, March 1, 2022. nih.gov
7. American Academy of Sleep Medicine. “Health Advisory: Melatonin Use in Children and Adolescents.” AASM, adopted September 9, 2022. aasm.org
8. American Academy of Sleep Medicine. “Rethinking the Use of Melatonin as a Sleep Aid for Kids.” AASM, September 16, 2024. aasm.org
9. Swedish Medical Products Agency (Läkemedelsverket). “Mellozzan (melatonin) Tablets: Summary of Product Characteristics.” Revised November 28, 2025. docetp.mpa.se
10. Sleep Review. “Melatonin Supplements May Not Be Harmless” (on an American Heart Association Scientific Sessions 2025 abstract). November 4, 2025. sleepreviewmag.com
11. Science Media Centre Spain. Expert reactions to an AHA 2025 abstract on melatonin use for insomnia and heart failure risk. November 3, 2025. sciencemediacentre.es
12. Neurology Learning Network (HMP Global). “Melatonin for Insomnia Linked to Cardiovascular Harm.” November 21, 2025. hmpgloballearningnetwork.com
13. U.S. Pharmacist. “Although Safe for Most, Melatonin Causes Unexpected Interactions in Others.” October 30, 2019. uspharmacist.com
14. MedlinePlus. “Sleep Disorders.” National Library of Medicine, updated December 4, 2025. medlineplus.gov
15. National Center for Complementary and Integrative Health. “Sleep Disorders and Complementary Health Approaches.” NIH, last updated May 2024. nccih.nih.gov