Requesting a change to conference lodging before accommodations have been verified? I have applied and been accepted to a conference as a graduate student attendee (not presenting any material). They were able to give lodging and promised to reimburse a good portion of travel which is all very good and I am very grateful. However, when I applied for the conference I indicated that I would be O.K. sharing  a hotel room. Unfortunately I have an medical situation that is better at some times than others and it's been rather poor since I first applied to the conference. Realistically if I'm going to attend the conference I'd need my partner to come with me to help with that situation which means we'd need to share a room and I couldn't share a room with another attendee. What is the most professional and effective way to make this request? 

I always prefer to say as little about my medical situation as possible particularly because the folks organizing this conference run a Department I'm interested in for my PhD. They have not made lodging arrangements yet but made it clear they will need to make them by tomorrow so really I have about 1 day to request a lone room before they go and make arrangements. Thanks y'all for any tips on approaching this!
The best way is just to be direct, though you may need to reveal a bit about the reasons. Explain the situation much as you have here. I think most conferences would try to accommodate you, but it might not work out in every situation, due to numbers and money. 

But do this immediately, so that it doesn't require reassignment of rooms, etc. 

Alternatively, if you are willing to pay for your own accommodations and feel that is worth it for preserving your privacy, you can just decline the offer and make your own reservation. It might be best to work with the conference, however, as they may have access to special rates for attendees. 

Universities in the US are not, in general, allowed to discriminate against people for medical conditions, so I wouldn't be overly concerned about revealing that you have a medical issue, leaving out details as you see fit.