Melatonin at Bedtime Barely Helps. 3 Hours Earlier Works Better

Melatonin is one of the most popular sleep aids in the world. Most people take it the same way: a pill or gummy, half an hour before bed.

A 2024 review of 26 trials suggests that may be the weakest way to take it.

Here’s what melatonin can and can’t do, how much to take, when, and what we know about safety.

Does melatonin work for adults?

Yes, but only a little. Across the trials, people fell asleep about 9 minutes faster and slept about 20 minutes longer than with a dummy pill.

That’s real, but modest. Talking therapy for insomnia, called CBT-I, cut the time to fall asleep by about 19 minutes in one review.

Melatonin is a hormone your brain makes when it gets dark. It tells your body that night has come, rather than knocking you out like a sleeping pill.

That’s why big sleep groups are cautious. The American Academy of Sleep Medicine suggested in 2017 that doctors not use melatonin for long-term insomnia.

It called that a weak recommendation, meaning the evidence was uncertain. The US National Institutes of Health (NIH) says it may help with jet lag and some other sleep problems.

What the research shows

A review of 26 trials

The main source is a 2024 review in the Journal of Pineal Research.

It pooled 26 randomised, double-blind trials published from 1987 to 2020. Each compared melatonin with a dummy pill in adults, with 1,689 observations in total.

Some trials tested healthy volunteers, and others tested people with insomnia.

Doses ranged from 0.1 to 10 mg a day, for 1 to 28 days.

The team asked a practical question: what dose, and what timing, works best?

How much melatonin should I take?

The benefit grew with the dose, then levelled off. It peaked at about 4 mg a day.

Going higher added no extra benefit. That matters, because many shop products contain 5 or 10 mg.

The authors’ conclusion: doses between 2 and 4 mg cover the useful range. They also note that doctors generally advise the lowest dose that works.

When should I take melatonin?

This was the most interesting finding. The earlier people took melatonin before sleep, the faster they fell asleep, up to about 3 hours.

Taking it 1 hour before bed was no better than taking it at bedtime. Taking it 2 or 3 hours before was clearly better.

The team also ran an example through their model. Someone taking 2 mg 30 minutes before bed would get almost no benefit.

The same person taking 4 mg 3 hours before bed would fall asleep about 9 minutes faster. Even 2 mg taken 3 hours before gave about 8 minutes.

So in this model, timing mattered more than dose.

Why timing might matter

Your body starts making its own melatonin about 2 hours before you usually fall asleep. A pill taken earlier may copy that natural rise.

Melatonin also lowers body temperature, which helps sleep. In one study, that drop peaked about 2.5 hours after a dose.

The catch

Here’s what I’d keep in mind. The timing and dose results are predictions from a statistical model, not results from one direct trial.

The trials were small and short, lasting 1 to 28 days. Melatonin also worked less well in people with insomnia than in healthy volunteers.

Only two trials gave melatonin more than 3 hours before sleep. And there were signs that some trials with weak results were never published.

Who funded it

The review was funded by an Italian foundation, the Italian Ministry of Health and donations to an Italian research hospital.

One author co-founded a University of Pisa spin-off company that works in sleep medicine. The others reported no conflicts.

Is it safe to take melatonin every night?

Short-term use

For most adults, short-term melatonin looks safe. The NHS lists mostly mild side effects, such as daytime sleepiness, headache, dizziness and feeling sick.

In the UK, melatonin is prescription only. It’s mainly used for short-term sleep problems in people aged 55 and over, usually for up to 13 weeks.

Long-term use and the heart

Long-term safety is the open question. The NIH says information on long-term use “is lacking”.

In 2025, a study presented at an American Heart Association meeting raised a concern. It looked at health records of 130,828 adults with insomnia.

Over 5 years, people with long-term melatonin use recorded in their records were more often diagnosed with heart failure: 4.6% versus 2.7%.

That sounds alarming, but there are big caveats. This was an observational study, so it can’t prove melatonin caused anything.

People who take melatonin for a year may have worse insomnia, low mood or anxious feelings. Those can raise heart risk on their own.

The study also wasn’t peer reviewed when it was presented. And anyone buying melatonin over the counter would have counted as a non-user.

A 2026 analysis in the journal Open Heart used US national survey data. It found no clear link between recent melatonin use and heart disease or heart failure.

Its authors say neither study proves harm or safety. Better long-term studies are needed.

