You’re absolutely right—many studies define 5 mg of melatonin as a “high dose.” However, people often take much larger amounts (in my view, anything above 20 mg) for reasons beyond sleep, such as potential anti-aging or anti-inflammatory effects.
Personally, I’ve found that my sleep response is essentially the same whether I take 1 mg or 1 gram of melatonin. The reason I initially began experimenting with high doses was based on a book I read in the 1990s, which proposed that melatonin could have anti-aging properties.
“The pharmacokinetic features of melatonin that make it antioxidative and anti-inflammatory suggest that melatonin may be considered for its therapeutic use as an anti-aging agent.”
“Melatonin can decrease mitochondrial dysfunction and cellular aging by modulating the sirtuin1 pathway, limiting the oxidation of cardiolipin, upregulating Nrf2, downregulating NF-κB, and suppressing proinflammatory markers such as NO, COX-2, NLRP3, and beta-amyloids.”
Most research involving doses higher than 5 mg focuses on safety, and the data so far shows a favorable profile. The most commonly reported side effects are daytime drowsiness and headaches.
Personally, I experience a mild headache upon waking if I take more than 1 gram, but I don’t feel any daytime drowsiness.
Examples from Research
Here are some papers and clinical studies on high-dose melatonin:
“Melatonin as an Anti-Aging Therapy for Age-Related Cardiovascular and Neurodegenerative Diseases”
“The use of high-dose melatonin in liver resection is safe: first clinical experience”
“Melatonin decreases inflammatory changes after major liver resection, thus positively influencing the postoperative course.”
In this study, 50 patients received a single preoperative dose of 50 mg/kg body weight. For someone like me (~70 kg), that would be about 3.5 grams.
“Safety of higher doses of melatonin in adults: A systematic review and meta-analysis”
“Overall, there has been limited adverse event reporting from high-dose melatonin studies. Based on this limited evidence, melatonin appears to have a good safety profile.”
"https://www.researchgate.net/publication/387476163_A_cross-sectional_report_on_the_use_of_high_doses_of_melatonin_in_humans
Here are two YouTube videos featuring individuals who use 1 gram or more of melatonin daily. The comment sections also contain a number of interesting user experiences:
“https://www.youtube.com/watch?v=a-d2B7CjjKw”
“https://www.youtube.com/watch?v=aTnq5fHi25s”
