This problem has been on my brain lately since I've been navigating some health issues of my own--I'm not diagnosed with anything, and I'm optimistic that my problem is a short-term problem, but for many people, chronic health problems get in the way of a typical workweek. I recently read that 45% of Americans have at least one chronic disease.
Some have frequent doctor appointments. Some have limits on the type of physical activity they can handle. Some can't drive. Some can work, but only for a limited number of hours or days before fatigue sets in.
This doesn't mean that they're less dedicated to their jobs or less capable of doing them. It might mean that an employer has to make some accommodations. Maybe a chair for an employee who might otherwise stand, or maybe more frequent but shorter breaks. I think employee wellness programs are a good idea. Most of all, I would hope employers would be willing to grant any employees with health problems all the flexibility they need.
Where do you think you might work if you could only work for three hours at a time? What if you couldn't drive? What if you could only work for short bursts at a time?
Chronic illness can cost employers a lot of money in terms of absenteeism, lost productivity, and more. But I also think that with so many people dealing with illness, employers are going to have chronically ill employees at some point, and it's smart to have plans in place to help those who need it.
Fortunately, there are resources to help you with work issues if you have a chronic illness as well as to help employers. Every situation is different, and only you and your doctor can determine how much you can handle and what your employer (or prospective employer) needs to know. Inform yourself about laws relating to illness and disabilities and employment, and make sure you understand your employer's policies as well (I thought this New York Times article had some great tips). Be open to alternatives, and don't impose limits on yourself before you know all your options.