What Are the Side Effects of Melatonin?

Written by Natalie G., Writer

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In This Article

Discover comprehensive information about the safety and potential side effects of melatonin, along with additional tips and insights.

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Melatonin is a hormone that we all naturally produce. Its production increases when it is dark¹, signaling to our bodies that it is time to get sleepy, and it decreases when it becomes light, signaling to our bodies it is time to wake up. 

Melatonin supplements, on the other hand, are created synthetically, and you can take them in the form of capsules, tablets, liquids, gummies, or even patches². These are used to help people sleep³ by helping to regulate their circadian rhythm, the body’s natural sleep-wake cycle. 

Melatonin is generally considered safe to take on a temporary basis, especially if people find it beneficial.¹ However, that doesn’t mean it can’t have side effects. 

Read Our Guide: Melatonin: Everything You Should Know

Side Effects of Melatonin 

Experts consider occasional or short-term melatonin use to be safe for most people, and the risk of side effects is low.^{2, 3} 

That said, there are possible side effects⁴ that can happen when taking melatonin. 

• Daytime fatigue – The most common side effect of melatonin is fatigue in the morning after taking it.⁴ If this happens to you, try lowering your dose and making sure you’re taking it two hours before bed.³ 
• Headache – Melatonin may cause a headache in some people.⁴ To combat this, the National Health Service (NHS) recommends drinking plenty of water if you’re taking melatonin. They also advise avoiding alcohol because it can make you dehydrated and impact the way melatonin works.⁴ 
• Stomach issues – Some people report stomach aches or nausea when using melatonin.⁴ That said, some research has shown that melatonin may be a safe treatment for those with IBS due to its slight pain-relieving effects.² Additionally, its ability to regulate the circadian rhythms of our gut bacteria⁵ could be helpful as well.
• Dizziness – The NHS recommends avoiding driving, cycling, or using any tools or machinery if melatonin has made you dizzy.⁴ Additionally, alcohol will worsen your dizziness, so avoid mixing melatonin and alcohol.⁴ 
• Irritability – Some people report irritability or restlessness when taking melatonin.⁴ If this happens to you, it may very well be because you’re taking too high a dose.² Try lowering your dose, and if this doesn’t work, stop taking melatonin. 
• More vivid or strange dreams – According to the NHS, taking melatonin may lead to more strange dreams.⁴ Supplemental melatonin can increase the amount of time spent in REM sleep⁶, which is the portion of our sleep cycle when vivid dreams are more likely to occur. This means you could be more likely to dream since you’re in REM sleep longer, however, experts say it’s not clear whether melatonin directly causes more vivid dreaming.⁶

Side Effects of Melatonin in Children 

Supplemental melatonin is generally considered safe for kids⁷ as long as the dose is appropriate and any behavioral or environmental issues impacting sleep are also addressed. However, melatonin may affect children differently than adults. 

For example, experts say that melatonin production declines at the onset of puberty⁸. 

Since this drop in melatonin is a natural process before puberty, some experts hypothesize that giving your prepubescent child melatonin could delay puberty, though more research is needed to confirm this.⁸

Children may also be more susceptible to nightmares and vivid dreams with melatonin supplements. Kids naturally spend more time in REM sleep⁹, and as mentioned, taking supplemental melatonin seems to increase the time spent in REM sleep, which is when vivid dreams and nightmares often occur.⁶ 

Other side effects for children taking melatonin are similar to those of adults: headaches, dizziness, mood changes, and morning grogginess.⁷ These side effects should disappear with discontinuation. 

Learn more: A Guide to Melatonin for Kids 

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Melatonin Safety

Before taking any new supplements, we strongly encourage you to consult your healthcare provider. 

When taking melatonin it is important to remember that more is not always better. Some experts advise taking 1 to 3 milligrams two hours before bed.³ That said, this dosage is a general recommendation, and you should discuss dosage with your healthcare provider to ensure you take the proper amount for you. 

Melatonin timing is important because two hours before bedtime is about when your body naturally starts producing melatonin in the absence of artificial light.¹ So to help maximize its effectiveness, you’ll also want to dim the lights and stop looking at screens at about this time.³ 

If lowering the dose and taking it earlier does not mitigate your side effects, you can stop taking melatonin at any time without worrying about weaning off of it¹⁰. Unlike other sleep medications where you need to take more of it over time or experience a “hangover” effect in the morning, melatonin is considered to be non-addictive or habit-forming¹¹. 

However, it’s important to note that because melatonin is sold over the counter in the United States, it is not regulated by the FDA. This means that when you buy your melatonin supplement, you’ll have no real way of knowing how much melatonin (or other ingredients) are actually in the supplement.² 

This is why it is important to buy a melatonin supplement from a high-quality, reputable brand. For example, look for supplements approved by the U.S. Pharmacopeia¹², a third-party organization that helps provide product transparency for consumers. You can look for the words “USP verified” on the label. 

