Can melatonin be taken in excessive amounts (overdose)?

Can You Take Too Much Melatonin?

Yes, you can take too much melatonin, and higher doses (≥10 mg) frequently cause more adverse effects without improving efficacy—in fact, doses above 5 mg may reduce effectiveness through receptor desensitization. 1

The Paradox of Melatonin Dosing

Lower doses are often more effective than higher doses. Melatonin works by binding to M1 and M2 receptors to regulate circadian rhythms and sleep architecture. 1 When you take doses of 10 mg or higher, you risk saturating these receptors or causing desensitization, which actually disrupts the normal circadian signaling mechanism rather than enhancing it. 1

The American Academy of Sleep Medicine explicitly recommends:

• Start with 3 mg of immediate-release melatonin taken 1.5-2 hours before desired bedtime 1, 2, 3
• Titrate in 3 mg increments only if needed after 1-2 weeks of ineffectiveness 1, 3
• Maximum dose should not exceed 15 mg 1
• Typical effective range is 3-5 mg for most adults 3

Adverse Effects Increase with Higher Doses

The most common side effects documented in clinical trials include:

• Daytime sleepiness/somnolence: 1.66% (most frequent adverse effect, particularly at higher doses) 1, 4
• Headache: 0.74% 1, 4
• Dizziness: 0.74% 4
• Morning grogginess and "hangover" effects are more commonly reported with higher doses due to melatonin's half-life extending into morning hours 1
• Gastrointestinal upset occurs more frequently at higher doses 1

A systematic review of high-dose melatonin (≥10 mg) found that while serious adverse events were rare, melatonin did significantly increase the risk of adverse events like drowsiness, headache, and dizziness (Rate Ratio = 1.40, p < .001) compared to placebo. 5

Duration Limits and Safety Concerns

The American Academy of Sleep Medicine recommends against long-term use of melatonin for chronic insomnia beyond 3-4 months due to insufficient safety data. 1, 3 Most clinical trial data supports use for 4 weeks or less. 1

Critical Safety Warnings:

• Use with extreme caution in patients taking warfarin—documented case reports show potential interactions 1, 3, 6
• Exercise caution in patients with epilepsy based on case reports 1, 3, 7
• Monitor for impaired glucose tolerance, particularly in patients with diabetes risk factors 1, 3
• Avoid in older adults with dementia for irregular sleep-wake rhythm disorder—the American Academy of Sleep Medicine recommends against this due to lack of benefit and potential harm, including detrimental effects on mood and daytime functioning 1

Product Quality Is a Major Concern

Melatonin is regulated as a dietary supplement in the U.S., not as a medication, raising significant concerns about purity and reliability of stated doses. 1, 3 This means the actual melatonin content can vary dramatically from what's on the label.

Always choose United States Pharmacopeial Convention (USP) Verified formulations to ensure you're getting the dose stated on the label. 1, 3

Drug Interactions to Avoid

• Fluvoxamine markedly increases melatonin levels because it inhibits CYP1A2, the primary pathway for melatonin metabolism—this creates a high risk of excessive melatonin effects 1
• CNS depressants and alcohol produce additive sedation and impair psychomotor performance when combined with melatonin 1
• Avoid taking melatonin in the morning or afternoon (except for specific circadian rhythm disorders) as this worsens circadian misalignment 1, 3

What Constitutes "Too Much"?

Based on the evidence:

• Doses above 5 mg appear no more effective than 5 mg and increase side effects 6
• Doses of 10 mg or higher cause receptor desensitization that may reduce effectiveness 1
• The therapeutic window is narrow: 3-5 mg is optimal for most adults 3

While melatonin has a favorable overall safety profile with no documented deaths even at supraphysiological doses 7, and systematic reviews show it is generally well-tolerated 5, 4, taking more than necessary provides no additional benefit and increases your risk of adverse effects, particularly morning sedation, headache, and gastrointestinal symptoms. 1, 5