Hematuria Refers to Red Blood Cells in Urine, Not Blood
No, having erythrocytes (red blood cells) in the blood is not hematuria—hematuria specifically refers to the presence of red blood cells in the urine. This is a fundamental distinction in medical terminology that is critical for proper diagnosis and management.
Definition and Diagnostic Criteria
Hematuria is defined as the presence of red blood cells in the urine, not in the blood. 1, 2
- Microscopic hematuria is defined as ≥3 red blood cells per high-power field on microscopic evaluation of urine specimens 1, 2
- Gross (macroscopic) hematuria is visible blood in the urine that can be seen with the naked eye 2
- Red blood cells are normally present in blood—this is physiologic and expected 1
Why This Distinction Matters Clinically
The presence of RBCs in urine (hematuria) triggers a completely different diagnostic algorithm than abnormalities of RBCs in blood:
- Hematuria evaluation focuses on urologic malignancies (bladder cancer, renal cell carcinoma), urolithiasis, infection, and glomerular disease 1, 2
- Blood RBC abnormalities would prompt evaluation for hematologic disorders, anemia, polycythemia, or hemoglobinopathies 3, 4
Common Pitfall to Avoid
Dipstick positivity for blood does not confirm hematuria—it must be verified with microscopic urinalysis showing ≥3 RBCs per high-power field on at least two of three properly collected specimens before initiating any hematuria workup 1, 2. Dipstick tests have only 65-99% specificity and can produce false positives from myoglobin, hemoglobin, or other substances 2.
Clinical Context
When RBCs are found in urine sediment, their morphology helps determine the source: