Effects of Hemolysis on Clinical Specimens

Hemolysis due to the breakdown of red blood cells is important to the laboratory because it can have an effect on laboratory results.  The effects can be the result of products liberated from the red cells themselves, or due to interferences with laboratory analyzers.  This may vary from one test to another depending on the formulation of the reagent.

Hemolysis can occur in vivo (in the patient), due to a variety of medical conditions, including antigen-antibody reactions, hemolytic anemias, toxins and poisons, mechanical RBC rupture due to artificial heart valves, as well as treatments such as hemodialysis and the use of the heart-lung bypass machine.   Hemolysis can occur during suboptimal blood collection, or in vitro (e.g. in the collection tube) due to improper storage.

Hemolysis is graded as slight, moderate or gross.

  • Slight hemolysis has little effect on most test values. 
  • Gross hemolysis causes a slight dilutional effect on analytes present at a lower concentration in the red cells compared to plasma.  However, a marked elevation may be observed for analytes present at a higher concentration in red cells than in plasma.
  • Test results on specimens with slight hemolysis are usually processed.
  • Comments are attached indicating the degree of hemolysis.

Some tests are affected more than others.  Notable example of tests affected by hemolysis are found in the table below.

Effect of Hemolysis on some Clinical Biochemistry and Hematology Test Results


Degree of change in analyte

Test result increased by hemolysis


Test result decreased by hemolysis

Test result increased or decreased by hemolysis

Slight change

Phosphate, Total Protein, Albumin, Magnesium, Calcium, Alkaline Phosphatase (ALP)

Haptoglobin, Bilirubin


Noticeable change

ALT, CK, Iron, Coagulation tests

Thyroxine (T4)


Significant change

Potassium (K+), Lactate Dehydrogenase (LD), AST

Troponin T

HGB, RBC, MCHC, Platelet Count



Note:  If the specimen is grossly hemolyzed, a recollected specimen will be requested.  If the recollected specimen is also grossly hemolyzed, it will be processed and a comment added.