What would happen if i overdosed on melatonin?

Nothing: You may get tired; don't drive a car or operate machinery. However, if you are thinking of harming yourself -- don't do it, and phone a crisis line now. Being a teenager is tough & there are folks ready to help. Of people who tried to take their lives & failed, 99% are glad one year later that they failed.

That depends on how : High the overdose was. A melatonin overdose could lead to symptoms like marked sedation, headache, nausea, vomiting, upset stomach, low blood pressure, dizziness, confusion, disorientation, tremor, liver problems, weakness & seizures. If you are having strong thoughts of self-harm, please have someone take you to the er or call 911 for transport.