What is the test for a claim for deliberate indifference to serious medical needs?

To prevail on a claim for deliberate indifference to serious medical needs, a prisoner must demonstrate that a prison official "kn[ew] of and disregard[ed] an excessive risk to inmate health or safety; the official must both be aware of the facts from which the inference could be drawn that a substantial risk of serious harm exists, and he must also draw the inference." Farmer v. Brennan, 511 U.S. 825, 837 (1994).