Insomnia Home > Melatonin Side Effects

Daytime drowsiness, dizziness, and abdominal cramps are some of the side effects that may occur with melatonin. In most cases, side effects can be lessened by making adjustments in the dosage or by switching from a daytime to nighttime dosage. There are also a number of potentially serious side effects of melatonin that may require immediate medical attention, such as anxiety, low blood pressure, or seizures.

Does Melatonin Cause Side Effects?

As with any medication or supplement, side effects are possible with melatonin. Interestingly, melatonin is more likely to have bothersome side effects if you take it at the wrong time of the day (usually, it should be taken at night).
 
(This article covers many, but not all, of the possible side effects with melatonin. Your healthcare provider can discuss a more complete list of melatonin side effects with you.)
 

Possible Side Effects of Melatonin

Possible bothersome (although not usually serious) side effects of melatonin may include:
 
  • Daytime drowsiness
  • Dizziness
  • Headaches
  • Abdominal cramps (stomach cramps)
  • Irritability
  • Nausea and vomiting
  • Shakiness (tremor).
     
Often, these side effects can be lessened by simple adjustments in the melatonin dosage or in the timing of the dosage. For instance, taking melatonin in the morning is likely to interfere with the normal sleep-wake cycle, possibly leading to daytime drowsiness or perhaps even insomnia at night. Switching to an evening dose may reduce such side effects. Also, lowering the dose may help with many side effects.
 

Melatonin Side Effects to Report

Some side effects with melatonin, while occurring infrequently, are potentially serious and should be reported immediately to your healthcare provider. These include, but are not limited to:
 
  • Low blood pressure (known medically as hypotension)
  • Depression (or a worsening of depression symptoms)
  • Anxiety
  • Confusion
  • Seizures
  • Signs of an allergic reaction, such as a rash, hives, itching, swelling of the mouth or throat, wheezing, or difficulty breathing.
     
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
List of references (click here):
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