melatonin (generic name)
- Auto Immune Conditions
- Bladder & Kidney Health
- Brain & Nervous System
- Care Transitions
- Dental Health
- Emotional Health
- Eye Health
- Falls Prevention
- Financial Planning
- General Safety
- Health Care Basics
- Healthy Living
- Hearing Loss
- Heart Health
- High Blood Pressure
- Life Transitions
- Lung Health
- Men's Health
- Nutrition & Weight Management
- Pain Management
- Preventive Health
- Sexual Health
- Stomach & Digestive Health
- Stress & Anxiety
- Women's Health
TraditionWARNING: DISCLAIMER: The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.
Adults (over 18 years old)
Studies have evaluated 0.5-50 milligrams of melatonin taken nightly by mouth. Research suggests that quick-release melatonin may be more effective than sustained-release formulations for sleep related conditions. Intramuscular injections of 20 milligrams of melatonin have also been studied.
In studies of patients with melanoma, melatonin preparations have been applied to the skin. Patients are advised to discuss cancer treatment plans with an oncologist and pharmacist before considering use of melatonin either alone or with other therapies.
Intranasal melatonin (1% solution in ethanol) at a dose of 2 milligrams daily for one week has also been studied for high blood pressure.
There are other uses with limited study and unclear effectiveness or safety. Use of melatonin for any condition should be discussed with a primary healthcare provider, appropriate specialist and pharmacist prior to starting and should not be substituted for more proven therapies.
Children (under 18 years old)
There is limited study of melatonin supplements in children, and safety is not established. Use of melatonin should be discussed with the child's physician and pharmacist prior to starting.
SafetyDISCLAIMER: Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.
There are rare reports of allergic skin reactions after taking melatonin by mouth. Melatonin has been linked to a case of autoimmune hepatitis.
Side Effects and Warnings
Based on available studies and clinical use, melatonin is generally regarded as safe in recommended doses for short-term use (three months or less). Available trials report that overall adverse effects are not significantly more common with melatonin than placebo. However, case reports raise concerns about risks of blood clotting abnormalities (particularly in patients taking warfarin), increased risk of seizure, and disorientation with overdose.
Commonly reported adverse effects include fatigue, dizziness, headache, irritability, and sleepiness, although these effects may occur due to jet lag and not to melatonin itself. Fatigue may particularly occur with morning use or high doses, and irregular sleep-wake cycles may occur. Disorientation, confusion, sleepwalking, vivid dreams, and nightmares have also been noted, with effects often resolving after cessation of melatonin. Due to risk of daytime sleepiness, those driving or operating heavy machinery should take caution. Melatonin may also cause infection. Ataxia (difficulties with walking and balance) may occur following overdose.
It has been suggested that melatonin may lower seizure threshold and increase the risk of seizure, particularly in children with severe neurologic disorders. However, multiple other studies actually report reduced incidence of seizure with regular melatonin use. This remains an area of controversy. Patients with seizure disorder taking melatonin should be monitored closely by a healthcare professional.
Mood changes have been reported, including giddiness and dysphoria (sadness). Psychotic symptoms have been reported, including hallucinations and paranoia, possibly due to overdose. Patients with underlying major depression or psychotic disorders taking melatonin should be monitored closely by a healthcare professional.
Melatonin should be avoided in patients using warfarin, and possibly in patients taking other blood-thinning medications or with clotting disorders.
Melatonin may cause drops in blood pressure. Caution is advised in patients taking medications that may also lower blood pressure. Based on preliminary evidence, increases in cholesterol levels may occur. Caution is therefore advised in patients with high cholesterol levels, atherosclerosis, or at risk for cardiovascular disease. Abnormal heart rhythms have been associated with melatonin.
Elevated blood sugar levels (hyperglycemia) have been reported in patients with type 1 diabetes (insulin-dependent diabetes), and low doses of melatonin have reduced glucose tolerance and insulin sensitivity. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.
Hormonal effects have been reported, including decreases or increases in levels of luteinizing hormone, progesterone, estradiol, thyroid hormone (T4 and T3), growth hormone, prolactin, cortisol, oxytocin, and vasopressin. Gynecomastia (increased breast size) has been reported in men, as well as decreased sperm count (both which resolved with cessation of melatonin). Decreased sperm motility has been reported in rats and humans.
Mild gastrointestinal distress commonly occurs, including nausea, vomiting, or cramping. Melatonin has been linked to a case of autoimmune hepatitis; it has also been linked to the triggering of Crohn's disease symptoms.
It has been theorized that high doses of melatonin may increase intraocular pressure and the risk of glaucoma, age-related maculopathy and myopia, or retinal damage. However, there is preliminary evidence that melatonin may actually decrease intraocular pressure in the eye, and it has been suggested as a possible therapy for glaucoma. Patients with glaucoma taking melatonin should be monitored by a healthcare professional.
Pregnancy and Breastfeeding
Melatonin supplementation should be avoided in women who are pregnant or attempting to become pregnant, based on possible hormonal effects. High levels of melatonin during pregnancy may increase the risk of developmental disorders. In animal studies, melatonin is detected in breast milk and therefore should be avoided during breastfeeding. In men, decreased sperm motility and decreased sperm count are reported with the use of melatonin.