Four-month-old baby urine yellow may be caused by the baby sweating too much, may also be caused by taking vitamin B₂ and other drugs, or may be due to cystitis and so on. 1. Physiological factors: If the four-month-old baby sweats too much in the summer, the parents did not feed the baby water in a timely manner, it is possible to cause the baby to appear yellow urine performance, this situation does not need to worry too much, appropriate to the baby to feed water can be. 2. medication: vitamin B₂ is also called riboflavin, if the parents give the child supplemental vitamin B₂, resulting in vitamin B₂ from the urinary excretion, there will be a four-month-old baby urine yellow symptoms. 3. cystitis: cystitis can lead to hematuria in babies, so the symptom of yellow urine in four-month-old babies can also occur, in addition to the baby will also have symptoms such as crying and restlessness, fever and so on. After eliminating the physiological factors, if the symptoms of yellow urine in four-month-old babies continue to be unrelieved, it is recommended to consult a doctor in time to find out the cause and ask the doctor to be disposed of.