It depends on the severity of the illness and what the doctors recommend. Some of us have very clear blood-supported symptoms & get disability easily (like with lupus-induced kidney damage) and yet some have more elusive non-provable symptoms (like joint & muscle pain) and have a harder time with disability.
Also, there are several kinds of disability so it depends on country, state, length person worked, who disability insurer is, etc.
The first person they need to consult is their Dr -- if the Dr doesn't clearly say "this person cannot work", then it's a hard battle to wage -- but if the Dr says "you shouldn't be working, your symptoms show you can't work" then disability can come easily.
Lynnwood, Lupus & Sjogren's Moderator
"Life is far too important to be taken seriously" - Oscar Wilde