What is the best time during the day to take folic acid ? i feel insomnia at night after taking it

Never heard of that: But that's ok...if you say that folic acid is the cause for your insomnia...perhaps, there is something else of a chemical nature present in the tablet that is offending your system. You could try a different brand of that VITAMIN/NUTRITIONAL SUPPLEMENT which is over the counter to see if symptoms improve. Or you could simply dose the tablet when you awaken and see if that helps getting to bed.