What is the test for a plaintiff to sue for medical malpractice under the Eighth Amendment?

Under the Eighth Amendment, plaintiffs must show "a substantial risk of serious harm" that presents an "excessive risk to inmate health or safety." Farmer, 511 U.S. at 834, 837. Such an "objectively intolerable risk of harm," id. at 846, requires that "the risk must be 'sure or very likely to cause serious illness and needless suffering.'" Baze v. Rees, 553 U.S. 35, 50 (2008) (emphasis omitted) (quoting Helling v. McKinney, 509 U.S. 25, 33 (1993)).