Research · Oct 11, 2026

Melatonin and heart failure: six claims checked

Qaytona Team · 6 min read

An extreme close-up of a blue eye flecked with amber, in warm light.

The melatonin and heart failure headlines come from a November 2025 conference abstract that still hasn't been published as a full paper. Among adults with insomnia, those with a year or more of melatonin in their health records were diagnosed with heart failure more often over five years than those with none: 4.6% against 2.7%. The study couldn't see melatonin bought over the counter, and no trial has tested long-term use against heart failure. Here is how six claims from the coverage, and from the replies to it, hold up.

"Long-term melatonin use linked to 90% higher heart failure risk"

The number is right, and it isn't new. The abstract reports a hazard ratio of 1.89. In absolute terms that is about 2 more diagnoses per 100 users over five years. ¹

That headline ran on ScienceDaily on August 29, 2026, with no journal reference. It repeats the American Heart Association's November 2025 press release, which describes the work as preliminary research presented at its meeting. ²

It's about the melatonin people buy at the store

The study couldn't see it. Users were adults with at least one melatonin prescription and a year of use in their records, and controls had none recorded. The database mixes countries where melatonin needs a prescription, such as the UK, with the US, where it doesn't. By the AHA's own account, anyone in the US taking it over the counter would have been counted as a non-user. ³

Where melatonin needs a prescription, a year of it is likely to mark someone whose sleep problem was hard to treat. The study had no measure of insomnia severity, depression or anxiety. In US survey data, melatonin users were nearly three times as likely as non-users to report a sleep problem and more than twice as likely to report depression. ⁴

Users were twice as likely to die

It's in the data, and it's a warning sign about the comparison. Deaths from any cause were 7.8% against 4.3%. The count includes every cause of death, cardiac or not, and a near-doubling across all of them suggests the users were sicker in ways the matching didn't capture. The lead author says the study can't prove cause and effect. ³

Users were hospitalized for heart failure three times as often

Hard to interpret. More users were admitted to hospital with heart failure, 12,411, than were ever diagnosed with it, 3,021, in a group that excluded heart failure at the start. The authors put that down to how admissions are coded. ¹

The trials show melatonin is safe for the heart

For short use in heart patients, mostly yes. Long-term use hasn't been tested. Across 14 randomized trials in 1,027 people with heart disease, none reported a serious side effect from melatonin, and ejection fraction rose about 4 points on low-certainty evidence. None lasted more than 24 weeks or counted heart failure events. ⁵

A survey analysis published in May 2026 found no link between recent melatonin use and heart disease or heart failure. It had 267 users and couldn't rule out a risk as large as the abstract's. ⁴

A 5 or 10 mg gummy is a normal dose

Common on the shelf, and above the doses the guideline evidence used. The trials behind the American Academy of Sleep Medicine's insomnia guideline used 2 mg, and so does the prescription product sold in Europe. Of 464 US melatonin labels we read, the median serving is 3 mg, 45% are 5 mg or more and 19% are 10 mg or more. ⁶

The label may be off as well. When 25 melatonin gummies sold in the US were tested, they held 74% to 347% of the melatonin on the label, and 22 were off by more than 10%. ⁷

If a patient saw the headline

The abstract doesn't show that melatonin causes heart failure, and it says little about melatonin bought over the counter. A year of nightly use is still worth a conversation. The American Academy of Sleep Medicine suggests clinicians not use melatonin for chronic insomnia, a weak suggestion based on very low-quality evidence that it helps. ⁸

Its strong recommendation for chronic insomnia is cognitive behavioral therapy. ⁹

If they keep taking it, the lowest dose that works is reasonable, and blood thinners and epilepsy call for closer supervision. Write it in the chart: the study could only count the melatonin someone had recorded. ¹⁰

The melatonin monograph covers the sleep trials, the doses studied and the interactions.