What does 1 blood in urine mean?

Blood +1: If there 1+ blood it is entering your urine in some way. Are there symptoms like burning with urine, flank pain, recent infection, etc? In females this is common with recent period. Labs use a convention with a scale: 0, trace, +1 to +4 for blood and other substances. See your doctor for further follow up as this needs to be looked at in a clinical context to be sure everything is good.