All inmates have a Consitutional right to adequate medical care under the 8th Amendment to the Constitution. The Supreme Court has held that it is cruel and unusual punishment to deny an inmate necessary medical care.
If this particular inmate has a condition that requires hospital attention, while the prison does not have to provide the same caliber of medical care that he would get on the outside, they cannot turn a blind eye to his problems either.
You can get an idea of what courts have found to be deliberate indifference and what sorts of situations constitute a serious medical need here in this PDF, which was put together by the ACLU.
In my experience, friends and family members of a defendant are only going to get the runaround when they try to inquire too closely about what's going on with their incarcerated relatives, particularly when the questions relate to the inmate's treatment -- medical and otherwise -- at the hands of the Department of Corrections.
It takes a lawyer who does civil rights work to break that pattern. They not only can visit an inmate when family and friends cannot but they can get in touch with people in the system who will not speak at all to family and thus have a much better chance of turning the situation around. Contact the inmate's lawyer. He can put the prison on notice of a possible civil rights claim, which may help convince the prison authorities to hospitalize him. Or, he can get the inmate back in court where the judge can order appropriate medical treatment.
For something like this, you might also want to reach out to the ACLU. They have advocated for inmates all over the country for basic inmate rights. Even if they have too much on their plate to get involved directly in this situation, they have branches throughout the US and may know of civil rights lawyers in this inmate's vicinity who would offer assistance.
Their national website is at ACLU.org.