Low and yellow urine is due to: first, insufficient water intake or excessive fluid loss, resulting in concentrated urine, which will result in yellow urine. Due to the lack of body fluid, the kidneys filter less, so the amount of urine produced will be less, and patients need to drink more water. If there are diseases with excessive water loss, such as fever, nausea, vomiting, diarrhea, etc., then appropriate rehydration treatment is needed to increase the urine volume, and the urine color can return to normal after the urine volume increases; secondly, patients with infectious diseases of the kidneys, such as nephritis, pyelonephritis or nephrotic syndrome, can have reduced urine volume. This is because the kidney filtration is reduced, so the patient’s urine volume is reduced, and at the same time, because the urine volume is too small, there can also be a deepening of the urine color. Or an infection may occur and the urine contains more bacterial metabolites and the urine pigment increases, so a yellowish urine color occurs. Kidney function tests, ultrasound of the kidneys and routine urine tests are needed to further confirm the diagnosis.