Stabilizing compositions for stabilizing a post-phlebotomy, but pre-analysis, blood samples include a metabolic inhibitor, a protease inhibitor, a buffer system, an anticoagulant, and a solvent. The stabilizing compositions stabilize a post-phlebotomy blood sample to preserve the physiological state of the blood sample for later analysis. The analysis performed on the stabilized blood sample may determine the state of an analyte in a blood sample for diagnosis. The stabilizing compositions may stabilize the post-phlebotomy blood sample for at least 6 hours, and up to 672 hours. More preferably, the stabilizing composition has an undetectable level of formaldehyde before contact with the post-phlebotomy blood sample, so that cross linking of proteins and cross linking of proteins to nucleic acids in the post-phlebotomy blood sample is minimized. The stabilizing composition has a test sensitivity rate of 1 for up to 672 hours.
