What are the side effects of melatonin?
The side effects reported most often are mild: headache, dizziness, nausea and sleepiness. Long-term safety is not known, and the clearest reported harm is young children swallowing it by accident.
By Erin Rose Updated October 12, 2026 How we score
Ask your doctor first if you take a blood thinner or any other medicine, have epilepsy, are pregnant or want to give it to a child. Who should ask
Common side effects
| Who | What was reported | Source |
|---|---|---|
| Adults, short-term studies | Headache, dizziness, nausea, sleepiness. All mild. | NIH, citing a 2015 review |
| Adults taking 10 mg or more | Drowsiness, headache and dizziness were about 1.4 times as common as on placebo (a fake pill). Serious side effects were not clearly higher, but the range of results was wide. | Menczel Schrire 2022 (4 of 79 studies were good enough to combine) |
| Children | Drowsiness, more bedwetting or urinating in the evening, headache, dizziness, agitation. Usually mild. | NIH |
| Anyone | Allergic reactions are possible. | NIH |
NIH says short-term use appears to be safe for most people. But for doses higher than what the body makes, there is not enough information yet for a clear picture of overall safety.
The high-dose review covered 79 trials and 3,861 adults taking 10 mg or more. Only 4 trials were good enough to combine in one analysis, and many trials did not report side effects at all. Its authors call the evidence limited and say longer trials need better safety reporting (Menczel Schrire 2022).
Next-day drowsiness
Melatonin can leave some people sleepy, but the studies are small. Here is what each one tested.
- Older adults. NIH says melatonin may stay active longer in older people than in younger people and cause daytime sleepiness.
- Low doses, young adults. In 12 healthy young adults, 0.3 mg and 1 mg at 9 pm caused no “hangover” on mood and performance tests the next morning (Zhdanova 1996).
- Driving. In 20 healthy adults, 5 mg taken at 4:30 pm changed 1 of 16 measures on a computer driving test an hour later. That result stayed in the normal range. People felt sleepier, and the authors advise caution when driving (Suhner 1998). This was a computer test, not real driving, and not the next morning.
- Wrong time of day. Taken early in the day, melatonin can cause sleepiness (Herxheimer 2002).
We found no large study of next-morning driving at supplement doses.
Older adults
NIH says melatonin may stay active longer in older people. It also notes that a 2015 guideline from the American Academy of Sleep Medicine advises against melatonin for people with dementia. In 24 healthy adults aged 55 to 64, one evening dose of 2 mg prolonged-release (slow-release) melatonin did not affect balance during the night (Otmani 2012). Some of that study’s authors work for Neurim, which makes that product. It was a single dose, not a study of falls.
Children and accidental swallowing
Accidental swallowing by young children is the harm with the clearest numbers. From 2012 to 2021, US poison centers logged 260,435 melatonin ingestions in children and teens, and the yearly count rose 530% (Lelak 2022, CDC). Melatonin went from 0.6% of all child ingestions reported in 2012 to 4.9% in 2021. Hospital stays rose, mostly from children 5 and under swallowing it by accident. In all, 5 children needed a breathing machine, and 2 died.
NIH adds from the same report: 94.3% of calls were for children 5 and under, and 82.8% had no symptoms. Of 4,097 people 19 and under who were hospitalized, 287 needed intensive care. The data did not show whether the two deaths were caused by melatonin. NIH also cites a 2024 CDC report of 11,000 emergency visits from 2019 to 2022 for children 5 and under who took melatonin unsupervised.
Giving melatonin to a child: NIH says to work with a doctor. The best dose and timing are not known, and there is little information on long-term effects. Because melatonin is a hormone, it might affect puberty, but no one knows for sure. Keep bottles, and gummies especially, out of reach. More on gummies.
Label accuracy
The dose you take may not be the dose on the label. Lab tests have found melatonin far off the label, and one gummy held CBD instead (Erland 2017; Cohen 2023). What the tests found, and which melatonin is on a testing list.
Medicines and conditions
NIH says anyone taking medicine should ask a doctor before using melatonin. It names two groups: people with epilepsy and people taking blood thinners need to be under a doctor’s care when taking melatonin. A 2002 Cochrane review noted case reports suggesting people with epilepsy and people taking warfarin (a blood thinner) may come to harm (Herxheimer 2002). This is not a full list. Ask your doctor or pharmacist about every medicine you take, including sleep medicines.
Long-term use
No one knows the long-term effects. NIH says information on long-term safety is lacking. We found no long-term controlled trials in adults. The only long-term data are in children with autism on a prescription-type slow-release product for up to 2 years, with no placebo group and authors tied to Neurim, the maker (Malow 2021). Growth and puberty stayed normal for age. It says nothing about everyday gummies.
