Urine Occult Blood

Aka: Urine Occult Blood, Urine Dipstick Blood, Urine Blood Test Strip

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II. Mechanism

  1. Dipstick detects RBC peroxidase activity

III. Interpretation: Normal

  1. Negative

IV. Interpretation: Positive (Urine Dipstick with blood)

  1. Dipstick blood must be confirmed with microscopic exam
  2. Dipstick detects blood down to 1-2 RBC/hpf
  3. See Microscopic Hematuria for confirmatory exam
    1. Diagnosis of Microscopic Hematuria: 3 RBCs/hpf
  4. Causes
    1. See Adult Microscopic Hematuria Causes
    2. See Hematuria in Children

V. Causes: False Positive occult blood on Urine Dipstick

  1. Dehydration
  2. Exercise
  3. Hemoglobinuria
  4. Myoglobinuria (e.g. Rhabdomyolysis)
  5. Non-urinary tract blood source (e.g. Menses, semen)
  6. Alkalotic urine (pH >9)
  7. Antiseptic solution

VI. Causes: False Negative occult blood on Urine Dipstick (uncommon)

  1. Captopril
  2. Vitamin C supplementation (large intake)
  3. Increased Urine Specific Gravity
  4. Urine pH 5.0 or less
  5. Proteinuria

VII. References

  1. Hitzeman (2022) Am Fam Physician 106(1): 27-35 [PubMed]
  2. Simerville (2005) Am Fam Physician 71(6): 1153-62 [PubMed]

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