Cal. Penal Code § 4351

Any prisoner, to whom this chapter applies, may voluntarily donate blood to a blood bank duly licensed by the State Department of Public Health. Prior to blood donation the prisoner shall be given an examination with all clothes removed by a physician and surgeon of the blood bank to whom blood is to be donated, and donations shall be refused unless such physician shall find the prisoner to be a suitable person for blood donation. No more than one such donation shall be permitted during any 72-day period.