Is it safe

Is melatonin bad for your heart?

By GyroscopeUpdated November 14, 20266 sources

That hasn’t been shown. The heart failure headline came from a 2025 conference abstract, not peer reviewed, in which 4.6 percent of long-term melatonin users with insomnia had heart failure within five years, against 2.7 percent of non-users. It couldn’t tell melatonin apart from worse insomnia. We checked on November 14, 2026, and it still hadn’t been published in a journal.

On November 3, 2025, the American Heart Association put out a press release ahead of its yearly meeting, and headlines linking long-term melatonin to heart failure followed. The same release printed a list of the study’s limits, and they change the picture.

We don’t think this study shows melatonin harms the heart. If you take it every night for months, though, it’s a fair moment to ask why you need it, and to check whether it’s doing anything with a two-week test.

It’s like noticing that people who carry umbrellas get wet more often. They carry umbrellas because it’s raining.

What the study did

The researchers searched a large international database of health records for adults with long-term insomnia. Anyone with melatonin in their records for 12 months or more went in the melatonin group, 65,414 people. They were matched with the same number of people with insomnia who never had melatonin recorded, for 130,828 in all, and followed for five years.

The limits, from the same press release

The American Heart Association’s own release lists them:

• It was an abstract, which isn’t peer reviewed, and the findings were called preliminary.
• Melatonin counted only if it was written in someone’s medical record. In the US you buy it over the counter, so many people taking it would have landed in the “no melatonin” group.
• The database mixed countries where melatonin needs a prescription, such as the UK, with countries where it doesn’t, such as the US.
• The researchers had no information on how bad each person’s insomnia was, or on depression, anxiety and other conditions.
• It can show a link, and it can’t show that melatonin caused anything.

The insomnia point is the big one. People who take melatonin for a long time tend to have worse sleep, more depression and anxiety, and more visits to the doctor. The authors of a 2026 Open Heart paper point out that this can make a sleep aid look harmful in health records even when it isn’t the cause.

What’s been found since

A 2026 study in the journal Open Heart looked at US national survey data from 1999 to 2018. Melatonin users were quite different from non-users from the start, mostly in sleep trouble and depression. After adjusting for that, recent melatonin use wasn’t significantly linked to heart disease or heart failure. The authors were careful to say that doesn’t prove it’s safe either. A 2026 review in the World Journal of Experimental Medicine described the original finding as a single, unpublished abstract that hadn’t been peer reviewed or checked independently.

Where melatonin and the heart do meet

One interaction has been measured. In a 2000 trial, 47 people whose blood pressure was well controlled on nifedipine took 5 mg of melatonin or a placebo at 10:30pm for 4 weeks. On melatonin their systolic blood pressure ran about 6.5 points higher and their heart rate rose too. If you take blood pressure medicine, ask your prescriber before you start, and measuring at home for a week is a good way to see your own numbers.

In the short trials, palpitations showed up only rarely as a side effect. Across 37 trials, most side effects were mild, but most of those trials lasted 4 weeks or less, so years of nightly use haven’t been studied well in either direction. Can you take melatonin every night? covers that part.