Who Should Avoid Melatonin?

Although this supplement is generally considered safe, certain populations should avoid taking melatonin¹³. 

• Those who have a melatonin allergy – If you’ve ever had an allergic reaction to a supplement containing melatonin or any other medication, you should not take melatonin.¹³ 

• Those with liver or kidney problems – The National Health Service advises against taking melatonin for those with liver or kidney problems¹³ However, there has been research looking at melatonin’s role in potentially healing the liver¹⁴ and kidneys¹⁵, so more information is needed. 

• People with autoimmune disorders – If you have lupus, multiple sclerosis, rheumatoid arthritis, or any other autoimmune condition, you should avoid supplemental melatonin as it may stimulate inflammation.¹³ 

Can You Overdose on Melatonin? 

Let’s quickly clarify the difference between an overdose and a lethal dose. An overdose¹⁶ means you’ve taken too much of something (a “toxic” amount) and are experiencing side effects as a result. A lethal dose means you have taken so much of something that it kills you. 

You can overdose on melatonin, meaning you can take too much of it and experience side effects. The most common side effects of a melatonin overdose¹⁷ are drowsiness, dizziness, headache, fatigue, confusion, bad dreams, hypothermia, tachycardia, and hypotension. 

However, in animal studies, researchers did not find an amount of melatonin that was lethal in at least 50 percent of the test subjects.²

Learn more: Can You Overdose on Melatonin?

When Should You Seek Medical Help? 

More serious melatonin side effects are rare, affecting less than 1 in 1,000 people.⁴ That said, if after taking melatonin you experience changes in your eyesight, feel faint or pass out, start feeling confused, experience vertigo, or have unexplained bruising or bleeding that does not stop, you should discontinue use and call your doctor or 911.⁴ 

In very rare cases, it is possible to have a serious allergic reaction to melatonin, which includes symptoms such as⁴:

• Sudden swelling of the lips, tongue, mouth, or throat
• Struggling to breathe
• Inability to swallow
• The skin, tongue, or lips suddenly turn blue, gray, or pale
• A skin rash that is swollen, itchy, blistered, or peeling
• Sudden confusion, dizziness, or drowsiness
• Fainting and not waking up
• A child going limp, floppy, or not responding as they normally do

If any of these symptoms of an allergic reaction occur after taking melatonin, you should discontinue use and seek emergency medical care. 

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Additional Sleep Tips 

If you either can’t or would prefer not to take melatonin, there are other ways to get better sleep through daily sleep hygiene habits. Many of these can also complement the effects of melatonin supplementation. 

• Increase your melatonin naturally – You can help your body’s natural melatonin production by dimming the lights at night and cutting off screen devices like smartphones and laptops at least one hour before bed.¹ You can also eat more melatonin-boosting foods¹⁸ like eggs, fish, nuts, seeds, legumes, mushrooms, and certain cereals. 
• Establish a regular sleep schedule – Going to bed and waking up at the same time each day can help regulate your circadian rhythm and get your sleep schedule back on track. 
• Practice a nightly routine – Introducing a regular, relaxing nighttime routine can help you wind down before bed and tell your body it’s time to rest. Some great examples of nighttime rituals are baths, reading a book, journaling, meditation, or gentle stretching.
• Create an ideal sleep environment – As we said, your bedroom should be dark to promote melatonin production. However, keeping it cool and quiet can also foster better sleep. Additionally, sleeping on a quality mattress and comfortable bedding can help you feel even more ready for sleep.
• Avoid alcohol at night – Research shows that alcohol negatively impacts sleep¹⁹. Therefore, avoid consuming alcohol at night if you’re having sleep issues. 
• Stop drinking caffeine in the afternoon – You should have your last cup of coffee at least six hours²⁰ before you plan to go to bed since caffeine can stay in your system for up to six hours. 
• Avoid large meals at night – Eating a big meal late at night could negatively impact your sleep, possibly causing discomfort or indigestion. Research shows that eating three hours²¹ or more before bed is ideal.
• Add in regular exercise – Regular exercise has been proven²² to help you fall asleep more quickly and improve overall sleep quality. 
• Limit afternoon naps – Afternoon naps can impact your ability to fall asleep at night. If you do need to take a nap, limit it to 10 to 20 minutes²³ so it won’t negatively impact your sleep that night.
• Try magnesium instead – Magnesium is another supplement that may help with sleep. Just like with melatonin, speak with your healthcare provider before introducing any to your daily routine. 

Learn more: Magnesium vs. Melatonin

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