Urine Blood (Hematuria)
Urine Blood· also: Blood in Urine, Urine Blood, RBC urine
Clinical Overview
Hematuria (blood in urine) can be gross (visible to the naked eye — pink, red, or brown urine) or microscopic (visible only on dipstick or microscopy). The urine blood dipstick detects hemoglobin and myoglobin through a peroxidase reaction. Any unexplained hematuria — especially in adults over 35 — requires thorough evaluation to exclude urinary tract malignancy, even if the cause appears benign.
Why This Test Matters
Hematuria is a clinically significant finding with a broad differential diagnosis. The three most clinically urgent causes to exclude are: (1) Urologic malignancy (bladder cancer, renal cell carcinoma, urothelial cancer) — painless gross hematuria in a smoker over 50 is bladder cancer until proven otherwise. (2) Glomerulonephritis — RBC casts on microscopy and proteinuria with hematuria point to glomerular disease. (3) Renal or ureteral stones — typically painful (renal colic). Microscopic hematuria (≥3 RBCs per high-power field on microscopy) in a non-menstruating adult with no identifiable benign cause (UTI, vigorous exercise, urethral trauma) requires urologic evaluation (cystoscopy and upper tract imaging). The AUA guidelines recommend evaluation of all adults with microscopic hematuria above age 35 to exclude bladder cancer.
Reference RangesWHO/IFCC standards
| Reference Range | Unit | Notes |
|---|---|---|
| Negative / Non-reactive | qualitative | Negative = normal; <3 RBC/HPF on microscopy |
Also reported in: RBC/HPF.
What Causes Abnormal Results?
High Urine Blood Causes
- Urinary tract infection (UTI) — most common cause in women
- Kidney stones (nephrolithiasis/ureterolithiasis) — often painful hematuria
- Bladder cancer — typically painless gross hematuria in older smokers
- Glomerulonephritis (IgA nephropathy most common — presents as hematuria often after respiratory illness)
- Vigorous exercise (runner's hematuria — transient, resolves with rest)
- Benign prostatic hyperplasia (BPH) in older men
- Renal cell carcinoma (kidney cancer)
- Anticoagulant therapy (warfarin, rivaroxaban, apixaban) — but never explains hematuria completely; always investigate underlying cause
- Trauma to urinary tract
- Polycystic kidney disease
Low Urine Blood Causes
- False-positive dipstick: myoglobinuria (rhabdomyolysis — urine appears red/brown without actual RBCs), hemoglobinuria (hemolytic anemia)
- False-negative: vitamin C (ascorbic acid) can inhibit dipstick peroxidase reaction
Signs & Symptoms to Watch For
How to Prepare for This Test
Collect midstream urine sample to avoid contamination. Women should not collect during menstruation. Confirm hematuria on microscopy (≥3 RBC/HPF on 2 of 3 properly collected specimens) before initiating an extensive workup. Vigorous exercise within 48 hours should be excluded as a cause before further evaluation.
Factors That Can Affect Results
- Myoglobin from rhabdomyolysis (muscle breakdown) causes false-positive dipstick blood (but microscopy shows no RBCs)
- Hemoglobin from hemolytic anemia causes false-positive dipstick blood (no RBCs on microscopy)
- Menstrual contamination in female samples
- High-dose vitamin C (ascorbic acid) causes false-negative blood dipstick
- Povidone-iodine contamination causes false-positive
- Beets and rhubarb cause red/pink urine without hematuria (beeturia)
- Some antibiotics (rifampicin) and foods (senna) can cause red-orange urine
Related Topics
Frequently Asked Questions
I noticed blood in my urine — should I go to the emergency room?
Gross (visible) blood in urine always requires prompt medical evaluation — same day or emergency room if accompanied by: severe pain (possible stone), inability to urinate, signs of infection (fever, shaking chills), or if you are on blood thinners. If gross hematuria is painless and you are over 40, see a urologist urgently — painless gross hematuria is a classic presentation of bladder cancer. Even if the bleeding stops, it must be evaluated because intermittent bleeding is characteristic of bladder tumors. Microscopic hematuria (found on a routine test without visible discoloration) also requires follow-up but is not an emergency.
My urine dipstick shows blood but the microscopy shows no RBCs — what does this mean?
This "dipstick positive, microscopy negative" pattern suggests either myoglobinuria or hemoglobinuria — both of which contain heme compounds that react on the dipstick peroxidase test without RBCs being present. Myoglobinuria occurs in rhabdomyolysis (muscle breakdown from crush injury, extreme exercise, statins overdose, compartment syndrome) and produces dark brown/red urine. Hemoglobinuria occurs in intravascular hemolysis (transfusion reactions, PNH, sickle cell crisis, HELLP syndrome). Both conditions can cause acute kidney injury and require urgent evaluation. If dipstick is positive for blood and microscopy is negative, check CK (creatinine kinase) for rhabdomyolysis.