My 15 year old daughter has been having some problems with her periods. We took her to an adolescent doctor recommended by our endocrinologist. While there, she had a urine test which showed “moderate amounts of blood”. The doctor wants us to have another urine test done. What could cause blood in urine if all other tests came back normal? She did not have her period at the time and was not due for it until 10 days later, so it was not from that. Any information you can give me would help. I’m very concerned.

The urine chemical tests for blood are pretty sensitive but not necessarily specific. That means that tiny, tiny, microscopic amounts of “blood” can be detected, but what reacts with the test may not, in fact, be blood. The test commonly is trying to detect hemoglobin, a component of blood. But “myoglobin”, a related protein, can also react with the test. Special tests, including having the urine examined under the microscope by laboratory personnel can help make the distinction.

But, what if it really is blood? Despite the history, it could still be vaginal blood; it could be blood from the bladder or kidneys; it could be blood from the skin around the urethra if she cleaned the area vigorously just before the urine collection. So, there are many, many possibilities, including laboratory error, which may be non-worrisome. Certainly, there could be more bothersome things too, but not too common in a teenage girl.

I’d follow up with the next round of testing and then decide if I needed to worry more.

Finally, please ask your doctors about your questions as they have more specifics about what they found with your daughter.

DS