Labels may be wrong

There’s another problem with shop products. In 2023, researchers tested 25 melatonin gummies sold in the US.

Only 3 contained within 10% of the amount on the label. Actual amounts ranged from 74% to 347% of the label, and one gummy contained no melatonin at all.

Who should be careful

• People with epilepsy or on blood thinners should only take melatonin under medical supervision, the NIH says.
• People with autoimmune conditions, or liver or kidney problems, should check with a doctor first, the NHS says.
• Older people may stay drowsy longer the next day.
• Pregnant or breastfeeding women: there’s little research on safety.

Melatonin for children is a separate question. We covered it in our article on melatonin and kids’ sleep.

What earlier research found

A 2013 review found a similar, small benefit

A 2013 review in PLOS ONE pooled 19 studies with 1,683 people who had sleep disorders, including some children.

Melatonin cut the time to fall asleep by about 7 minutes and added about 8 minutes of sleep. Higher doses and longer trials showed bigger effects.

The authors called the benefit modest. They also found it didn’t seem to wear off with continued use.

A 6-month trial in older adults

A 2010 trial in BMC Medicine tested a 2 mg slow-release melatonin pill in 791 adults aged 18 to 80 with insomnia.

People took it 2 hours before bedtime. In those aged 65 to 80, it cut the time to fall asleep by 19.1 minutes, versus 1.7 minutes with a dummy pill.

The benefit lasted over 6 months, and side effects were mostly mild. The drug’s maker funded the trial, and some authors worked for it.

Jet lag is where melatonin shines

A 2002 Cochrane review found that melatonin reduced jet lag in 9 of 10 trials, for flights crossing five or more time zones.

People took it close to bedtime at their destination. Doses from 0.5 to 5 mg worked about equally well, and higher doses added nothing.

Side effects in 37 trials

A 2019 review in CNS Drugs looked at side effects in 37 trials of melatonin for sleep problems.

The most common was daytime sleepiness, in 1.66% of people. Most side effects were mild and went away quickly.

But most trials lasted 4 weeks or less.

How it fits together

The research agrees on the basics: melatonin gives a small, real benefit, with few short-term side effects.

What we lack is proof of long-term safety.

How much should you trust this?

Promising. Melatonin clearly beat a dummy pill in randomised trials. But the best timing and dose come from a model, not direct tests.

What makes it convincing

• The review pooled 26 double-blind, randomised trials in adults.
• Its results held when the team accounted for trial quality.
• Earlier reviews found a similar, small benefit.

What makes me cautious

• The trials were small and lasted 28 days at most.
• No trial directly compared taking melatonin 30 minutes versus 3 hours before bed.
• Melatonin worked less well in people with insomnia, who are most likely to use it.
• Some trials with weak results may never have been published.

What this means for you

• Try timing before dose. If melatonin isn’t helping, the review suggests taking it 2 to 3 hours before bed, rather than raising the dose.
• Keep the dose low. The useful range in the review was 2 to 4 mg. Higher doses added nothing.
• Plan your evening around it. If you take it early, you may feel sleepy early. Don’t drive if you feel drowsy.
• Use it short term. UK doctors usually prescribe it for 1 to 4 weeks, sometimes up to 13.
• Struggling for months? Ask about CBT-I. It’s the first treatment doctors recommend for long-term insomnia.
• Taking other medicines? Check with a doctor or pharmacist, especially if you take blood thinners or have epilepsy.

The NIH guide to melatonin covers what it may help with and its safety.

For more on sleep, see how much sleep you really need and whether magnesium helps you sleep.

In this short video, Mayo Clinic explains what to consider before taking melatonin for sleep:

What we still don’t know

1. Does earlier timing really work better? A trial should test it directly, in people with insomnia.
2. Is years of nightly use safe? Most trials lasted weeks, not years.
3. Is the heart failure signal real? Only better long-term studies can say.
4. Does it differ by person? Night owls and early birds may need different timing.

My take: right time, small dose

What I like about this review is that it asks a useful question. Not just “does melatonin work?”, but “how do you use it well?”

I’m less convinced by any claim that melatonin is a strong sleep aid. Even at its best, the benefit is modest.

So my reading is simple. If you use it, take a small dose a few hours before bed, and only for a while.

If sleep has been bad for months, melatonin isn’t the answer. Talk to a doctor about CBT-I.