Is there any evidence regarding melatonin toxicity, tolerance, and addiction?

Overall, melatonin supplementation is relatively safe. First, melatonin toxicity is very low. Studies testing up to 240 mg^[1] and 500 mg^[2] taken orally do not report any toxic effects. Second, tolerance does not seem to be an issue. A study examining the continued administration of melatonin over 6–12 months did not find any evidence of tolerance.^[3] Third, there is currently no evidence to support addiction or withdrawal symptoms. However, doses higher than 2 mg have not been sufficiently studied over the long term. Lastly, if you’re worried about the potential testosterone-lowering effect of melatonin, rest assured, there is currently no conclusive evidence to support this claim.