Common Side Effects of Melatonin
Melatonin, often used for sleep issues, commonly causes daytime drowsiness, dizziness, headaches, and nausea. These effects occur in 1-10% of users, especially at higher doses like 3-10 mg, and typically resolve within hours as the hormone clears the body.[1][2]
Less Common or Serious Side Effects
Rarer reactions include vivid dreams or nightmares, stomach cramps, irritability, reduced alertness, and temporary depressive feelings. High doses (over 10 mg) may disrupt natural hormone cycles, potentially affecting blood pressure or glucose levels. Allergic responses like rash or swelling are possible but infrequent.[1][3]
Side Effects in Specific Groups
Children may experience bedwetting, agitation, or morning grogginess. Pregnant or breastfeeding individuals should avoid it due to unknown risks to fetal development. Older adults report higher rates of confusion or falls from impaired coordination.[2][4]
What Causes These Side Effects?
Melatonin mimics the body's sleep hormone, but supplements often exceed natural levels (0.1-0.3 mg nightly), leading to carryover effects into daytime. Interactions with blood thinners, diabetes meds, or immunosuppressants amplify risks like bleeding or low blood sugar.[1][3]
How Long Do Side Effects Last?
Most fade within 4-8 hours, matching melatonin's half-life. Chronic use might lead to tolerance, worsening sleep over time. Stopping abruptly rarely causes withdrawal, but gradual tapering helps if dependent.[2]
Drug Interactions and Risks
Avoid combining with alcohol, sedatives, or antidepressants, as this intensifies drowsiness or serotonin syndrome risk. It may reduce birth control effectiveness or interfere with seizure meds.[3][4]
When to See a Doctor
Seek help for severe symptoms like chest pain, rapid heartbeat, confusion, or mood changes persisting over 24 hours. Overdose (e.g., 30+ mg) can cause hypothermia or hypertension—call poison control.[1]
[1]: Mayo Clinic, "Melatonin side effects." https://www.mayoclinic.org/drugs-supplements-melatonin/art-20363071
[2]: NIH Office of Dietary Supplements, "Melatonin Fact Sheet." https://ods.od.nih.gov/factsheets/Melatonin-HealthProfessional/
[3]: WebMD, "Melatonin: Uses, Side Effects, Interactions." https://www.webmd.com/vitamins/ai/ingredientmono-940/melatonin
[4]: Drugs.com, "Melatonin Side Effects." https://www.drugs.com/sfx/melatonin-side-effects.html