What is the legal test for deliberate indifference to serious medical needs under the Eighth Amendment?

S.Ct. 285, 50 L.Ed.2d 251] ["deliberate indifference to serious medical needs of prisoners constitutes the 'unnecessary and wanton infliction of pain' [citation] proscribed by the Eighth Amendment," which includes "indifference . . . manifested by prison doctors in their response to the prisoner's needs or by prison guards in intentionally denying or delaying access to medical care or intentionally interfering with the treatment once prescribed"]; Peralta v. Dillard (9th Cir. 2014) 744 F.3d 1076, 1082 ["[a] prison official is deliberately indifferent to [a serious medical] need if he 'knows of and disregards an excessive risk to inmate health'"].) "[S]ubjective recklessness as used in the criminal law is . . . the test for 'deliberate indifference' under the Eighth Amendment." (Farmer v. Brennan (1994) 511 U.S. 825, 839-840.)