Frequent urination and low volume are commonly caused by the following factors: 1. Functional factors. Mental, psychological and other factors, such as anxiety, fear, high levels of mental tension, can cause frequent urination. The main characteristic is that frequent urination is obvious during the day and disappears at night after sleeping. 2. Pathological factors. Patients with frequent urination are mostly caused by reduced functional bladder capacity and reduced bladder compliance when the bladder outlet is obstructed leading to increased residual urine, such as prostatic hyperplasia, bladder neck contracture and other diseases. 3, urinary stones and infections, such as bladder stones, urethral stones, cystitis, urethritis and other diseases, are mostly accompanied by painful urination and urgency.