Melatonin is a naturally occurring hormone produced primarily by the pineal gland in the brain. Its main function involves regulating the body’s sleep-wake cycle, also known as the circadian rhythm. As darkness increases, the pineal gland produces more melatonin, signaling to the body that it is time to prepare for sleep. Conversely, light exposure reduces melatonin production, promoting wakefulness. This hormone is widely available as an over-the-counter supplement, commonly used to assist with sleep difficulties like insomnia or to help adjust to new time zones.
Overdose Potential
While ingesting more melatonin than recommended is possible, it is not typically considered dangerous as many medications. Melatonin has a very high therapeutic index, meaning the dose required to cause significant harm is substantially greater than its intended effects. Unlike many prescription drugs, melatonin is not strictly regulated by the U.S. Food and Drug Administration (FDA), leading to inconsistencies in product labeling and actual content. Some supplements contain significantly more or less melatonin than advertised, or even unlisted ingredients. Despite these inconsistencies, severe toxicity from melatonin alone is uncommon.
Symptoms of Excessive Melatonin
Excessive melatonin can lead to side effects, generally mild and resolve once processed by the body. Common symptoms include increased drowsiness, dizziness, and headaches. Some might experience nausea, stomach pain, or gastrointestinal discomfort. Less common effects include irritability, short-lasting depression, or vivid dreams. These symptoms indicate that more melatonin was consumed than the body could effectively utilize, but they do not signify a life-threatening emergency.
Lethal Dose and Risk of Death
A fatal overdose from melatonin is exceedingly rare. Experts have not identified a specific lethal dose (LD50) for melatonin, which is the amount that would cause death in 50% of people. Even very high doses have not proven fatal in animal studies, as the body processes melatonin efficiently, preventing toxic accumulation. While poison control centers report increased calls regarding melatonin ingestions, particularly among children, serious outcomes like hospitalizations remain a small percentage. Two deaths in children under two years old were reported in the U.S. between 2012 and 2021 related to melatonin ingestion, though it is unclear if melatonin was the sole cause or if comorbidities were involved.
When to Seek Medical Attention
While a melatonin overdose is generally not life-threatening, medical attention is advised in certain situations. If an unusually large dose was ingested, or if severe or unexpected symptoms occur, contact a healthcare provider or poison control center. The U.S. Poison Control Center can be reached at (800) 222-1222. Immediate emergency medical attention (calling 9-1-1) is necessary for severe symptoms like difficulty breathing, seizures, or loss of consciousness. This is especially important for individuals with underlying health conditions or those taking interacting medications like blood thinners, immunosuppressants, or certain blood pressure medications, as these can increase risks.