More threads by David Baxter PhD

David Baxter PhD

Late Founder
Melatonin side effects: What are the risks?
By Mayo Clinic Staff
Oct 18, 2007

I'm considering taking melatonin to help me sleep. What do I need to know about melatonin side effects? ~ No name / No state given

The hormone melatonin helps control your natural sleep-wake cycle. In fact, natural levels of melatonin in the blood are highest just before bedtime. If you're struggling with insomnia, melatonin supplements may help you fall asleep or stay asleep. However, there are no guarantees. Most studies show melatonin to be only minimally effective for insomnia. Melatonin may play a stronger role in fighting jet lag. Melatonin side effects may include daytime sleepiness, dizziness, headaches and abdominal discomfort. Confusion, sleepwalking or nightmares also are possible. Some studies suggest that melatonin increases the risk of seizures, but others disagree. Melatonin may interact with various medications. The optimal dose of melatonin isn't certain, and the long-term effects are unknown. Talk to your doctor before taking melatonin, especially if you have any underlying health conditions. If you decide to take melatonin, make sure the supplements are manufactured in a lab, not derived from animals.


I never gave much thought to the use of melatonin, expecting it to be fairly benign. If Forum members have had experience, whether favorable or disappointing, it would be interesting to hear your comments on the effectiveness of melatonin from your own experience

However David's posting, David raises a few red flags, particularly in connection with possible drug interactions, which I would like to address:


USES: Melatonin has been used for sleep disorders (e.g., insomnia and jet lag). Some herbal/diet supplement products have been found to contain possibly harmful impurities/additives. Check with your pharmacist for more details regarding the particular brand you use. The FDA has not reviewed this product for safety or effectiveness. Consult your doctor or pharmacist for more details.

HOW TO USE: Take this product by mouth generally 2 hours before bedtime. Results may be seen within 30 minutes. Follow all directions on the product package. If you are uncertain about any of the information, consult your doctor or pharmacist. Full benefit is usually seen after 1 to 3 days of use. If your condition persists or worsens or if you think you may have a serious medical problem, seek immediate medical attention.

SIDE EFFECTS: Headache or altered sleep pattern may occur. If either of these effects persists or worsens, contact your doctor promptly. Unlikely but report promptly: mental or mood changes, itching, fast heartbeat, sensation of heaviness in the head. If you notice other effects not listed above, contact your doctor or pharmacist.

PRECAUTIONS: If you have any of the following health problems, consult your doctor before using melatonin:

disorders of immune system, liver or kidney disease, stroke, depression, epilepsy, diabetes. Limit alcohol intake, as it may aggravate certain side effects of this product.

  • Caution is advised when performing tasks requiring alertness (e.g., driving). Liquid preparations of this product may contain sugar and/or alcohol.
  • Caution is advised if you have diabetes, alcohol dependence or liver disease. Ask your doctor or pharmacist about the safe use of this product. Melatonin is not recommended for use in children (under 20 years old). Do not use this product if you plan to become pregnant.
  • It may have a contraceptive (birth control) effect. Melatonin is not recommended for use during pregnancy.
  • Consult your doctor before using this product.
  • It is not known if this product is excreted into breast milk. Because of the potential risk to the infant, breast-feeding while using this product is not recommended. Consult your doctor before breast-feeding.

Melatonin Drug Interactions:

Before using this product, tell your doctor or pharmacist of all prescription and nonprescription medications you may use, especially of:

  • immunosuppressants (e.g., azathioprine, cyclosporine), corticosteroids (e.g., prednisone).
  • Also report use of drugs that cause drowsiness such as: sleeping pills, anti-anxiety drugs, narcotic pain relievers (e.g., codeine), sedatives, psychiatric medicines, anti-seizure drugs, muscle relaxants, antihistamines that cause drowsiness (e.g., diphenhydramine), herbs that cause drowsiness (e.g., valerian, kava).
  • Check all nonprescription medicine labels carefully, especially cough-and-cold preparations since many contain drowsiness-causing antihistamines (e.g., diphenhydramine).
  • Consult your pharmacist if you are uncertain.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly.

NOTES: If you are having surgery, notify your doctors you are taking this herbal product.


Another resource for information on drug interactions with melationin:
University of Maryland Medical Center
I haven't heard of too many side effects, or ones that are too severe for that matter either. I have heard that melatonin shouldn't be taken regularly by young people (under 35), unless recommended by a doctor since the body normally produces enough melatonin and taking a supplement regularly could cause an overdose. But I know as a person ages, melatonin levels decrease, so it can be helpful for the elderly who have difficulty sleeping. I think for those people, it's a good alternative to a prescription.
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I've taken Melatonin, occasionally, i've found it helps a bit fro one night but i've that subsequent nights it doesn't seem to work at all.
I took it to help me stop Klonopin. About 2 weeks ago I stopped taking Melatonin (stopped Klonopin in June) and I actually sleep better now and I am not as groggy during the day.
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