My son's largest dose is in the am. Although, previously we tried biggest in the pm. About 4 months ago I posted a question on this because it seemed that some gave biggest dose in pm, others in the am. The responses indicated it was about a 50/50 split. Apparently there is an early morning surge in hormone production. Some dr.s believe a large pm dose is the best way to supress the surge, others feel a large am dose. An adult once posted she noticed it more difficult to sleep with a large pm dose. Honestly, I haven't noticed a difference in my son's sleep since we switched to the largest dose in am. it is also too soon to tell if this affects his levels at all.