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

How long can you safely take melatonin?

There isn’t a set number of weeks or months when melatonin suddenly becomes unsafe. Most research focuses on short-term use, while fewer studies have followed people taking melatonin continuously for years.

How long you use it also depends on why you started. Taking melatonin temporarily for jet lag or a disrupted sleep schedule is different from needing it every night because you continue to have trouble sleeping.

If melatonin has been part of your routine for months or years, it may be worth discussing with your healthcare provider whether you still need it and whether the sleep problem that led you to start taking it has been addressed.

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. 

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

Do you need melatonin if you have insomnia?

If you regularly have trouble falling asleep or staying asleep, finding the reason for the insomnia is usually more useful than continuing to increase a melatonin dose.

Cognitive behavioral therapy for insomnia (CBT-I) is the recommended first treatment for chronic insomnia. It addresses the behaviors and thought patterns that can keep poor sleep going and has stronger evidence for chronic insomnia than melatonin supplements. 

Other sleep problems may need a different approach. Sleep apnea, restless legs syndrome, circadian rhythm disorders, medication side effects, stress, and mental health conditions can all affect sleep, and treatment depends on what is causing the problem.

This is one reason I encourage patients to think beyond whether a sleep product makes them drowsy. If you continue to struggle with sleep despite taking something every night, that is useful information about the sleep problem itself.

Who should be more careful with long-term melatonin use?

Regular melatonin use deserves additional consideration if you take certain medications or have health conditions that could affect how your body responds to it.

Talk with a healthcare provider before using melatonin regularly if you:

• Take blood thinners or other medications that may interact with melatonin
• Have epilepsy or a seizure disorder
• Are pregnant or breastfeeding
• Are considering long-term melatonin use for a child or teenager
• Take several prescription medications

Older adults may also be more sensitive to lingering sleepiness or dizziness, particularly with higher doses.

If you take prescription medications, your doctor or pharmacist can also help check whether melatonin could interact with anything you already use.

Also Read: Melatonin Withdrawal: Is It Real, and What Happens When You Stop Taking It?

Is there a better alternative to melatonin?

Some people do well with occasional melatonin and have no reason to change what they are doing. Others would rather support sleep without making a synthetic melatonin supplement part of their nightly routine.

Maintaining good sleep hygiene is a good place to start. To support a healthy sleep-wake cycle, try to keep consistent sleep and wake times. Ensure you get exposure to natural light during the day, limit caffeine intake later in the day, and allow yourself time to relax before bedtime.

For people who also want natural sleep aids without adding synthetic melatonin, that is the approach I took when developing Sip2Sleep®.

Sip2Sleep® combines Montmorency tart cherry extract and Rafuma leaf, two plant-based ingredients that have been studied for their effects on sleep.

Montmorency tart cherry naturally contains a small amount of melatonin along with other plant compounds. It has been studied for its sleep-supporting benefits, with research showing improvements in sleep duration and sleep quality. 

Rafuma leaf, also known as Apocynum venetum, has also been studied in humans. Research using the leaf extract found improvements in sleep, including increased non-REM sleep time. 

Sip2Sleep® contains no added synthetic melatonin, which gives people another option when they want nightly sleep support without relying on a conventional melatonin supplement.

[Try Sip2Sleep®]

What do we know about long-term melatonin safety?

Most of the evidence we have on melatonin safety comes from shorter periods of use. Longer studies have generally been reassuring, but there are still fewer high-quality studies following people who take melatonin every night for several years.

That means researchers have not identified widespread serious problems from long-term use, but they also cannot say that every dose or pattern of prolonged use has been fully studied.

This is one reason I look at long-term melatonin use differently from occasional use. The longer someone relies on it, the more useful it becomes to ask why they still need it and whether the underlying sleep problem is being treated.

About the author

Dr. Ruchir P. Patel, MD, FACP, is the Medical Director of the Insomnia and Sleep Institute of Arizona and the founder of Sip2Sleep. He is triple board-certified in sleep medicine, obesity medicine, and internal medicine. Dr. Patel is a multi-year Phoenix Magazine Top Doctor and holds the Inspire Excellence designation.

References

1.     Fatemeh G, Sajjad M, Niloufar R, et al. Effect of melatonin supplementation on sleep quality: a systematic review and meta-analysis of randomized controlled trials. J Neurol. 2022;269:205-216.

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.

10. Losso, J. N., Finley, J. W., Karki, N., Liu, A. G., Prudente, A., Tipton, R., Yu, Y., & Greenway, F. L. (2018). Pilot Study of the Tart Cherry Juice for the Treatment of Insomnia and Investigation of Mechanisms. American journal of therapeutics, 25(2), e194–e201. https://doi.org/10.1097/MJT.0000000000000584.

11. Yamatsu, A., Yamashita, Y., Maru, I., Yang, J., Tatsuzaki, J., & Kim, M. (2015). The Improvement of Sleep by Oral Intake of GABA and Apocynum venetum Leaf Extract. Journal of nutritional science and vitaminology, 61(2), 182–187. https://doi.org/10.3177/jnsv.61.182