What are the effects of taking 20mg of Melatonin (N-acetyl-5-methoxytryptamine)?

From the Guidelines

I strongly advise against taking 20mg of melatonin due to the potential for increased side effects and lack of evidence supporting its efficacy at high doses. The typical recommended dose of melatonin for sleep issues in adults ranges from 0.5mg to 5mg, taken 30-60 minutes before bedtime, as supported by a clinical practice guideline for the pharmacologic treatment of chronic insomnia in adults 1. Starting with a lower dose (0.5-1mg) is generally advised, with gradual increases if needed. Melatonin is a hormone naturally produced by the pineal gland that helps regulate sleep-wake cycles. Supplemental melatonin can be helpful for certain sleep disorders, jet lag, or shift work adjustments, but higher doses don't necessarily work better and may cause side effects like headaches, dizziness, nausea, or daytime drowsiness.

Some key points to consider when using melatonin include:

• The American Academy of Sleep Medicine clinical practice guideline recommends melatonin at a dose of 2mg for treating sleep onset or sleep maintenance insomnia, with a mean reduction in sleep latency of 9 minutes compared to placebo 1.
• Long-term use of high doses of melatonin hasn't been well-studied, and potential harms may include new cognitive or behavioral abnormalities, complex behaviors like sleep driving, and exacerbation of depression and suicidal ideation in primarily depressed patients, as warned by the FDA labeling information for the melatonin receptor agonist ramelteon 2.
• If you're experiencing significant sleep problems that you feel require such a high dose, it would be better to consult with a healthcare provider who can evaluate your specific situation and recommend appropriate treatment options, which might include lower doses of melatonin or alternative approaches to improving sleep.

From the Research

Melatonin 20mg Dosage

• The effective melatonin doses varied according to each age group, with no mention of a 20mg dosage in the studies 3.
• Most studies evaluated the use of melatonin at doses ranging from 0.5 to 6 mg, depending on the age group 3, 4.
• One study investigated the safety of higher doses of melatonin (≥10 mg) in adults, but did not specifically examine a 20mg dosage 5.

Safety and Efficacy of Melatonin

• Melatonin has been shown to be well-tolerated and have no obvious short- or long-term adverse effects 4.
• The use of melatonin did not demonstrate toxicity or severe side effects, nor dependence, even when administered at high doses 3.
• A meta-analysis found that melatonin can reduce sleep onset latency in primary insomnia, delayed sleep phase syndrome, and regulate sleep-wake patterns in blind patients 6.
• Another study found that melatonin can advance the time of sleep onset, but the effect is modest and variable 7.

High-Dose Melatonin

• A systematic review and meta-analysis found that high-dose melatonin (≥10 mg) appears to have a good safety profile, but better safety reporting in future long-term trials is needed to confirm this 5.
• The study found that melatonin did not cause a detectable increase in serious adverse events or withdrawals due to adverse events, but did appear to increase the risk of adverse events such as drowsiness, headache, and dizziness 5.