When the condition prevents you from performing your duties as normal?

I don't go in if I feel like I will spend most of the day being unproductive or the condition is infectious enough to contaminate other people.

This is for an important process going on.

I don't understand what you mean by this.

When you show up for the interview wearing only clown makeup and chaps and answer every question by sliding the business end of a razor blade across your palm and you can hear your potential boss screaming "you'll never work in this town" behind you as the police lead you away. I'll never make that mistake again.

I'll take a genuine crack at this.

I know I am too sick to work when I am unable to mentally function properly. My job primarily requires me to use my brain; I have no office to frequent nor co-workers I have to interact with. It's just me and my 'puter most days. I know I am too sick to work if I frequently misspell words, or if I read back over a sentence and realize it makes no sense. Lucky for me, a nap will temporarily resolve the issue, or a few days away from the computer, if the illness is more serious.
I have never been so sick longterm that work has been an impossibility. I wish you well, btgog.

Sorry to be unclear about the process, what I mean is that I'm asking this question for a purpose as part of work I am doing that I can't talk about. Your answers are really helpful so far, thanks!

The EEOC Enforcement Guidance on the Americans with Disabilities Act and Psychiatric Disabilities has some good info about reasonable accommodations and what would constitute a disability requiring them.

The Social Security criteria for "How Do We Decide If You Are Disabled?" might also help.

When my coworkers tell me that I look like I need to go home then I'll usually go home.

This also used to be my method when I'd show up to work hungover - or still messed up from the night before.

If I'm potentially infectious, I stay home. (In an office of 4, it's really important because if one of us gets sick--all of us get sick.)

If I'm thinking about death before I finish making breakfast--it's time for a mental health day. (Which is where I am now because I was starting to get burnt at work, whee!)

Lucky for me, my mental ailments tend to manifest as physical ailments as well. So physically, I stay home if I am coughing/sniffling excessively (disease vectors), have a fever, or a seriously upset stomach. The last one is usually a mental thing.

If we're talking long-term disability, then that's definitely something to discuss with a doctor. For my father, it was pretty clear that sleeping 18+ hours a day was not conducive to going to work, but when the fatigue abated a little bit and just left a mental fog, it was harder to convince both him and his employer that going in to his (mentally taxing) job was just not productive in the long run.

What is this not working you speak of? If I want to eat, I need to work. Functioning well or not. I do take a day or two here and there when I need it, though. And I'm lucky to have a job where I get summers off to reboot, plus a few weeks off at holidays during the year. So I'm never more than a month or two from some time off. Work has its own momentum, I find. You just keep going, whether you want to or not, and you get used to it, even thrive in it sometimes. I've worked through very serious depressions where I wasn't eating or sleeping much for weeks, and I find just the daily interaction with people helps pull me out of myself, even if I'm crying in the bathroom between classes.

If it's a physical issue, though, sometimes you just can't. Jon had his broken foot and there was no way he could work since his job requires him to be on his feet. Of course, if it turned into a permanent disability where he could never be on his feet that much, I imagine he would have found a job where he could sit. Sometimes it might be a matter of retraining or a different kind of job if the person has physical limitations.

Generally, for mental health issues, once a person's stabilized, I think it's good to work in some capacity, even if it's part-time. Work gives us structure and a sense of purpose. Too much time alone can exasperate mental health problems, I think. But there may be limits to how much stress a person can cope with, depending on their condition. Sometimes people will tend to do the least amount required of them, though. So it's tricky. I guess it's a case-by-case thing.

I've never taken a mental health day.

However, if I'm sick with something contagious, I stay home as soon as I'm sick and wait until I'm well to return to work.

If it isn't contagious, it all depends on how tired it makes me. If I'm gonna fall asleep at my machine, I go (or stay) home.

And when I stay home sick, I pretty much sleep the whole time.

Of course, this describes me when I had a job, so who knows? Maybe things have changed since then.

I can no longer afford to take time off, for either physical or mental illness. My company used to allow us to take a vacation or personal day (we don't get sick days. We do get 4 and 1/2 personal days a year). But someone in my store abused the priviledge, and now no one can get paid for taking a day off for illness. So unfortunately, I have to really be in horrible condition not to go in.