5-year-old boy drinking too much water after frequent urination may be a normal physiological phenomenon, or consider the bladder infection, urethritis and other diseases. 1. Normal physiological phenomenon: If a 5-year-old boy drinks too much water, due to excess water in the body, it will lead to an increase in urine volume, frequent urination. This phenomenon is normal, no need to worry too much. 2. Cystitis: Cystitis may be caused by bacteria, drugs, chemicals, sexually active and other factors. Patients may experience symptoms such as frequent urination, urgency, pain, burning sensation in the urethra, etc. Patients may experience frequent urination after drinking a lot of water. 3. Urethritis: Urethritis is mainly caused by gonococcal and non-gonococcal pathogen infection. Symptoms such as frequent urination, painful urination, increased urethral discharge, etc., manifested as frequent urination after drinking a lot of water in a 5-year-old boy. There are many causes of frequent urination after drinking a lot of water in a 5-year-old boy, and parents are advised to bring their children to regular hospitals to find out the cause of the disease. Once the diagnosis is confirmed, relevant treatment measures should be taken in time to avoid delaying the condition.