A 3-year-old baby with yellow urine should pay attention to whether the urine is usually yellow or has recently appeared. If your child’s urine is usually yellow, you should pay attention to any yellowing of the skin, and if necessary, you should go to the hospital to improve liver function and liver ultrasound tests. If your child has yellow urine in recent days, you should pay attention to whether the weather is too hot or too dry, causing excessive evaporation of water, resulting in concentrated urine and yellow urine, and increase the amount of water your child drinks. Poor appetite and low water intake can also cause yellow urine, especially in summer, when children may sweat more, have a poor appetite and eat less, which can lead to reduced urine volume and yellow urine. After finding out the cause, give timely and symptomatic treatment, appropriate hydration and improve the baby’s food.