What is the difference between qid and q6h?

Q 6 hours means that you take the medication around the clock every 6 hours, even during sleeping hours. An example would be 0900, 1500, 2100, 0300, 0900.

QID means 4 times a day, but the doses are divided during waking hours. An example might be 0900, 1300, 1700, 2100.