The reasons why babies urinate less after fever are as follows: a. After the baby’s fever, appetite decreases, eating less, drinking less, urine volume decreases, some babies have fever accompanied by vomiting, thin stools, etc., and more water is lost, resulting in less urine. After fever, metabolism is fast, and the body consumes more water, causing the body to be dehydrated, resulting in less urine and yellow urine. The baby’s body temperature rises after fever, and more body water evaporates, resulting in less urine. Second, you need to observe whether there are urinary system diseases, such as urinary tract infection, manifested as urine less, frequent and painful urination, etc., which can be further ruled out by urine routine test, and glomerulonephritis or nephrotic syndrome, in addition to urine less, there are eyelid and double lower limbs swelling, hematuria, etc.