If you occasionally — or regularly — pop a melatonin supplement to help you sleep, you are far from alone. It’s estimated that at least 5 million adults and 4 million children in the U.S. do the same.
And while some swear by melatonin for improving sleep and treating insomnia, some experts worry about potential risks, including heart failure. Learn how to manage the pros and cons of melatonin use.
What is melatonin?
Melatonin is a hormone naturally produced by the body and released based on external cues. As it gets dark outside, your body releases more melatonin, and when it’s lighter, your body releases less. When your brain registers an increase in melatonin, that’s your body’s signal to start getting sleepy.
People often take supplemental melatonin to crank up the hormone’s sleep-enhancing effects. In the US, melatonin is available as an over-the-counter dietary supplement. You’ll find it in tablets, gummies and liquids.
Research is mixed, but there’s some evidence that taking melatonin can help alleviate jet lag symptoms and help you fall asleep faster.
What the science says about melatonin and heart failure
A 2025 study, published in the American Heart Association journal Circulation, raised a red flag about the possible connection between long-term melatonin use and risk of heart failure. The researchers reviewed health records from more than 130,000 adults who had been diagnosed with insomnia. Those who’d been prescribed melatonin and used it regularly for a year or more had a significantly increased incidence of heart failure compared to those who didn’t use melatonin.
The researchers concluded that melatonin use was “associated with an 89% higher hazard of incident heart failure, a three-fold increase in heart failure-related hospitalizations and a doubling of all-cause mortality.”
As scary as those findings sound, it’s important to put them in perspective. A study of this design can only show a relationship between melatonin and rates of heart failure. It does not prove that one causes the other. In fact, the study does not draw any definitive conclusions as to why that connection was so strong.
The researchers also acknowledge that there are several other factors that may have influenced those findings. The database they pulled from included people in countries (such as the UK) where melatonin is available only by prescription as well as the US, where it does not require a prescription. That means that anyone who didn’t have a prescription for melatonin would be counted in the “non-melatonin group,” even if they routinely took an over-the-counter version.
This type of study also doesn’t account for other factors — such as mental health or obesity — that may impact both insomnia and heart health. It’s possible that the increased risk of heart failure is related to other health or lifestyle factors and not the melatonin supplements.
Side effects of melatonin
Most research has looked at short-term use of melatonin for occasional insomnia or jet lag. It is generally considered safe for those uses.
But even when used only occasionally, melatonin can have some side effects. These include:
- Daytime drowsiness
- Dizziness
- Headache
- Nausea
How to use melatonin safely for sleep
Because melatonin is considered a dietary supplement in the US, and not a drug, it’s not tightly regulated. That means it can be hard to know how much of the hormone you’re taking. One study, published in the Journal of the American Medical Association, analyzed the amount of melatonin in 25 over-the-counter products. Researchers found that “the actual quantity of melatonin ranged from 74% to 347% of the labeled quantity.”
Although it’s no guarantee, you should look for melatonin supplements manufactured by reputable brands. Labels that display the “USP Verified” mark mean the supplement meets the standards of the U.S. Pharmacopeial Convention.
Always use the smallest effective dosage and take it only for short periods of time as needed.
Talk to your doctor about taking melatonin for sleep
Whether you have occasional difficulty sleeping or diagnosed insomnia, you should talk to your doctor about your concerns. And because melatonin has the potential to interact with some other medications (including those for birth control and high blood pressure) it’s important your doctor knows if you’re taking it.
Sometimes, sleep issues are a sign of other, more serious health problems. If necessary, your doctor can refer you to a sleep specialist. They can diagnose underlying conditions affecting your sleep and help you get the rest you need.
