You might have blood in your urine and not notice it until it's too late. This microscopic issue can turn in a big problem, signs or traces of blood in the urine could mean something benign or something more dangerous. Your medical provider will test your urine if you are having certain symptoms or to rule out certain issues if the blood in the urine is not visible. Dr. Fazil explains what are some causes for this and what could be done to fix these issues and prevent them from becoming dangerous.