If the urine smells foul, then the possible causes are as follows: First, when the urine is concentrated or when the urine is held for a long time, there will be a heavy smell of foul urine. The concentrated state of urine, or the state of holding urine for a long time, can cause the decomposition of proteins in urine. Generate ammonia-like substances, so there will be a volatile odor. The abnormal smell in urine can disappear after drinking more water and urinating more, or urinating more. Secondly, when there is a urinary tract infection, bacteria decompose the proteins in the urine, which can produce ammonia and hydrogen ions, which will cause frequent and urgent urination, accompanied by a heavy urine odor, which requires routine urine examination, and is mostly accompanied by symptoms of urinary irritation or fever with a sense of urinary impurity. Thirdly, if you eat a high protein or meat diet, you can see an increase in amino acid content in the urine. The decomposition of amino acids can produce ammonia and hydrogen ions, resulting in a heavy smell of urine. You need to adjust the diet structure, meat and vegetarian mix, avoid long-term high protein, high meat diet.