Is Melatonin Safe Long-Term? A Sleep Physician Explains

Key takeaways:

• Melatonin is a hormone, not a regular supplement. It regulates your sleep-wake cycle, and taking it nightly may come with risks that aren't well understood yet.

• Most people are taking far more melatonin than research supports. Effective doses are closer to 0.5 to 1 mg, not the 5 to 20 mg sold on store shelves.

• Long-term, high-dose use may interfere with your body's ability to make its own melatonin and could affect your metabolism.

• Non-hormonal sleep support options exist that don't carry the same concerns.

You've probably seen melatonin at every pharmacy, grocery store, and gas station checkout counter. It comes in gummies, tablets, liquids, and even kids' vitamins. And because it's sold over the counter without a prescription, most people treat it like any other supplement.

But melatonin isn't like taking vitamin D or magnesium. It's a hormone, and regularly taking a hormone at doses much higher than what your body naturally makes is something worth looking at more closely.

As a physician board-certified in sleep medicine, obesity medicine, and internal medicine, I've spent the last 15 years working with patients who struggle with sleep. Many of them show up already taking melatonin for insomnia, and most were never evaluated for a sleep disorder. They just couldn't sleep, so they reached for the easiest option available.

What does melatonin actually do?

Your brain produces melatonin on its own. A small gland called the pineal gland releases it, and its job is to signal your brain that it's time to wind down for sleep.

It peaks in the middle of the night and drops off toward morning. That's why melatonin is sometimes called the "darkness hormone." It doesn't make you unconscious or knock you out. It just nudges your internal clock toward sleep mode. 

Melatonin is most useful when the issue is sleep timing, like jet lag, shift work, or a delayed sleep schedule. If you're lying awake at 2 a.m. because your mind won't shut off, melatonin probably isn't addressing the actual problem.

A review of clinical trials backs this up. Melatonin only helped people fall asleep about 7 minutes faster and added about 8 minutes of total sleep compared to a placebo. For most people dealing with insomnia, that's barely noticeable.

Why are so many people taking too much?

Walk down the supplement aisle, and you'll see melatonin in 5, 10, even 20 mg doses. Your body doesn't come close to producing that much.

Over the course of a night, your pineal gland makes roughly 0.1 to 0.8 mg of melatonin. A standard 5 mg supplement is already 6 to 50 times that amount.

Studies suggest that 0.5 to 1 mg is the effective range for most adults. Higher doses don't seem to work better. They can actually make things worse:

• Morning grogginess that sticks around for hours

• Vivid or unsettling dreams

• A foggy, "hangover" feeling that drags through the day

I see this pattern with patients constantly. A patient typically will start at 3 mg. It works for a few weeks, then stops. So they bump up to 5. Then 10. Then 15. Each increase gives a short improvement before it fades.

But this isn't tolerance, the way it works with prescription medication. More often, the sleep issue was never about melatonin levels in the first place. Taking more of something that wasn't the right fix doesn't make it work better.

On top of that, melatonin isn't regulated the way prescription drugs are. A 2017 study tested a range of melatonin supplements and found that the actual content varied by as much as 478% from the label. Some products even contained serotonin, a neurotransmitter that shouldn't be in a sleep supplement at all.

Also Read: There Might Be More to Your Melatonin Than You Think—Here’s an Alternative

Can long-term use affect your body's own melatonin?

This is a question I get a lot. And the honest answer is that we don't have enough long-term data to say for sure. But there are reasons to be careful.

Whenever you supplement with a hormone over a long stretch, there's a chance your body starts to reduce its own production. With melatonin:

• High doses may slow down how much your pineal gland produces on its own

•  Your melatonin receptors may become less responsive with prolonged nightly use

• Large-scale studies that would confirm or rule this out haven't been done yet

More sleep specialists are now recommending that people avoid using melatonin long-term. Short-term use for jet lag or a few difficult nights is generally fine. Taking it every single night for months is a different situation.

Newer research adds to the concern. A 2025 preliminary study presented at the American Heart Association followed over 130,000 adults with insomnia. People who took melatonin for at least a year had a 90% higher risk of heart failure and were more than three times as likely to be hospitalized for it.

That doesn't mean melatonin caused those outcomes directly. The link may reflect undertreated insomnia more than anything. But it does highlight how little long-term safety data exists for something millions of people take every night.

Also Read: Want a Healthier Heart? The AHA Says Add Sleep to Your Daily Habits

Does melatonin affect your metabolism?

