Abbreviation for hematocrit count, or the ratio, by volume, of red blood cells in a CBC (Complete Blood Count) blood sample, expressed as a percentage. Normal ranges for hematocrit values are 37-48% for women and 42-52% for men. People going through kidney failure typically suffer depressed crit counts. One of the thousands of terms thrown around on the television series ER without ever actually being defined. If you're like me, you occasionally use E2 instead of Google or AltaVista to find the answers to questions like "Gee, they're using that crit word a lot, and the patient they're treating seems to be dying because of it. I wonder what it means..." Well, now you (and I) know. I'm really not trying to turn E2 into a medical dictionary here, I promise. But, now you can go and watch ER in peace.