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The Surprising Side Effects of Melatonin: What You Need to Watch Out For

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August 7, 2023

The Surprising Side Effects of Melatonin: What You Need to Watch Out For

Medically reviewed by: 

Dr. Areti Vassilopoulos

Yale School of Medicine

Medically reviewed by: Dr. Areti Vassilopoulos, Yale School of Medicine

If you're considering taking melatonin as a sleep aid, it's important to know about the potential side effects. There are some unexpected effects that you should be aware of before incorporating it into your routine.

Common Side Effects

Melatonin can cause daytime drowsiness, affecting your alertness and focus during the day.


Mild headaches can be a common side effect of melatonin use. These headaches are typically manageable and may not interfere with daily activities. However, intense migraines can also occur in some individuals, causing severe pain and potential disruptions to daily life. Additionally, some people may experience headaches upon waking up after taking melatonin, which could be accompanied by feelings of agitation or confusion but tend to resolve throughout the day without causing daytime drowsiness.

Dizziness and Drowsiness

Feeling lightheaded and experiencing difficulty concentrating are common side effects of melatonin. These symptoms may lead to agitation and confusion, affecting your daily activities. Another potential side effect is excessive daytime drowsiness, which can impact your productivity and overall well-being. It's important to be aware of these possible outcomes before considering melatonin as a sleep aid.

Nausea and Upset Stomach

Nausea after taking melatonin can be a common side effect that some individuals experience. Along with stomach pain or cramping, it can lead to discomfort and agitation. Additionally, some people may wake up with a 'hangover' feeling in the morning, which can include confusion and daytime drowsiness.

  • Nausea after taking melatonin
  • Stomach pain or cramping
  • Hangover feeling in the morning (confusion, daytime drowsiness)

Less Common Side Effects

Sleep Disturbances

Nightmares can disrupt your sleep and leave you feeling anxious and unsettled. These vivid dreams can jolt you awake, making it difficult to fall back asleep. Insomnia, on the other hand, can prevent you from getting a good night's rest altogether.

Mood Changes

Mood changes can be a potential side effect of melatonin, causing feelings of sadness and hopelessness. It's important to be aware that this supplement may not always have the desired positive impact on your mood.

Anxiety is another possible result of taking melatonin. You may experience heightened feelings of unease or worry, potentially interfering with your daily activities and well-being.

Irritability can also arise from melatonin use, causing you to become easily agitated or impatient in various situations. It's crucial to consider how this side effect might affect your relationships and overall quality of life when deciding whether or not to take melatonin.

Rare Side Effects

Sleepwalking and other parasomnias are rare but potential side effects of melatonin. While melatonin is often used to improve sleep quality, it can sometimes lead to unusual behaviors during sleep, such as sleepwalking or night terrors. It is important to be aware of these possibilities before starting melatonin supplementation.

Allergic reactions can occur in some individuals who take melatonin. Symptoms may include rash, itching, swelling, or difficulty breathing. If you experience any signs of an allergic reaction after taking melatonin, it is crucial to seek medical attention immediately.

It's important to be aware of these potential side effects when considering taking melatonin as a sleep aid to help you make an informed decision about incorporating melatonin into your nighttime routine. It is also worth noting that since melatonin is considered a supplement, contents are not regulated by the FDA so the exact components of your over-the-counter melatonin might vary.

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Disclaimer: The information provided on this page should not be taken as medical advice and should not replace the advice of your healthcare provider. Always consult your physician before taking any new medication(s) or altering your current dosage.

If you are experiencing suicidal thoughts, please contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support.

Dr. Areti Vassilopoulos

Dr. Vassilopoulos is the Clinical Content Lead for Sleep Reset and Assistant Professor at Yale School of Medicine. She has co-authored peer-reviewed research articles, provides expert consultation to national nonprofit organizations, and chairs clinical committees in pediatric health psychology for the American Psychological Association. She lives in New England with her partner and takes full advantage of the beautiful hiking trails.