Sleep Deprivation 😴

Is sleep deprivation something people can adjust to?
I am in my final year of Law School and for any of you who have experienced this, you know how little sleep us wanna-be lawyers get. Lately, I have been getting less sleep than ever (4-5 hours a night, usually). 
Is this something I can adjust to?? If so, how long does it take?? I can't afford to sleep more because then I risk my grades, but then again, I feel so terrible. The exhaustion hasn't affected my work... yet?