There is a smell of ammonia in fresh urine, the possible causes are as follows: 1, the presence of chronic urinary retention, such as urine in the bladder for more than three hours, this will cause the decomposition of protein in the urine and produce a certain ammonia, urination can appear to have an ammonia odor, more suggests the presence of urinary retention, it is recommended that the bladder residual urine measurement to confirm the diagnosis of the presence of urinary retention. There are many reasons for urinary retention, male prostate hyperplasia or urethral stricture may lead to urinary retention; 2, the presence of urinary tract infection, the presence of more bacteria in the urine after infection, easy to decompose some protein components in the urine, then the protein decomposition can produce ammonia, dissolved in the urine with the urine elimination will appear a smell of ammonia, it is recommended to carry out routine urine examination and culture examination 3, long-term meat or acidic diet, high-protein diet patients can cause increased trace protein content in the urine, then protein decomposition can produce ammonia, resulting in ammonia odor.