I am Uk based and not sure whether you have the same legal protection in the USA. Here we have law which means that an employer cannot discriminate against someone with a long term health problem - although as you say sometimes employers may look for loop holes, although in my experience this is more likely to happen in smaller businesses, the larger ones have more to lose if they are caught out.

Saying that the employer does not need to know someone's actual diagnosis to be obliged to make adjustments for them, they just need to know that the person has a long term health problem, how it may impact on work and what control measures they may have to put in place.

Obvioulsy if an employer does not know that someone has a health problem then they would not be expected to make any allowances for them. So I would not say that you should never tell your employer about your health especially if the extra demands they may be putting on you may make your symptoms worse. Nor am I saying you should always tell your employer - you may be best placed to know how they may react. I would just think carefully about the pros and cons, bearing in mind that if your health problem is made worse by work then it may even lead to you needing sick leave, when in fact this could be avoided if your employer knew you had health issues and was prepared to acknowledge them and support you.

It is a hard decision I know.....I have not told my employer, although I know the benefits.