What should you know about occult blood in urine?

A urine test may detect red blood cells or haemoglobin even when urine looks normal. Causes include a urinary tract infection, kidney infection, kidney stones, inflammation of the prostate, or an enlarged prostate. Strenuous exercise, menstrual blood entering the sample, and collection problems can also affect the result. Less common but important causes include bladder or prostate disease, so visible or repeated blood should not be ignored. The result alone does not show where the blood came from or whether a serious condition is present. Burning urine, frequent urination, fever, flank pain, or difficulty passing urine provide useful clues.

Tell the clinician about urinary symptoms, recent exercise, menstrual bleeding, injuries, medicines, and previous results. You may be asked to provide a clean midstream sample, and the urine may be checked for infection. Depending on your age, symptoms, and medical history, further blood tests, imaging, or specialist review may be considered. Do not start leftover antibiotics, because treatment depends on the cause and an infection may need testing first. Keep hydrated unless a clinician has told you to restrict fluids.

Seek urgent care for heavy visible bleeding, clots, inability to pass urine, severe one-sided back or flank pain, fever with shaking chills, vomiting, faintness, or feeling acutely unwell. Arrange medical review for any unexplained visible blood or a result that persists on repeat testing, even if you feel well.

Ask whether the sample should be repeated, whether infection testing is needed, how your medicines or prostate may affect the result, and what follow-up is appropriate if blood remains detectable.