What does trace of occult blood in urine mean?

It means: That altho no visible blood, chemically blood was detected in your urine. This is not usually normal. You may have an infection or a ureteral/kidney stone or some bladder inflammation or a tumor, so please get evaluated, diagnosed and properly treated.

Need more tests: Specifically, you need to have a urinalysis and urine culture by your doctor. If on two urinalyses, there are 3 or more red blood cells per high per field under microscope, then you will need a full workup. The workup includes urine cytology, imaging (ctscan usually), and camera to look inside the bladder (cystoscopy).