Written by Sheila McAdoo, PharmD | Reviewed by Christina Aungst, PharmD Published on June 13, 2022
Key takeaways:
- Melatonin is a hormone that regulates your sleep-wake cycle. It’s commonly available as a dietary supplement.
- Daytime sleepiness is the most common side effect people experience while taking melatonin. Other potential side effects include sleep changes, headache, and dizziness.
- Melatonin side effects are typically mild and temporary. Contact your healthcare provider if your side effects become severe or don’t go away.
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Getting a full night’s sleep can be challenging for many people. In fact, up to 50% of U.S. adults have sleeping problems every now and then. Life’s stressors, poor sleep habits, and several medical conditions can all contribute to a late night under the covers.
When this happens, there’s a term for it that you’ve likely heard of — insomnia. Insomnia refers to a few sleep issues, such as difficulty falling asleep, staying asleep, or a combination of both. Chances are you’ll experience insomnia at least once in your life. Luckily, some medications are available that can help you snooze a bit better.
If you have trouble sleeping, you’ve likely looked at over-the-counter (OTC) products to help you sleep. Melatonin is a popular OTC dietary supplement that is used as a sleep aid.
In this article, we’ll discuss the most common melatonin side effects, and what to do if you experience them.
What is melatonin?
Melatonin is a hormone that your brain naturally makes in response to darkness. It acts as a messenger that tells the rest of your body that it’s time to sleep.
Melatonin is found in nature, but it can also be made in a lab as a dietary supplement. Melatonin supplements are commonly taken for jet lag, sleep disorders, and anxiety around surgery. Melatonin supplements are available as pills, gummies, liquids, and more.
However, even though melatonin naturally plays an important role in sleep, melatonin supplements are not officially recommended as a treatment for insomnia. This is due to lack of evidence that they’re effective. Still, they’re often used by many people for this purpose.
How does melatonin work?
Melatonin helps you regulate when you go to sleep and when you wake up. This sleep-wake cycle is also known as your circadian rhythm.
There are melatonin receptors (chemical binding sites) all throughout your body. These receptors get messages to perform a certain task. For example, when it gets dark, your brain makes more melatonin which sends a message to your body that it’s time to sleep. As the sun comes up, your brain sends out less melatonin, allowing your body to wake up.
In addition to regulating your sleep, melatonin is also an antioxidant that can help protect your cells and assists in regulating other bodily functions. Current research suggests that melatonin may potentially play a role in cancer prevention, heart disease, metabolism disorders, and more.
5 melatonin side effects you should know about
Even though melatonin is a natural hormone, taking it as a supplement can have some side effects. Current research suggests that short-term side effects of melatonin are typically mild. Information on long-term safety of melatonin is limited. Before taking melatonin, speak with your healthcare provider or pharmacist to make sure it’s safe for you to take.
Here’s a quick summary of common short-term side effects you may experience while taking melatonin:
1. Daytime sleepiness or grogginess
The popular use of melatonin is to make you sleep. However, this sleepiness can carry on into the following day. Daytime sleepiness is when you feel the need to fall asleep despite wanting to be awake. This is the most common side effect people experience when taking melatonin.
Because you still want to sleep, you may feel irritable or agitated. To prevent daytime sleepiness or feeling groggy, make sure you only take melatonin in the evening or in the hours before bed.
2. Sleep changes
Since you’re supplementing your body’s natural melatonin levels, you may experience changes in your sleeping patterns. According to the CDC, your brain begins producing more melatonin up to 2 hours before your typical bedtime, with peak levels developing between 2AM and 4AM. By taking additional melatonin at the wrong time, you could shift the timing of your current sleep-wake cycle. It’s also possible that taking melatonin at the wrong time will cause the supplement not to work.
3. Headache
Some people have experienced headaches after taking melatonin. These headaches can be triggered by a high dose or sensitivity to melatonin. However, headaches are also a possible symptom of insomnia.
4. Dizziness
Dizziness is another common side effect of melatonin. The exact reason why isn’t fully known, but one possibility is related to blood pressure changes. Some studies suggest that melatonin may lower blood pressure at night. People who take melatonin, especially those already on high blood pressure medication, may feel light-headed if their blood pressure gets too low.
5. Stomach upset
You may feel stomach discomfort when you take melatonin. Melatonin can cause symptoms like nausea or stomach cramps. If your stomach discomfort worsens while taking melatonin, contact your healthcare provider.
What can I do to manage melatonin side effects?
Experiencing side effects can be frustrating, especially when they’re from a dietary supplement, like melatonin. Thankfully, melatonin’s most common side effects are usually mild and can be easily managed.
When you do experience side effects from melatonin, the chances of them happening depends on the dose you take, so use it with caution. It may be a good idea to start at a low dose of melatonin, and then go up if needed. Melatonin supplements are available in strengths ranging from 1 mg to 12 mg per dose.
If you’re experiencing side effects after taking melatonin, you can consider adjusting your dose. Melatonin strengths of 10 mg or higher can cause more side effects. There is no official recommended dosage of melatonin, so finding the right dose for you may take some trial and error.
Still, stomach discomfort is common in the first few days after starting an oral melatonin supplement. This normally goes away after a few days, so you may be able to wait it out. You could also try another form of melatonin that’s less likely to cause stomach upset, like sublingual melatonin. And if you develop a headache while taking melatonin, OTC pain relievers like ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) may help.
However, it’s important to note that melatonin dietary supplements aren’t officially regulated by the FDA for safety and effectiveness. It’s possible for doses to be slightly different than what’s labeled on their packaging. One study found that more than 70% of the time the melatonin’s labeled doses were significantly different compared to what was labeled.
When should I contact my healthcare provider about melatonin side effects?
As mentioned earlier, melatonin side effects are normally mild and temporary. If any of these side effects become severe or don’t go away, you should contact your healthcare provider for guidance.
The bottom line
Melatonin is generally considered safe to use, and it typically doesn’t cause many side effects. The most common side effects of melatonin are daytime sleepiness and sleep changes. Other side effects include headache, dizziness, and stomach upset. While these side effects are usually mild, you should contact your healthcare provider if they become serious or unmanageable.
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