The most common reason is prostate hyperplasia if you are a male. And as you get older, the more hyperplastic you are, the heavier the symptoms of fine urine and weakness are manifested. When prostate hyperplasia occurs, the gland protrudes into the urethral cavity and bladder cavity, causing the urethra to become thin. And the resistance of the urethra increases, and the bladder needs to overcome more resistance when urinating, so it will produce weakness in urination. Ultrasound examination of the prostate is needed, and surgery is required if necessary.2. If there are tumors, polyps, stones and other changes in the urethra, this can lead to urethral obstruction and the symptoms of thinning and weakness of urination. At the same time, it may be accompanied by pain in the urethra, bleeding in the urethra and other symptoms, which usually start more rapidly. When sudden urinary urgency, thin urination and weakness of urination occur, urethroscopy is needed to clarify the presence of polyps, tumors, stones and other lesions.