At what point does sleep deprivation become a problem?

I think sleep deprivation becomes a problem when it is already affecting your work/school and most especially your health.

The point where it disrupts your day to day activities. When you can no longer function well in going about your daily activities then that's when it is already a problem.

I think at the point where it's interfering with your normal functioning. If you're noticing that you can't or don't want to do the things you normally do, this may be due to tiredness. Sometimes it is even as subtle as mood changes. Sleep is an important part of how we function as human beings, so if something is causing problems with your sleep it's important to take steps to address it.

When you're getting less than 4 hours of sleep, or when you wake up tired. Your mind tries to cope with all of the loss of sleep, that if you keep getting, say 3 hours of sleep each night. Your mind is lacking the time to reproduce cells and get the rest from the long day.

At the point that you feel like sleeping but the problems of your life seem lot and you are unable relax properly.

It becomes a problem when you start having problem when concentrating, you start feeling tired the whole day, etc.

Sleep deprivation becomes a problem when you are doing anything at all, and can not seem to respond to this activity as you do the norm. Sleep deprivation becomes a problem when you cannot think straight, cannot move, cannot see the obvious (what might be right before your eyes!). It is to be taken seriously, my friend. It is literally affecting the way your brain acts and responds, like the way nicotine does to a smoker. Your cognitive abilities can be altered entirely, you can gain or lose weight rapidly. No doubt it is a large negative factor on your overall heath. I know that I struggled with remembering things, was far too easily irritable, and my mood swings came and went faster than a sparrow when I experienced a period of insomnia that disallowed regular sleeping patterns. I felt like my head was too heavy, that my feet weighed more with every step. I often struggled very much in school and was unable to grasp new concepts and notions insinuated and taught by my teachers. Wikipedia relates, "...attentional lapses also extend into more critical domains in which the consequences can be life-or-death; car crashes and industrial disasters can result from inattentiveness attributable to sleep deprivation." Your sleep is detrimental to your health; they are directly correlated. It is a massive issue with so many people. Keep yourself safe out there, friend. Get your sleep. Best wishes to you, dear.

When it impacts your job, school, family and people around you. That’s when sleep deprivation becomes a problem.

When your attention span suffers and you make simple mental mistakes such as forgetting simple things. Also, physically you may have a headache or feel "foggy".

It becomes a problem when you struggle to function properly, e.g. you feel week, unmotivated and tired.