How much sleep can you lose without throwing off your circadian rhythm?

Sleep and circadian: Circadian rhythm is about light/dark timing and the 24 cycle that human beings use to entrain this system. If sleep restriction is thrown in to compound this issue, can create some issues. In general somewhere as little as 4 hours and as much as 12 hours can throw off our usual cycle depending on when this change occurs. For example waking up 3am (usually dark) and then expecting bedtime 11pm.

irrelevant: Sleep loss and circadian rhythm are unrelated in some ways. If you loose sleep you loose sleep and this will not affect the rhythm . If you affect the rhythm by phase shift usually you loose sleep as well.