The common reasons for 5-month-old babies to urinate less include: insufficient milk intake, fever, and loss of body fluids. 1. Insufficient milk: 5-month-old babies to change diapers about 6 times is appropriate, otherwise it may suggest that the milk intake is insufficient, a long time may lead to delayed growth and development, nutrient deficiencies, etc., need to parents to ensure that their babies feeding amount. 2. Fever: Fever is a common symptom in infancy and early childhood, which may be caused by bacterial or viral infections, etc. Fever will increase water loss, and babies will show a decrease in urine output. 3. Loss of body fluids: when the baby has diarrhea, vomiting and other symptoms, a large loss of body fluids, resulting in dehydration, manifested in decreased urine output, and in severe cases, dehydration and shock may occur. 5 months baby urine, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.