The common causes of yellowish urine include drinking too little water, diet-related, urinary tract infections, and kidney diseases. 1. Drinking too little water: drinking less water makes the body in a state of dehydration, resulting in increased water reabsorption, reduced discharge, urine concentration. This will cause a decrease in urine volume, and the color of urine will be obviously yellow. 2. Diet-related: a large number of carrots, oranges and other foods, due to the food is rich in carotene, riboflavin, such as at the same time insufficient water intake, there will be urine less yellow urine. 3. Urinary system infection: if there is an infection of the urinary system, there are more bacterial metabolites in the urine, increased pigmentation, there will also be urine less yellow. 4. Kidney disease: If you suffer from kidney disease, such as glomerulonephritis, acute nephritis, etc., resulting in reduced renal filtration, there can be a decrease in urine volume, yellow color. If there is a decrease in the amount of yellow urine, you should go to the hospital in time to get a clear diagnosis and timely treatment, so as not to delay the condition.