Yellow urine in five-month-old babies may be a normal physiological phenomenon, but it may also be caused by dehydration or urinary tract infection. 1. Physiological phenomenon: If the baby’s morning urine is slightly yellow and there is no other discomfort, it may be caused by the concentration of urine at night, which is usually normal. 2. dehydration: if the baby urine yellow at the same time the number of urination is also reduced, it may be due to dehydration, parents can give the baby appropriate increase in the amount of water and the number of times, the symptoms of yellow urine will usually be better. 3. urinary tract infection: if the baby urine yellow and other discomfort manifestations, such as the baby crying, loss of appetite, fever, and the symptoms of frequent urination, the consideration may be caused by urinary tract infection, can go to the hospital to do urinalysis and other related tests to clarify the diagnosis. Five-month-old baby yellow urine may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.