What does the positive or negative sign for red blood cells and occult blood in urine mean?

The result is ± (positive/negative). When a routine urinalysis shows ± for occult blood in red blood cells, it indicates a small number of red blood cells are present in the urine. The detailed analysis is as follows:

Normally, urine contains no red blood cells, although a few may occasionally be present. If a routine urinalysis reveals ± for red blood cell occult blood, this generally means there are a small number of red blood cells in the urine. This may be related to menstruation or strenuous exercise and is often a normal phenomenon, but it could also indicate an underlying medical condition. For women during their menstrual period, menstrual blood can mix with urine, resulting in a small number of red blood cells. After intense physical activity, exercise-induced hematuria may occur, which is a normal physiological response; symptoms typically resolve with increased fluid intake and frequent urination. However, if conditions such as acute cystitis, ureteral stones, bladder stones, or kidney tumors are present, cellular damage in the kidneys may impair filtration function, leading to the appearance of a small number of red blood cells in urinalysis.

If physiological factors have been ruled out, patients should visit a hospital for further examinations—such as kidney CT scan or kidney ultrasound—to accurately identify the underlying cause and receive timely, targeted treatment.