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All laboratory appendices should be interpreted with caution since normal values differ widely among clinical laboratories. The values given in this Appendix are meant primarily for use with this text. In preparing the Appendix, the editors have taken into account the fact that the system of international units (SI, syst_me international d’unités) is now used in most countries and in most medical and scientific journals.1 However, clinical laboratories in many countries continue to report values in traditional units. Therefore, both systems are used in the Appendix. Values in SI units appear first, and traditional units appear in parentheses after the SI units. The dual system is also used in the text except for (1) those instances in which the numbers remain the same but only the terminology is changed (mmol/L for meq/L or IU/L for mIU/mL), when only the SI units are given; and (2) most pressure measurements (e.g., blood and cerebrospinal fluid pressures), when the traditional units (mmHg, mmH2O) are used. In all other instances in the text the SI unit is followed by the traditional unit in parentheses. The SI base units, SI derived units, other units of measure referred to in Appendix, and SI prefixes are listed in Tables A-1 to A-3 at the end of Appendix. Conversions from one system to another can be made as follows:


1Young DS: Implementation of SI units for clinical laboratory data. Ann Intern Med 106:114,1987.

  • Body fluid, total volume: 50 percent (in obese) to 70 percent (lean) of body weight

    • Intracellular: 0.3–0.4 of body weight

    • Extracellular: 0.2–0.3 of body weight

  • Blood

    • Total volume:

      • Males: 69 mL per kg body weight

      • Females: 65 mL per kg body weight

    • Plasma volume:

      • Males: 39 mL per kg body weight

      • Females: 40 mL per kg body weight

    • Red blood cell volume:

      • Males: 30 mL per kg body weight (1.15–1.21 L/m2 of body surface area)

      • Females: 25 mL per kg body weight (0.95–1.00 L/m2 of body surface area)

2 Since cerebrospinal fluid concentrations are equilibrium values, measurements of the same parameters in blood plasma obtained at the same time are recommended. However, there is a time lag in attainment of equilibrium, and cerebrospinal levels of plasma constituents that can fluctuate rapidly (such as plasma glucose) may not achieve stable values until after a significant lag phase.

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Conversion Factor (CF) C × CF = SI
Osmolarity292–297 mmol/kg water (292–297 mOsm/L)
Sodium137–145 mmol/L (137–145 meq/L)
Potassium2.7–3.9 mmol/L (2.7–3.9 meq/L)
Calcium1.0–1.5 mmol/L (2.1–3.0 meq/L)0.5
Magnesium1.0–1.2 mmol/L (2.0–2.5 meq/L)0.5
Chloride116–122 mmol/L (116–122 meq/L)
CO2 content20–24 mmol/L (20–24 meq/L)
Pco26–7 kPa (45–49 mmHg)0.1333
Glucose2.2–3.9 mmol/L (40–70 mg/dL0.05551
Lactate1–2 mmol/L (10–20 mg/dL)0.1110
Total protein:0.2–0.5 g/L (20–50 mg/dL)0.01
Albumin0.066–0.442 g/L (6.6–44.2 mg/dL)0.01
IgG0.009 –0.057 g/L (0.9–5.7 mg/dL)0.01

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