If there is a small amount of foam in the urine, the possible causes are: 1. The foam will increase when the urine is concentrated, and the foam will usually dissipate quickly. It is common in patients who drink less water or sweat more, resulting in concentrated urine, and can be accompanied by yellow urine. 2, if the protein content in the urine increases, there can be foam, mostly fine foam, which lasts longer. A routine urine test is needed to find out if there is an increase in urine protein.3. If the level of bilirubin and urobilinogen in the urine is elevated, foam can also appear, mostly yellow, and dissipate quickly. The amount of foam can be reduced after drinking more water appropriately.4. If a patient has high urine sugar, there can also be increased foam in the urine. Testing of blood sugar level and urine sugar level is needed to further confirm the diagnosis.5. If urine is shaken with water during urination, a little foam can be produced. If you stand at a high place to urinate, a little foam can be produced, this foam can dissipate quickly and is not caused by abnormal urine composition.