How long does it take for 4mm kidney stones to be discharged needs to be judged according to the actual situation, there are individual differences, in general, 4mm kidney stones need about 2 to 4 weeks to be discharged from the body. 4mm kidney stone can be through drinking more water, more exercise, small stones may follow the urine out of the body, but also under the guidance of the doctor to take sodium hydrogen potassium citrate granules and tamsulosin and so on to help discharge stones, 2 to 4 weeks after the hospital ultrasound examination of the urinary system to check whether the stone has been discharged. If it is accompanied by ureteral stenosis, combined with urinary tract infection, the stone discharge will take longer time or even can not be discharged, and when the symptoms are serious, we need to consult the doctor in time for examination and treatment. It is recommended to drink more water, more urination, the urethra has a flushing effect, to help discharge stones, avoid sedentary, appropriate exercise.