Abstract: A process and preservatives for preventing glycolysis in blood samples so as to preserve the glucose content and lactic acid content thereof. The preservatives do not produce any significant hemolysis in the blood sample, and they do not interfere with any of the known blood constituents. The preservatives comprise salts of Iodoacetic acid, such as Tris-Iodoacetate [(CH.sub.2 OH).sub.3 NH.sub.3 CO.sub.2 -- CH.sub.2 I]; salts of Bromoacetic acid, such as Tris-Bromoacetate [(CH.sub.2 OH).sub.3 NH.sub.3 CO.sub.2 -- CH.sub.2 Br], or Sodium Bromoacetate [NaO.sub.2 CCH.sub.2 Br]; and salts of mono Chloroacetic acid (ClCH.sub.2 COOH), such as Sodium Chloroacetate (NaO.sub.2 CCH.sub.2 Cl).