Melatonin is easily one of the most popular sleep supplements around.
Not only that, but most people see it as a natural and safe option they can pop without a second thought. Millions of us routinely take a tablet to fight off jet lag or get through a stressful week, treating it like a harmless alternative to heavy prescription pills. However, fresh research is starting to raise some serious questions about what happens when taking it stops being an occasional fix and turns into a permanent nightly habit.
While it’s brilliant for resetting your body clock in a pinch, relying on a daily dose might actually be messing with your body’s natural chemistry and masking bigger issues. If you’ve got into the habit of taking it every single evening, looking at what the science actually says about long-term use is pretty eye-opening.
What is melatonin and what does it do?
Melatonin is a hormone the brain produces naturally to help regulate the body’s internal clock, signalling that it’s time to wind down and sleep. Taking a supplement version of this hormone at the end of the day can help people fall asleep more easily, particularly those who struggle with insomnia or disrupted sleep patterns.
In the UK, melatonin is only available on prescription. In the US and many other countries, it can be bought over the counter without any medical guidance on how much to take or for how long, which means many people use it for months or years without any professional input.
A new study found a link between melatonin use and heart health.
Researchers analysed health records from more than 130,000 adults across multiple countries, comparing those who had been prescribed melatonin for over a year with those who hadn’t been prescribed it at all. The results were unexpected enough to catch attention in the scientific community.
Those taking melatonin long-term were found to have an 89% higher risk of heart failure over the following five years, and were around twice as likely to die from any cause during that period. A separate part of the analysis found that those on melatonin for over a year were almost three and a half times more likely to be hospitalised for heart failure compared to those not taking it.
The findings need to be treated carefully.
The research hasn’t yet been through the full peer review process that science typically uses to verify findings, which means it should be treated as preliminary rather than conclusive. The study also has a notable limitation that affects how the results can be interpreted.
Participants weren’t directly asked about their melatonin use. Instead, researchers used prescription records, which means the comparison group of people not prescribed melatonin may have included people in the US who were buying it over the counter without a prescription and taking it anyway. This makes the comparison between groups less reliable than it would otherwise be.
Scientists are still taking it seriously.
Despite the limitations, researchers involved in the work and independent experts who reviewed it agreed that the pattern of findings was consistent and noteworthy enough to warrant a real follow-up investigation. The increases in risk were large enough that they’re hard to dismiss, even accounting for the study’s methodological weaknesses.
The concern isn’t that melatonin is definitely causing harm, but that nobody currently knows whether it is or isn’t when used over a long period of time. That gap in knowledge is itself the problem, given how widely and casually the supplement is taken.
What we do and don’t know about long-term use
Melatonin is generally accepted as safe for short-term use, typically meaning around one to two months for adults who aren’t pregnant or breastfeeding. Beyond that window, the research is thin, and comprehensive studies on long-term effects simply haven’t been done at the scale needed to draw firm conclusions.
Some existing studies suggest longer-term use is safe, but these aren’t definitive. The growing popularity of melatonin as an everyday supplement means this knowledge gap is becoming more pressing, since more people than ever are taking it regularly without clear guidance on when to stop.
The broader picture of how melatonin is used needs to be examined.
Part of what makes melatonin so widely used is the perception that anything described as natural is automatically safe. Being derived from a hormone the body already produces makes it feel less like a drug and more like a top-up, which reduces the caution people apply to it compared to other sleep medications.
The reality is that natural origin doesn’t guarantee safety, particularly when used in supplement doses over extended periods. There have also been concerns raised separately about the safety profile of melatonin products for children, following a series of non-fatal overdose cases in Australia.
What does this mean if you currently take melatonin?
The research doesn’t change current health recommendations, and nobody is suggesting people should stop taking melatonin immediately based on these findings alone. What it does suggest is that treating melatonin as something you can take indefinitely without thinking about it may not be the best approach.
If you’ve been taking melatonin regularly for more than a couple of months, it’s worth having a conversation with a doctor rather than simply continuing without review. The supplement market moves faster than research can keep up with, and getting medical guidance on dose and duration is a sensible step for anyone using it as a regular fixture in their evening routine.
