Heparin is the only anticoagulant that should be used in a blood collection device for the determination of pH, blood gases, electrolytes and ionized calcium. Heparin should not be used for coagulation or hematology testing. lithium heparin can be used for routine CBC counts in a clinical setting. The use of the same anticoagulant should be recommended to follow trends within the same patient, especially when considering plasma protein concentration, packed cell volume (PCV) and lymphocyte count.