I take epilim chrono 500mg which isn't actually equal depakote er. (500mg epilim = 333mg sodium valproate + 145 mg valproic acid),so when to test?

Random: The idea is this medication is supposed to generate a steady state level after about 3 days. Peak and trough levels matter if you are looking for toxicity or sub-therapeutic levels with medications with a short half life. Also Depakote has a very wide therapeutic level (50-100) Consider obtaining a Vit D level (which is often low) and checking ammonia after being on this medication a while.

3 days: Half life of valproate sodium and valproic acid is 16 hours. Steady state is reached at 3 1/2 half lives--i.e. 62 hours. For ease of calculation, 72 hours would show a steady state. Measure trough level--i.e. just before your next dose schedule.