Melatonin Side Effects

by on June 19, 2012


As a dietary supplement, melatonin has many medical benefits and there are very few side effects. The most frequently reported side effects of Melatonin include daytime drowsiness, headaches, and temporary depression. Patients who have been diagnosed with depression, high blood pressure, diabetes, or epilepsy may experience more serious side effects when they take melatonin.

Common Melatonin Side Effects

Individuals who take melatonin in low doses for no longer than 3 months at a time will usually not experience any major side effects. Adverse reactions to this supplement are more likely at higher dosages, typically 3 mg or more per day, and may increase with continued use. Common melatonin side effects include:

  • Headache
  • Dizziness
  • Abdominal pain
  • Irritability
  • Drowsiness, even the day after taking melatonin
  • Shaking

If any of these symptoms are severe or do not subside, stop taking melatonin and let your doctor know. Most people who take melatonin will experience sleepiness and a decreased level of alertness. Do not drive or operate machinery for at least four hours after taking this medication, even if you feel fine.

Serious Melatonin Side Effects

More serious side effects may occur in some individuals, especially those who do not take the supplement as directed or who use more than 3 mg of melatonin each day. Contact your doctor immediately if you experience any of these symptoms while taking melatonin:

  • Confusion
  • Unexplained mood changes
  • New or more severe signs of depression
  • Changes in behavior
  • Nightmares or unusual dreams
  • Changes in other hormone levels
  • Reduced blood flow
  • Hypothermia

Allergic reactions to melatonin are extremely rare, but can be dangerous. Get medical attention immediately if you experience:

  • Severe dizziness
  • Breathing difficulties
  • Swelling of the face, throat, or tongue
  • Skin rash
  • Itching

Side Effects in Children

According to studies, melatonin can successfully regulate the sleep-wake cycle of children and teens who suffer from central nervous system disorders like autism and mental retardation. The supplement can also help these children fall asleep faster, but the side effects of melatonin can pose greater risks to children.

Melatonin can affect the way other hormones behave within the body which may interfere with normal development, particularly in preteens and adolescents. Case studies have not presented a reason for serious concerns, but you should still discuss the possible side effects of melatonin with your child’s doctor before administering it.


The effects of increased levels of melatonin during pregnancy are not known but the supplement is not recommended for women who are pregnant or plan to become pregnant. There is a possibility that the drug could cause harm to an unborn baby. Melatonin is thought to interfere with normal ovulation and could make it difficult or impossible to become pregnant. Infants who breastfeed may also be at risk if their mothers take melatonin. Do not take this drug while breastfeeding.

Other Conditions

Individuals with certain medical conditions are at a higher risk of adverse side effects from melatonin and should discuss the use of the supplement with their doctor before taking it. Patients who suffer from depression may experience worsened symptoms when they take melatonin. The supplement can also increase the blood sugar level of diabetes patients and may cause an increase in blood pressure, especially when used with certain medications. Individuals with epilepsy, liver disease, or an immune system disorder should discuss the risks and benefits of taking melatonin with their doctor.

Other Medications

The side effects of melatonin may be intensified by some medications and substances. There are also drugs that increase melatonin levels and should not be used with a melatonin supplement. Other medications may become less effective when melatonin levels are elevated and could increase the risk of dangerous side effects. Talk to your doctor before using any of the substances below with melatonin supplements:

  • Sedatives and CNS depressants like Klonopin, Ambien, etc.
  • Oral contraceptives, including Triphasil, Ortho-Novum, etc.
  • Products with caffeine, such as coffee, tea, soft drinks, etc.
  • Fluvoxamine
  • Diabetes medications like Amaryl, insulin, Orinase, etc.
  • Immunosuppressants such as Zenapax, CellCept, Rapamune, etc.
  • Anticoagulants or blood thinners, including Naprosyn, warfarin, aspirin, ibuprofen, etc.
  • Procardia XL
  • Verapamil
  • Flumazenil
  • Herbal supplements that slow blood clotting, such as ginger, garlic, red clover, willow, etc.
  • Other supplements that may cause drowsiness, including California poppy, St. John’s wort, etc.

When used properly, melatonin supplements can provide an assortment of benefits to improve a variety of conditions. Most individuals will not experience any melatonin side effects. Those who do have reactions to the drug typically only have mild symptoms without any serious complications. If you are taking melatonin and experience any unusual side effects, either physical or mental, stop using the product and contact your doctor. Melatonin may cause side effects or drug interactions besides those mentioned here.