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SI (le Systéme International d’Unités) units are used in many countries to express clinical laboratory and serum drug concentration data.* Instead of using units of mass (eg, micrograms), the SI system uses moles (mol) to represent the amount of a substance. A molar solution contains 1 mole (the molecular weight of the substance in grams) of the solute in 1 L of solution. The following formula is used to convert units of mass to moles (mcg/mL to μmol/L or, by substitution of terms, mg/mL to mmol/L or ng/mL to nmol/L).
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An equivalent weight of a substance is the weight that will combine with or replace 1 g of hydrogen; a milliequivalent is 1/1000 of an equivalent weight.
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Milliequivalents per Liter
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