Although melatonin is generally considered relatively nontoxic, it is worth noting that some marketed doses, such as 10 mg, can raise plasma concentrations to 60 times their normal values (20). There haven’t been any reports of people dying due to a melatonin overuse. But it can cause certain symptoms such as headaches, dizziness, stomach cramps, and depression if taken at a high dose. In such cases, it is better to discontinue and seek professional help.