Can the night time use of melatonin lead to daytime fatigue? i take it at 7:30pm, go to bed at 9pm and wake at 5am.

Maybe in some people: Some people who used melatonin have complained of daytime sleepiness as a side effect, among some other mild side effects. However, people use melatonin to treat sleep problems and jet lag, which means these people are already having daytime sleepiness or daytime fatigue problems. That makes it hard to figure out. One can try changing the dose and/or the timing of the dose to see what happens.