What is Agglutination? by Gary Cecchi, M.D. Agglutination occurs when incompatible blood types are mixed together and blood cells begin to clump. Each blood cell contains large protein molecules called antigens on its surface. Blood also contains antibodies, which bind to foreign antigens and cause incompatible blood cells to burst or agglutinate. In humans, blood agglutination can cause kidney failure and death. Medical practitioners are therefore very careful when giving blood to patients. Despite their caution, however, approximately one out of every 12,000 units of blood transfused in the United States goes to the wrong person. Depending on the blood types involved, the results can range from catastrophic to unnoticeable. About the Author: Managing Partner of Northern California Hematology and Oncology Dr. Gary Cecchi possesses years of experience as a hematologist. He has served as the Director for Hematology and Medical Oncology at Alta Bates Summit Medical Center and holds board certification in both hematology and oncology.