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Side Effects of a Melatonin Overdose

author image Rae Uddin
Rae Uddin has worked as a freelance writer and editor since 2004. She specializes in scientific journalism and medical and technical writing. Her work has appeared in various online publications. Uddin earned her Master of Science in integrated biomedical sciences with an emphasis in molecular and cellular biochemistry from the University of Kentucky College of Medicine.
Side Effects of a Melatonin Overdose
A melatonin overdose may cause severe drowsiness. Photo Credit Blaj Gabriel/iStockphoto/Getty Images

Melatonin supplements are a synthetic version of the naturally occurring hormone melatonin, which helps regulate your body's sleep-wake cycle. Taking appropriate doses of melatonin may help alleviate issues associated with sleeping problems, such as insomnia and jet lag, according to MedlinePlus. Before taking this supplement, discuss the side effects of a melatonin overdose with your medical provider.


Severe drowsiness may occur if you take an unusually large dose of melatonin, Drugs.com warns. This supplement is typically used to induce sleep and may affect your ability to remain attentive or focused during your daily activities. Excessive drowsiness may cause you to fall asleep shortly after treatment and you may remain asleep for several hours.

Upset Stomach

High doses of melatonin may irritate your digestive tract. Consequently, you may experience stomach irritation, nausea or vomiting following an overdose of melatonin. These side effects may also contribute to a decrease in your normal appetite. Consult a doctor as soon as possible if you experience severe stomach discomfort or persistent vomiting after taking melatonin.


Headache pain may arise following an overdose of this supplement. This side effect may interfere with your ability to focus on daily tasks and can exacerbate sensations of drowsiness or fatigue. If you develop sudden or severe headache pain after taking melatonin, seek care from your primary medical provider.

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