Medical Disclaimer
  • For Educational Purposes Only: This content is intended for educational reference and should not be used for clinical decision-making.
  • Not a Substitute for Professional Judgment: Always consult your local protocols, institutional guidelines, and supervising physicians.
  • Accuracy Not Guaranteed: While all content has been prepared to the best of my knowledge and ability, errors or omissions may exist.
  • Verify Before Acting: Users are responsible for verifying information through authoritative sources before any clinical application.
AI Assistance Notice
The clinical content and references are curated and reviewed by myself; however, AI was used to assist in organizing, paraphrasing, and formatting the information presented.
Quick Reference
  • Normal Range: Negative
  • Detection Method: Dipstick colorimetric reaction
  • What It Detects: Hemoglobin, myoglobin, and intact RBCs
  • Primary Use: Screening for hematuria from urinary tract disease, trauma, or systemic conditions
  • Sample Type: Random or clean-catch urine specimen
  • Key Point: Positive dipstick requires microscopy confirmation to differentiate true hematuria from hemoglobinuria or myoglobinuria

Test Description

The urine blood dipstick test is a screening tool that detects the presence of blood in urine through a colorimetric reaction with the peroxidase-like activity of hemoglobin, myoglobin, and intact red blood cells. The test reagent pad contains organic peroxide and chromogen that produces a color change ranging from yellow (negative) to green to dark blue (positive) in the presence of heme-containing compounds.

Unlike other urine dipstick tests that are semi-quantitative, the blood test is highly sensitive and can detect as few as 1-2 RBCs per high-power field or 0.015-0.062 mg/dL of free hemoglobin. However, the test cannot distinguish between intact red blood cells (hematuria), free hemoglobin (hemoglobinuria), or myoglobin (myoglobinuria), making microscopic examination essential for proper interpretation.

Clinical Significance

Hematuria can be classified as:

  • Glomerular hematuria: Associated with kidney disease, characterized by RBC casts and dysmorphic RBCs on microscopy
  • Non-glomerular hematuria: From urinary tract bleeding (kidney stones, infection, trauma, malignancy)
  • Pseudohematuria: Positive dipstick without RBCs on microscopy, indicating hemoglobinuria or myoglobinuria
Normal Ranges

The urine blood dipstick should be negative in healthy individuals. Microscopic examination of normal urine may show 0-2 RBCs per high-power field (HPF).

Swipe to see more
Test Result Dipstick Reading Interpretation
Negative No color change Normal - no detectable blood
Trace Light green ~5-10 RBCs/HPF or minimal hemoglobin
Small (1+) Green ~10-25 RBCs/HPF
Moderate (2+) Dark green ~50 RBCs/HPF
Large (3+) Blue ~250 RBCs/HPF or gross hematuria
Important Considerations:
  • Dipstick results are qualitative/semi-quantitative and require microscopy confirmation
  • False positives and false negatives are common - always correlate with microscopy
  • Contamination with menstrual blood is a frequent cause of positive results in females
  • Any positive result in males or non-menstruating females warrants further investigation
Clinical Significance

Causes of Positive Urine Blood

A positive urine blood dipstick can result from true hematuria (intact RBCs), hemoglobinuria (free hemoglobin), or myoglobinuria (myoglobin).

Urinary Tract Causes

  • Urinary tract infection (UTI): Bacterial cystitis, pyelonephritis, or urethritis causing mucosal inflammation and bleeding
  • Kidney stones (nephrolithiasis): Ureteral or renal calculi causing mechanical trauma to urinary epithelium
  • Trauma: Blunt or penetrating injury to kidneys, bladder, or urethra
  • Malignancy: Bladder cancer, renal cell carcinoma, urothelial carcinoma (especially concerning in patients >35 years)
  • Benign prostatic hyperplasia (BPH): Prostatic bleeding in older males

Glomerular Causes

  • Glomerulonephritis: IgA nephropathy, post-streptococcal GN, lupus nephritis, membranoproliferative GN
  • Vasculitis: Granulomatosis with polyangiitis (Wegener's), microscopic polyangiitis, Goodpasture syndrome
  • Hereditary nephritis: Alport syndrome, thin basement membrane disease

