The ASCP Board of Certification (BOC) publishes composite reference ranges for interpreting corresponding laboratory values on the Medical Laboratory Scientist examination. The ranges include all genders and ethnic populations and come from published sources such as textbooks. The ASCP BOC Hematology and Chemistry Examination Committees review them annually.1
Examination use
Use these ranges to prepare for the examination. They are not provided during the examination. When an item needs other reference ranges, the item supplies them. Examination laboratory values and ranges appear in conventional and SI units.1
The tables reproduce the values listed by ASCP BOC. Its SI units column also contains dimensionless results and laboratory reporting units. These include percentage, pH, specific gravity, nucleated red blood cells (NRBCs) per 100 white blood cells (WBCs), high-power field (HPF), low-power field (LPF), and Ehrlich unit (EU).
The ASCP BOC tables retain their source's rights and are excluded from LatticeMLS's Creative Commons license. The original explanations on this page use CC BY-NC-SA 4.0.
Chemistry
The chemistry ranges include electrolytes, renal markers, glucose control, haptoglobin, and arterial blood gases.1
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| Analyte | Conventional units | SI units |
|---|---|---|
| Sodium | 136–145 mmol/L | 136–145 mmol/L |
| Potassium | 3.5–5.1 mmol/L | 3.5–5.1 mmol/L |
| Chloride | 98–107 mmol/L | 98–107 mmol/L |
| Total CO2 | 22–33 mmol/L | 22–33 mmol/L |
| Creatinine | 0.8–1.2 mg/dL | 71–106 µmol/L |
| Blood urea nitrogen (BUN) | 6–20 mg/dL | 2.1–7.1 mmol/L |
| Glucose, fasting | 74–100 mg/dL | 4.1–5.6 mmol/L |
| Hemoglobin A1C | <5.7% | <39 mmol/mol |
| Haptoglobin | 30–200 mg/dL | 0.3–2.0 g/L |
| Arterial pH | 7.35–7.45 | 7.35–7.45 |
| Arterial pCO2 | 35–44 mm Hg | 4.7–5.9 kPa |
| Arterial pO2 | >80 mm Hg | >10.6 kPa |
| Arterial O2 saturation | >95% | >95% |
| HCO3-, bicarbonate | 23–29 mmol/L | 23–29 mmol/L |
Hematology
The hematology ranges combine genders and ethnic populations for examination use. Absolute cell counts appear in conventional and SI forms, and relative counts appear as percentages and decimal fractions.1
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| Analyte | Conventional units | SI units |
|---|---|---|
| Red blood cells (RBCs) | 4.00–6.00 × 106/µL | 4.00–6.00 × 1012/L |
| Hemoglobin (HGB) | 12.0–18.0 g/dL | 120–180 g/L |
| Hematocrit (HCT) | 35–50% | 0.35–0.50 L/L |
| Mean corpuscular volume (MCV) | 76–100 fL | 76–100 fL |
| Mean corpuscular hemoglobin (MCH) | 26–34 pg | 26–34 pg |
| Mean corpuscular hemoglobin concentration (MCHC) | 32–36 g/dL | 320–360 g/L |
| Red cell distribution width (RDW) | 11.5–14.5% | 0.115–0.145 |
| Reticulocytes, absolute | 20–115 × 103/µL | 20–115 × 109/L |
| Reticulocytes, relative | 0.5–2.5% | 0.005–0.025 |
| Nucleated red blood cells (NRBCs) | 0 NRBC/100 WBC | 0 NRBC/100 WBC |
| Platelets | 150–450 × 103/µL | 150–450 × 109/L |
| WBCs, total | 3.6–10.6 × 103/µL | 3.6–10.6 × 109/L |
| Neutrophils, absolute | 1.7–7.5 × 103/µL | 1.7–7.5 × 109/L |
| Neutrophils, relative | 50–70% | 0.50–0.70 |
| Lymphocytes, absolute | 1.0–3.2 × 103/µL | 1.0–3.2 × 109/L |
| Lymphocytes, relative | 18–42% | 0.18–0.42 |
| Monocytes, absolute | 0.1–1.3 × 103/µL | 0.1–1.3 × 109/L |
| Monocytes, relative | 2–11% | 0.02–0.11 |
| Eosinophils, absolute | 0–0.3 × 103/µL | 0–0.3 × 109/L |
| Eosinophils, relative | 1–3% | 0.01–0.03 |
| Basophils, absolute | 0–0.2 × 103/µL | 0–0.2 × 109/L |
| Basophils, relative | 0–2% | 0.00–0.02 |
Body fluids and urine
The ASCP BOC table gives separate ranges for cerebrospinal fluid (CSF), seminal fluid, urine chemistry, and urine microscopy.1
Cerebrospinal fluid
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| Test | Conventional units | SI units |
|---|---|---|
| WBCs and RBCs | 0–5/µL | 0–5 × 106/L |
| Glucose | 50–80 mg/dL | 2.8–4.4 mmol/L |
| Protein | 15–45 mg/dL | 150–450 mg/L |
Seminal fluid
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| Test | Conventional units | SI units |
|---|---|---|
| Liquefaction | 30–60 minutes | 30–60 minutes |
| WBCs | <1 × 106/mL | <1 × 109/L |
| Volume | 2–5 mL | 2–5 mL |
| pH | 7.2–8.0 | 7.2–8.0 |
| Motility | >50% within 1 hour | >50% within 1 hour |
| Sperm concentration | >20 × 106/mL | >20 × 109/L |
| Morphology | >30% normal forms | >30% normal forms |
Urine
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| Test | Conventional units | SI units |
|---|---|---|
| Specific gravity | 1.003–1.035 | 1.003–1.035 |
| pH | 4.5–8.0 | 4.5–8.0 |
| Protein | <10 mg/dL, trace, or negative | <0.1 g/L, trace, or negative |
| Bilirubin | Negative | Negative |
| Blood | Negative | Negative |
| Glucose | 15 mg/dL or less, or negative | 0.8 mmol/L or less, or negative |
| Nitrite | Negative | Negative |
| Leukocyte esterase | Negative | Negative |
| Urobilinogen | <1.0 EU | <17.0 µmol/L |
| Ketones | <5 mg/dL or negative | <0.5 mmol/L or negative |
Urine microscopy
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| Finding | Conventional units | SI units |
|---|---|---|
| RBCs | 0–3/HPF | 0–3/HPF |
| WBCs | 0–8/HPF | 0–8/HPF |
| Casts | 0–2 hyaline/LPF | 0–2 hyaline/LPF |
| Epithelial cells | 0–5/HPF | 0–5/HPF |
Clinical use
These composite ranges apply only to examination preparation.1 Report patient results against the intervals your laboratory has verified for its methods and patient population. Under the Clinical Laboratory Improvement Amendments, laboratories verify or establish reference intervals before reporting patient results according to the test system's FDA clearance or approval and the available manufacturer performance specifications.2
Practice
References
- American Society for Clinical Pathology Board of Certification. Medical Laboratory Scientist, MLS(ASCP) and MLS(ASCPi) Examination Content Guideline. Revised June 9, 2026. pp 14–17. Accessed August 28, 2026. ASCP BOC examination content guideline. Back to text
- Code of Federal Regulations. 42 CFR § 493.1253(b)(1)(ii), (b)(2)(vi). Accessed August 28, 2026. Establishment and verification of performance specifications. Back to text