Can a 4mm kidney stone pass on it's own? or will it need to be broken up?

Could pass: A stone of the size you described could pass in urine. You need to follow your doctor's advice about follow up visits and tests. You may consult this site for information on this topic: https://uihc.org/health-library/kidney-stones For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.