Systemic Causes

  • Coagulopathy: Anticoagulant therapy (warfarin, heparin, DOACs), thrombocytopenia, hemophilia
  • Hemolysis: Hemoglobinuria from intravascular hemolysis (transfusion reaction, sickle cell crisis, hemolytic anemia)
  • Rhabdomyolysis: Myoglobinuria from muscle breakdown (trauma, strenuous exercise, statins, seizures)
  • Strenuous exercise: "March hematuria" from repetitive bladder trauma or transient glomerular injury

Other Causes

  • Menstrual contamination: Most common cause of false positive in menstruating females
  • Sexual activity: Urethral trauma or contamination with vaginal blood or semen
  • Catheterization: Trauma from Foley catheter insertion or prolonged indwelling catheter

Differentiating Glomerular vs Non-Glomerular Hematuria

Microscopic examination helps distinguish the source of bleeding:

  • Glomerular hematuria: RBC casts, dysmorphic RBCs (>20% acanthocytes), proteinuria, no clots
  • Non-glomerular hematuria: Uniform RBCs, possible clots, minimal or no proteinuria
RBC Casts: Pathognomonic for glomerulonephritis. Formed when RBCs become trapped in tubular protein matrix, indicating bleeding from glomerulus with subsequent tubular transit.
Interpretation Guidelines

Diagnostic Approach to Positive Dipstick

Step 1: Confirm with Microscopy

  • Positive dipstick + RBCs on microscopy = True hematuria (investigate cause)
  • Positive dipstick + NO RBCs on microscopy = Hemoglobinuria or myoglobinuria (investigate hemolysis or rhabdomyolysis)
  • Negative dipstick + RBCs on microscopy = Rare; consider ascorbic acid interference or dilute urine

Step 2: Assess for Contamination

  • Recent menstruation in females (obtain clean-catch midstream or catheterized specimen)
  • Recent sexual activity or vigorous exercise (repeat testing after 48-72 hours)
  • Improper specimen collection (recollect with proper technique)

Step 3: Determine Source

  • Glomerular: RBC casts, dysmorphic RBCs, proteinuria, hypertension, renal insufficiency
  • Non-glomerular: Uniform RBCs, symptoms of UTI/stones, no casts, minimal proteinuria

Step 4: Further Workup Based on Clinical Context

  • If glomerular suspected: Serum creatinine, complement levels (C3, C4), ANA, ANCA, anti-GBM antibodies, renal biopsy
  • If non-glomerular suspected: Urine culture, renal ultrasound, CT urography, cystoscopy (especially if >35 years or risk factors for malignancy)
  • If hemoglobinuria suspected: CBC, peripheral smear, LDH, haptoglobin, direct Coombs test
  • If myoglobinuria suspected: CK, myoglobin level, comprehensive metabolic panel, urine myoglobin
Red Flags Requiring Urgent Evaluation:
  • Gross hematuria with clots (possible obstructive uropathy or malignancy)
  • Hematuria with acute kidney injury (possible rapidly progressive glomerulonephritis)
  • Hematuria with severe flank pain (possible kidney stone or renal infarction)
  • Painless hematuria in patient >35 years (rule out malignancy)
  • Positive dipstick with dark brown/tea-colored urine and no RBCs (possible rhabdomyolysis - check CK urgently)
Interfering Factors

False Positives (Positive Dipstick Without True Hematuria)

  • Hemoglobinuria: Free hemoglobin from intravascular hemolysis (transfusion reaction, hemolytic anemia, paroxysmal nocturnal hemoglobinuria)
  • Myoglobinuria: Myoglobin from rhabdomyolysis (trauma, prolonged immobilization, strenuous exercise, statins, cocaine use)
  • Menstrual contamination: Most common cause in pre-menopausal females; obtain clean-catch specimen or repeat after menses
  • Semen contamination: Recent sexual activity or nocturnal emission
  • Oxidizing contaminants: Hypochlorite (bleach), microbial peroxidases from severe UTI
  • Dehydration/concentrated urine: Can increase sensitivity and cause false low-level positives

False Negatives (Negative Dipstick Despite True Hematuria)

  • Ascorbic acid (vitamin C): High doses (>25 mg/dL) inhibit peroxidase reaction; common cause of false negatives
  • High specific gravity: Very concentrated urine may inhibit color development
  • Formalin contamination: Preservatives in specimen containers can inhibit reaction
  • Captopril and other reducing agents: May interfere with peroxidase reaction
  • Low pH: Very acidic urine (<5.0) may decrease sensitivity

