The feeling of having the urge to urinate is sometimes light and sometimes heavy, which may be some physiological phenomenon or the manifestation symptom of certain diseases, such as bladder stones, prostatitis, etc., and you should consult a doctor in time to find out the cause of the disease. 1. physiological factors: due to a large amount of water consumption leads to an increase in the desire to urinate, while a small amount of water consumption will lead to a decrease in the desire to urinate. 2. Pathologic factors: (1) Bladder stones: symptoms such as lower abdominal pain, difficulty in urination and hematuria often occur; if they irritate the bladder wall or form friction with the bladder mucosa, only then will they lead to involuntary contraction of the bladder, and so there will be light and heavy urge to urinate. (2) Prostatitis: Because the enlarged prostate gland will be directly upward to the bladder body, which will easily cause the activation of the volume receptor in the bladder, and the patient will have a stronger urge to urinate, and the symptom will be relieved when the experience is changed, so the urge to urinate is sometimes light and sometimes heavy. There may be other reasons why the urge to urinate is sometimes light and sometimes heavy, so it is recommended to actively seek medical advice and treatment under the guidance of a professional physician.