After several nights of losing sleep, even a loss of just 1-2 hours per night, your ability to function suffers as if you haven't slept at all for a day or two. People who are sleep deficient take longer to finish tasks, have a slower reaction time, and make more mistakes.
Some people nap as a way to deal with sleepiness. Naps may provide a short-term boost in alertness and performance. However, napping doesn't provide all of the other benefits of night-time sleep. Thus, you can't really make up for lost sleep.
Some people sleep more on their days off or go to bed later and get up later. Sleeping more on days off might be a sign that you aren't getting enough sleep. Although extra sleep on days off might help you feel better, it can upset your body's sleep–wake rhythm.
Bad sleep habits and long-term sleep loss will affect your health. If you're worried about whether you're getting enough sleep, try using a sleep diary for a couple of weeks. Write down how much you sleep each night, how alert and rested you feel in the morning, and how sleepy you feel during the day. Show the results to your doctor and talk about how you can improve your sleep.