In 2001, state prisons held 4,106 inmates. By 2008, they held 6,097.
With the opening of a new 388-bed facility in Salem, a converted juvenile detention center, Rubenstein said he'll likely have to ask lawmakers for more medical services funding next year.
But even as overall costs rose during 2001-08, Rubenstein said per-inmate expenses dropped slightly, by about $200 per inmate, because of collaboration with prison health-care contractor Wexford Health Services.
The changes have included limiting hospital trips and treating more problems in the infirmaries, and providing some dental, optical and diagnostic services in the prisons.
In Texas, Schiff said prisons have increased their use of medical Internet teleconferencing with sick inmates, saving the state about $780 million between 1994 and 2008.
Other states are enrolling prisoners in Medicaid, although the benefits are limited.
Medicaid can cover prisoners' costs at nursing homes or hospitals when they are admitted for more than 24 hours, but that gives the state the chance to get at least some reimbursement.