Side effects of too much melatonin
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Side Effects of Excessive Melatonin Use
Common Side Effects of Melatonin Overdose
Melatonin, a hormone commonly used to treat sleep disorders, is generally considered safe. However, excessive intake can lead to several adverse effects. The most frequently reported side effects include drowsiness, dizziness, fatigue, headache, confusion, nightmares, hypotension, tachycardia, and hypothermia 15. These symptoms are typically mild and resolve on their own or with the cessation of melatonin use 15.
Daytime Sleepiness and Cognitive Impairment
One of the most common side effects of melatonin, even at therapeutic doses, is daytime sleepiness 12. This can impair cognitive functions and daily activities, making it a significant concern for users who need to remain alert during the day. Studies have shown that higher doses of melatonin can exacerbate these effects, leading to increased drowsiness and dizziness 2.
Headaches and Dizziness
Headaches and dizziness are also commonly reported side effects of melatonin use. These symptoms are generally mild but can be bothersome for some users 12. The incidence of these side effects appears to increase with higher doses of melatonin 2.
Mood Swings and Agitation
Some users may experience mood swings, agitation, and other mood-related side effects. These are less common but have been reported in various studies 1. The exact mechanism behind these mood changes is not well understood, but it is believed to be related to melatonin's interaction with the central nervous system.
Cardiovascular Effects
Melatonin can also affect cardiovascular function. Some studies have reported changes in blood pressure and heart rate, particularly in individuals taking high doses or those with pre-existing cardiovascular conditions 3. These effects are generally mild but warrant caution, especially in at-risk populations.
Endocrine and Metabolic Effects
Melatonin has been shown to influence endocrine functions, including reproductive parameters and glucose metabolism. Some studies have noted changes in blood sugar levels and insulin sensitivity, which could be particularly concerning for individuals with diabetes or other metabolic disorders 310. Additionally, melatonin has been used to mitigate metabolic side effects in patients undergoing treatment with antipsychotic medications like olanzapine 6.
Serious Adverse Events
While most side effects of melatonin are mild, there have been rare reports of more serious adverse events. These include severe agitation, mood swings, and even attempted suicide in extreme cases of overdose 15. However, such events are exceedingly rare and usually associated with very high doses of melatonin.
Conclusion
In summary, while melatonin is generally safe and well-tolerated, excessive use can lead to a range of side effects, including daytime sleepiness, headaches, dizziness, mood swings, and cardiovascular changes. Most of these side effects are mild and resolve on their own, but caution is advised, especially for individuals with pre-existing conditions or those taking high doses. Further research is needed to fully understand the long-term safety profile of melatonin, particularly in at-risk populations.
Sources and full results
Most relevant research papers on this topic
Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review
Melatonin treatment for sleep disorders is generally safe and well-tolerated, with few serious adverse events reported.
Systematic Review
Rigorous Journal
Highly CitedSafety of higher doses of melatonin in adults: A systematic review and meta‐analysis
Higher doses of melatonin in adults appear to have a good safety profile, but may increase the risk of drowsiness, headache, and dizziness.
Meta-AnalysisHighly CitedAdverse events associated with oral administration of melatonin: A critical systematic review of clinical evidence.
Oral melatonin supplementation has a generally favorable safety profile, with minor, short-lived adverse events affecting fatigue, mood, and psychomotor and neurocognitive performance.
Systematic ReviewHighly CitedClinical impact of melatonin on breast cancer patients undergoing chemotherapy; effects on cognition, sleep and depressive symptoms: A randomized, double-blind, placebo-controlled trial
Melatonin may counteract the adverse effects of adjuvant chemotherapy on cognitive function, sleep quality, and depressive symptoms in breast cancer patients.
RCTRigorous JournalHighly CitedAttempted suicide by Melatonin overdose: Case report and literature review
Melatonin overdose can cause drowsiness, dizziness, fatigue, headache, confusion, nightmares, hypotension, tachycardia, and hypothermia, requiring supportive measures and control of vital signs for early discharge.
Case ReportRigorous JournalMelatonin for prevention of metabolic side-effects of olanzapine in patients with first-episode schizophrenia: randomized double-blind placebo-controlled study.
Melatonin treatment short-term (3 mg/day) can reduce weight gain, abdominal obesity, and hypertriglyceridemia in patients with first-episode schizophrenia, potentially benefiting psychosis treatment.
RCTHighly CitedA single blind, placebo controlled, across groups dose escalation study of the safety, tolerability, pharmacokinetics and pharmacodynamics of the melatonin analog beta-methyl-6-chloromelatonin.
Beta-methyl-6-chloromelatonin is a safe and well-tolerated melatonin agonist at doses up to 100 mg, without causing side effects like hypothermia, bradycardia, or hypotension.
RCTPharmacokinetics of high‐dose intravenous melatonin in humans
High-dose intravenous melatonin does not induce sedation and no adverse effects were reported in this study.
RCTRigorous JournalThe effect of melatonin on normal sleep.
Low doses of melatonin do not affect sleep onset, duration, mood, or alertness, but may increase REM latency.
RCTHighly CitedThe Effects of Melatonin Supplementation on Parameters of Mental Health, Glycemic Control, Markers of Cardiometabolic Risk, and Oxidative Stress in Diabetic Hemodialysis Patients: A Randomized, Double-Blind, Placebo-Controlled Trial.
Melatonin supplementation for 12 weeks improves mental health, glycemic control, inflammatory markers, and oxidative stress in diabetic hemodialysis patients.
RCT