Referring to the OP's first post, I don't know what dosage a fistful of melatonin is.
So what's the correct dosage???
There's the MIT study that says that 0.3 mg/daily is enough and that any more is less effective in treating insomnia.
http://newsoffice.mit.edu/2001/melatonin-1017
There's also dosage levels from the Mayo Clinic for different medical conditions.
http://www.mayoclinic.org/drugs-supplements/melatonin/dosing/hrb-20059770
Summarized here in a table:
http://www.melatonin.com/melatonin-dosage.php
From the Mayo Clinic
"For circadian rhythm sleep disorders in people with and without vision problems, melatonin has been taken by mouth as a single dose of 0.5-5 milligrams before bed or as a daily dose for 1-3 months.
For delayed sleep phase syndrome, melatonin has been taken by mouth in doses of 0.3-6 milligrams, with five milligrams being most common, daily before sleeping for two weeks to three months."
I take 1 mg daily. My approach was to start with the lower level, 0.3 mg, and work my way up to a dosage that helps me sleep and doesn't give me any side effects.