Most people think of melatonin as a sleep-only hormone. But melatonin receptors show up all over your body, not just in the brain. They're in places that directly affect how you process food and manage energy:

• Your pancreas, where insulin is made

• Fat tissue, which is involved in energy storage and inflammation

• Your liver, which handles blood sugar and fat metabolism

This matters because research shows melatonin plays a role in blood sugar regulation, insulin sensitivity, and energy balance. Some people carry gene variants in their melatonin receptors that are tied to a higher risk of type 2 diabetes.

In animal studies, disrupting melatonin signaling leads to problems with blood sugar control. Restoring normal levels corrects it.

So when someone takes 10 or 20 mg of melatonin nightly, those doses aren't just acting on sleep. They're reaching metabolic receptors at concentrations the body was never designed to handle on an ongoing basis.

A 2024 study found that high-dose melatonin reduced insulin sensitivity in human fat tissue. Separate research showed it changed how the body processed glucose after an evening meal.

At low doses for short-term use, none of this is likely to be an issue. But for anyone managing their weight, blood sugar, or metabolic health, layering a nightly high-dose hormone on top of that is worth thinking about carefully. This is where my obesity medicine background gives me a different perspective than most sleep doctors, and it's a conversation most supplement brands skip entirely.

Why does melatonin cause morning grogginess?

If you've ever woken up feeling heavy, foggy, and slow after taking melatonin, you're not imagining it.

Regular melatonin has a half-life of about 40 to 60 minutes. It clears your system fairly quickly. But many popular products use extended-release formulations designed to keep levels elevated all night. Pair that with the high doses most people take, and melatonin can still be circulating well above normal when your alarm goes off.

Your body is getting a "stay asleep" signal at the exact moment it should be switching to "wake up."

Over time, this can also shift your sleep schedule in the wrong direction if the dose or timing is off. That means it gets harder to fall asleep and harder to wake up.

Also Read: What Happens to Your Body When You Take Melatonin Every Night

What should you try instead?

If melatonin isn't the right fit for most people, what actually works?

The first step is always figuring out what's actually disrupting your sleep. For many people, the answer isn't a melatonin supplement.

Cognitive behavioral therapy for insomnia (CBT-I) is the gold standard treatment for chronic insomnia. It targets the habits and thought patterns that keep people awake. The results tend to last longer than any melatonin supplements. I recommend it regularly.

• Every day sleep habits also go a long way:

• Stick to the same sleep and wake times, even on weekends

• Get morning sunlight to help set your internal clock

•  Wind down before bed with breathing exercises, journaling, or meditation

• Cut off caffeine, alcohol, and heavy meals well before bedtime

If you want supplement support without the concerns that come with melatonin, look for ingredients that work through non-hormonal pathways. That's the approach behind Sip2Sleep®, which I formulated with two plant-based ingredients:

Montmorency tart cherry extract contains melatonin naturally, but at levels much closer to what your body produces on its own. It also contains compounds that support your body's natural production of serotonin and melatonin by slowing the breakdown of tryptophan. You're working with your body's own process instead of overriding it.

Venetron® (rafuma leaf extract) is a Japanese botanical that supports GABA and serotonin activity in the brain. It helps calm the anxiety and mental restlessness that often fuel insomnia, something melatonin doesn't address. It's also been shown to increase time spent in deep sleep, the stage where your brain clears out waste linked to long-term cognitive decline.

References

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2.     Foley HM, Steel AE. Adverse events associated with oral administration of melatonin: a critical systematic review of clinical evidence. Complement Ther Med. 2019;42:65-81.

3.     Erland LA, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med. 2017;13(2):275-281.

4.     Nnadi E, et al. Long-term use of melatonin supplements to support sleep may have negative health effects. American Heart Association Scientific Sessions 2025. Preliminary research.

5.     Owino S, Buonfiglio DDC, Tchio C, Tosini G. Melatonin signaling a key regulator of glucose homeostasis and energy metabolism. Front Endocrinol. 2019;10:488.

6.     Cipolla-Neto J, Amaral FG, Afeche SC, Tan DX, Reiter RJ. Melatonin, energy metabolism, and obesity: a review. J Pineal Res. 2014;56(4):371-381.

7.     Zambrano C, et al. Melatonin decreases human adipose tissue insulin sensitivity. J Pineal Res. 2024;76(5):e12965.

8.     Al Khatib HK, et al. The effect of melatonin on glucose tolerance, insulin sensitivity and lipid profiles after a late evening meal. J Nutr Sci. 2022;11:e7.

9.     Losso JN, et al. Pilot study of the tart cherry juice for the treatment of insomnia and investigation of mechanisms. Am J Ther. 2018;25(2):e194-e201.