Collection and Technical Factors

  • Delayed testing: RBC lysis in urine specimen left at room temperature >2 hours (may cause false positive for free hemoglobin)
  • Improper storage: Refrigerated specimens may preserve RBCs better but can cause crystallization
  • Contamination: Vaginal discharge, rectal contamination, povidone-iodine from skin prep
  • Strenuous catheterization: Traumatic insertion causing iatrogenic hematuria
Clinical Pearls
Clinical Pearl
"Positive dipstick + no RBCs on microscopy = hemoglobinuria or myoglobinuria": This classic finding should prompt immediate evaluation for hemolysis (check LDH, haptoglobin, peripheral smear) or rhabdomyolysis (check CK, urine myoglobin). Tea-colored or cola-colored urine suggests myoglobinuria from rhabdomyolysis.
Clinical Pearl
RBC casts = glomerulonephritis until proven otherwise: The presence of RBC casts on microscopy is pathognomonic for glomerular disease and requires urgent nephrology consultation. This finding indicates active glomerular inflammation with RBCs passing through glomerular basement membrane and becoming trapped in tubular casts.
Clinical Pearl
Dysmorphic RBCs suggest glomerular origin: If >20% of RBCs on microscopy are dysmorphic (irregular shape, blebs, fragmented), this suggests glomerular bleeding as RBCs are damaged passing through abnormal glomerular basement membrane. Acanthocytes (ring-form RBCs with vesicle-shaped protrusions) are most specific for glomerular disease.
Always rule out malignancy in older patients: Painless hematuria in patients >35 years (especially smokers) should be considered bladder cancer or renal cell carcinoma until proven otherwise. These patients require cystoscopy and CT urography regardless of normal initial imaging.
Menstrual contamination is very common: In menstruating females with positive urine blood, obtain clean-catch midstream specimen or catheterized sample. If contamination is still suspected, repeat urinalysis 1 week after menses ends. Do not dismiss hematuria as "just menses" without proper confirmation.
Clinical Pearl
Vitamin C can hide hematuria: Patients taking high-dose vitamin C supplements (>1000 mg daily) may have false-negative dipstick despite true hematuria. If clinical suspicion is high, proceed directly to microscopy or discontinue vitamin C for 48 hours and retest.
Clinical Pearl
"March hematuria" after exercise: Strenuous exercise (especially running, contact sports) can cause transient hematuria from bladder trauma or glomerular injury. Usually resolves within 24-72 hours. Persistent hematuria after rest requires full workup.
Anticoagulation does not cause hematuria - it reveals underlying pathology: Hematuria in anticoagulated patients still requires full investigation for urologic malignancy or other causes. Anticoagulation unmasks bleeding from pre-existing lesions rather than causing de novo hematuria.
Clots suggest non-glomerular bleeding: Glomerular bleeding does not produce clots (RBCs are typically lysed and do not aggregate). Presence of clots indicates lower urinary tract source (bladder, urethra) or upper tract bleeding (renal pelvis, ureter).
Clinical Pearl
Timing of hematuria helps localize source: Initial hematuria (blood at beginning of stream) suggests urethral source. Terminal hematuria (blood at end of stream) suggests bladder neck or prostatic source. Total hematuria (blood throughout) suggests bladder, upper tract, or glomerular source.
References
  1. Kratz, A., Ferraro, M., Sluss, P. M., & Lewandrowski, K. B. (2004). Laboratory reference values. New England Journal of Medicine, 351, 1548-1564.
  2. Lee, M. (Ed.). (2009). Basic skills in interpreting laboratory data. Ashp.
  3. Farinde, A. (2021). Lab values, normal adult: Laboratory reference ranges in healthy adults. Medscape. https://emedicine.medscape.com/article/2172316-overview?form=fpf
  4. Nickson, C. (n.d.). Critical Care Compendium. Life in the Fast Lane • LITFL. https://litfl.com/ccc-critical-care-compendium/
  5. Farkas, Josh MD. (2015). Table of Contents - EMCrit Project. EMCrit Project. https://emcrit.org/ibcc/toc/
Back to Urinalysis Panel All Lab Values