Up to 1000mg once per day now, but had to work up slowly over a couple of months, as I wasn't able to tolerate even 10mg at first. You need the "flushing" type of nicotinic acid (it causes your skin to go hot and red for about half an hour, but tolerance of this gradually increases), avoid the "slow release" or "non-flushing" forms of Nicotinic acid. For melatonin I started on 3mg and worked up to 9mg.