Hospital visits and extended medical care are generally covered by the facility at no charge to the inmate. If someone needs to be transported to an outside hospital for treatment that cannot be handled on site, that cost does not come out of their commissary account.
Medication prescribed during a hospital stay or as part of ongoing treatment is typically provided without charge as well. The facility has a constitutional obligation to provide adequate medical care, and that obligation extends to necessary medications.
Where inmates do get charged is for routine sick call visits when a doctor or medical staff member comes to the facility. That copay is nominal, usually somewhere in the range of three to five dollars depending on the institution. It is deducted directly from the inmate's account when they request to be seen for a non-emergency medical issue.
For inmates with no money on their books, most facilities are prohibited from denying medical care based on inability to pay. The copay may be waived or the debt noted in their account without immediate collection. Emergency care in particular cannot be withheld regardless of account balance.
If your person has a chronic condition or ongoing medical needs, making sure they have a small amount of money on their books helps cover those routine visit copays without creating debt. Beyond that, hospital level care is handled by the facility and should not create a financial burden on the inmate or their family.