A plus sign in the urine test for occult blood generally indicates the presence of hematuria, but it may also be myoglobinuria. The main test for occult blood in urine is hemoglobin and myoglobin, which are found in red blood cells. If red blood cells are present in the urine and the red blood cells are damaged, releasing the hemoglobin in them, a positive urine occult blood can be detected in the urine. Therefore, the presence of occult blood in the urine mostly indicates that the patient may have hematuria, which is more common in chronic nephritis, occult nephritis, etc. If urinary ultrasonography is performed to exclude stones and tumors, it is more supportive of nephritis. The presence of occult blood in the urine, in addition to hemoglobinuria, may also be myoglobinuria. Myoglobin is mainly found in muscles. If the patient has rhabdomyolysis, the muscles release myoglobin, which will be excreted in the urine and can be detected as positive urine occult blood.