The erythrocyte (red blood cell) test is a blood analysis performed to determine the amount of red blood cells in the blood. This test is typically reported as the RBC (Red Blood Cell) value within a Complete Blood Count (CBC). Erythrocytes can also be evaluated in urine tests. The presence of erythrocytes in urine (hematuria) means there is blood in the urine. This condition can be an indicator of medical conditions such as kidney stones, urinary tract infections, or other serious disorders related to the urinary system. However, the presence of erythrocytes in urine does not always indicate a serious illness. The consumption of some red-colored vegetables or fruits, lead or mercury poisoning, the use of certain bowel-softening medications, or some antibiotics can also be among the factors leading to the appearance of erythrocytes in urine. In summary, erythrocyte levels are an important parameter that can be examined through both blood and urine tests.