Melatonin Side Effects and Interactions

Reviewed by Terri Forehand RN
Melatonin treats insomnia

The side effects of melatonin are rare, but they do occur in a small number of people taking this supplement. Although the Mayo Clinic reports that the supplement is generally considered safe, some have reported side effects.

Common Side Effects

According to data found on the Mayo Clinic's website, the percentage of people taking melatonin who report side effects is about equal to those taking a placebo. The most common side effects reported are vivid nightmares or dreams, dizziness, headaches, and nausea.

Nightmares and Dreams

The University of Maryland Medical Center (UMMC) lists nightmares and vivid dreams as a common side effect of melatonin supplementation. Similar side effects include more frequently remembered dreams and dreams paralysis.

While many people do not find these side effects troubling, those with a history of sleep disorders or psychiatric problems may find it difficult to cope with disturbing visions and dreams. Typical users reported dreams becoming more vivid after about ten days taking melatonin.

If nightmares and dreams become problematic, simply stop taking melatonin. This side effect vanishes in a few days.


The UMMC also reports that many individuals who take melatonin supplements feel light-headed when standing up quickly. Sudden shifts in position may cause drops in blood pressure in certain individuals. Melatonin appears to magnify this effect, causing increased dizziness. If you experience frequent bouts of dizziness, seek medical attention and discontinue melatonin.


WebMD reports headaches to be a side effect of melatonin supplementation. Most reporting this side effect note that it is a different sort of headache than what they've experienced in the past, characterized by a dull ache above the eyes and felt deep within the brain. Discontinuing melatonin removes this side effect.


According to Dr. Oz, melatonin can cause nausea. This may be particularly true if you take too high of a dose.

Allergic Reactions

The melatonin package insert reports a handful of people reported allergic reactions to melatonin supplements. Although melatonin naturally occurs in the body, the higher concentrations of melatonin, or other ingredients in the supplements, may create conditions leading to an allergic response. Any sign of rash, swelling of the throat, tongue or lips, or tightness in the chest may indicate an allergic reaction to the supplement. Seek medical help immediately if you think you are having an allergic reaction to melatonin or any supplement.

Psychiatric Symptoms

The rarest of the side effects of taking melatonin includes psychiatric disorders. According to Web MD, these side effects are rare and typically not severe. One should be aware of them in case they occur. While taking melatonin, if you feel confused, disoriented, or have trouble gathering your thoughts, discontinue the product. Some have also reported sudden, uncontrollable outbursts of anger. Again, discontinue melatonin and side effects should dissipate.

Melatonin Cautions and Contraindications

Some people should not take melatonin.

  • People with autoimmune disease should not take melatonin. Some studies show that melatonin supplementation may exacerbate autoimmune conditions.
  • Pregnant women or those trying to become pregnant should avoid taking melatonin. Melatonin is a hormone, and the UMMC reports taking melatonin supplements may affect fertility.

Possible Interactions

Melatonin interacts with several herbs and medications, according to the NIH. These drugs include:

  • Blood thinners
  • Antidepressants
  • Hormonal contraceptives
  • Central nervous system depressants
  • Fluvoxamine (a drug for obsessive compulsive disorder)
  • Sedatives
  • Anticoagulant and antiplatelet drugs
  • Beta blockers
  • Non-steroidal anti-inflammatory drugs
  • Steroids
  • Immunosuppressants
  • Herbs that thin blood including garlic, ginseng, willow, clove, and red clover
  • Use caution with herbs that promote sleepiness such as kava kava, valerian, and hops
  • If you drink a lot of coffee or other beverages containing caffeine, decrease your consumption while taking melatonin. Caffeine may cancel out the positive benefits of melatonin supplements.

Talk to Your Doctor

While melatonin can be a safe and effective way to treat insomnia, it is still a hormonal supplement. Be sure you talk to your doctor before you begin taking melatonin and report any medications, vitamins, or herbal supplements you are taking to avoid complications and side effects.

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