More threads by David Baxter PhD

David Baxter PhD

Late Founder
Melatonin side effects: What are the risks?
by Brent A. Bauer, M.D., Mayo Clinic
Oct. 20, 2011

Is melatonin a helpful sleep aid - and what should I know about melatonin side effects?

The hormone melatonin helps control your natural sleep-wake cycle. Natural levels of melatonin in the blood are highest at night. Some research suggests that melatonin supplements might be helpful in treating jet lag or reducing the time it takes to fall asleep - although the effect is typically mild. Melatonin might be more effective for other types of sleep issues, such as delayed sleep disorder or sleep disorders affecting circadian rhythm.

The most common melatonin side effects include:
  • Daytime sleepiness
  • Dizziness
  • Headaches
Other, less common melatonin side effects might include abdominal discomfort, mild anxiety, irritability, confusion and short-lasting feelings of depression.

In addition, melatonin supplements can interact with various medications, including:
  • Blood-thinning medications (anticoagulants)
  • Medications that suppress the immune system (immunosuppressants)
  • Diabetes medications
  • Birth control pills
If you're considering taking melatonin supplements, check with your doctor first - especially if you have any health conditions. The correct dose depends on the intended use. For example, circadian rhythm sleep disorders are often treated with 0.5 milligrams of melatonin a day, while doses of 3 to 5 milligrams a day might be used to treat jet lag or reduce the time it takes to fall asleep. In addition, remember that melatonin is generally recommended only for short-term use - up to two months. Some research indicates that longer term use might be appropriate in certain cases, however.

If you take melatonin, choose commercial supplements produced in a lab. Melatonin supplements made from animal sources might contain various contaminants. Don't engage in activities that require alertness - such as driving or operating heavy machinery - for four to five hours after taking melatonin.

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  4. Wade AG, et al. Prolonged release melatonin in the treatment of primary insomnia: Evaluation of the age cut-off for short- and long-term response. Current Medical Research and Opinion. 2011;27:87.
  5. Ferguson SA, et al. Melatonin agonists and insomnia. Expert Review of Neurotherapeutics. 2010;10:305.
  6. Morgenthaler TI, et al. Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. Sleep. 2007;30:1445.
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