The heart-failure report. A 2025 American Heart Association conference abstract looked at health records of 65,414 adults with insomnia who had a melatonin prescription and a year or more of use on record. Within 5 years, 4.6% developed heart failure. In a matched group not on melatonin, 2.7% did. This is a conference abstract, not a paper checked by outside experts (peer reviewed). It is observational, meaning it looked at records rather than testing melatonin against a fake pill, so it cannot show melatonin caused the heart failure. It did not report the dose or whether store-bought melatonin was counted.
Two 2026 papers responded. One says people who take melatonin often have worse insomnia, depression or anxiety, which can skew such studies, and found no clear link in US survey data (Khan 2026). The other calls the abstract “hypothesis-generating,” meaning it raises a question, not an answer, says it is unpublished and not peer reviewed, and calls for study of how melatonin might affect the heart (Savvidis 2026). If you have heart disease, ask your doctor.
Who should ask a doctor first
- Anyone taking medicine, especially a blood thinner (NIH).
- People with epilepsy (NIH).
- People who are pregnant or breastfeeding. NIH says there is little research on safety.
- Parents thinking of giving melatonin to a child (NIH).
- People with dementia or caring for someone who has it (NIH, citing a 2015 guideline).
- People with heart disease, given the open question above.
If none of the above applies, or your doctor says yes
For how much to take, read our melatonin dosage guide.
Questions
What are the most common side effects of melatonin?
Headache, dizziness, nausea and sleepiness, according to NIH. A 2015 review found only mild side effects in short-term studies of adults.
Does melatonin make you groggy the next day?
NIH lists sleepiness as a side effect and says melatonin may stay active longer in older people, causing daytime sleepiness. A small study of 0.3 and 1 mg in young adults found no next-morning effect on tests (Zhdanova 1996). We found no large study of next-morning driving.
Is it safe to take melatonin every night?
NIH says short-term use appears to be safe for most people, but there is little information on long-term use. We found no long-term controlled trials in adults.
Is melatonin habit-forming?
We found no study that answers this. Two short trials of a 2 mg slow-release melatonin drug in people 55 and older found no withdrawal effects or rebound sleep problems when people stopped after about 3 weeks (Lemoine 2007; Luthringer 2009). Both had authors who work for Neurim, which makes that drug.
Does melatonin cause heart failure?
No one knows yet. A 2025 conference abstract found more heart failure among insomnia patients with a year or more of melatonin prescriptions. It is not a peer-reviewed paper, and it is observational, so it cannot show melatonin was the cause. One 2026 paper found no clear link in US survey data; another called the abstract a question to study further and noted it is unpublished. If you have heart disease, ask your doctor.
What drugs should not be taken with melatonin?
NIH names two groups: people taking blood thinners and people with epilepsy need a doctor’s care when taking melatonin. This is not a full list. Ask your doctor or pharmacist about every medicine you take, including sleep medicines.
What should I do if my child swallowed melatonin?
Call Poison Control at 1-800-222-1222. Most children seen by poison centers for melatonin had no symptoms, but some were hospitalized (CDC, as reported by NIH).
How much melatonin to take · the best melatonin · melatonin guide.
Sources
- NIH National Center for Complementary and Integrative Health. Melatonin: What You Need To Know (last updated May 2024; read October 12, 2026).
- Menczel Schrire Z, et al. Safety of higher doses of melatonin in adults: a systematic review and meta-analysis. J Pineal Res. 2022. PubMed 34923676
- Lelak K, et al. Pediatric melatonin ingestions, United States, 2012–2021. MMWR. 2022. PubMed 35653284
- Zhdanova IV, et al. Sleep. 1996. PubMed 8843534
- Suhner A, et al. J Travel Med. 1998. PubMed 9772309
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002. PubMed 12076414
- Otmani S, et al. Hum Psychopharmacol. 2012. PubMed 22350925 (authors include Neurim staff)
- Lemoine P, et al. J Sleep Res. 2007. PubMed 18036082 (authors include Neurim staff)
- Luthringer R, et al. Int Clin Psychopharmacol. 2009. PubMed 19584739 (authors include Neurim staff)
- Malow BA, et al. J Am Acad Child Adolesc Psychiatry. 2021. PubMed 31982581 (authors include Neurim staff)
- Erland LA, Saxena PK. J Clin Sleep Med. 2017. PubMed 27855744
- Cohen PA, et al. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA. 2023. PubMed 37097362
- Nnadi et al. Abstract 4371606: Effect of long-term melatonin supplementation on incidence of heart failure in patients with insomnia. Circulation. 2025;152(suppl 3). doi:10.1161/circ.152.suppl_3.4371606 (conference abstract, not peer reviewed as a paper)
- Khan B, Lima BB. Open Heart. 2026. PubMed 42167796
- Savvidis C, et al. World J Exp Med. 2026. PubMed 42394777