In Blood testing, exact measurement of results is necessary. The measurement in laboratory tests must be the same every time and in every place. Your physician must be able to rely on a known and accepted standard. Different units of measure are used depending on the substance being measured. Normally, in Blood laboratory testing the metric system is used to measure mass, volume, and length. Grams are the standard to express measurement of mass, the amount of matter in an object (similar to weight which is affected by gravity.) Liters are the standard to express measurement of volume, the amount of space that an object occupies. Meters are the standard to express measurement of length.
One great convenience of the metric is that it is based on multiples of 10. Another is that it is accepted universally around the world. This is the way that Blood is measured.
Prefixes, indicating which multiple of 10 is meant, can be attached to the basic unit, such as meter (m), liter (L), or gram (gm), to help make a number more readable and more easily understood. Commonly used prefixes include kilo (k), deci (d), centi (c), milli (m), and micro (µ).
Other units of measure communicate different measured properties of a substance. For example, a mole (mol) is the number of particles (molecules) in a substance. Regardless of the substance, 1 mole always expresses a number equivalent to the exact same number of particles. However, the number of grams in 1 mole may vary greatly from substance to substance. One mole equals the molecular (atomic) weight of a substance in grams. For example, the molecular weight of calcium is 40, and 1 mole of calcium equals 40 grams. Osmoles (Osm) and milliosmoles (mOsm) refer to the number of particles in a specific amount of liquid. Equivalents (Eq) and milliequivalents (mEq) measure a substance's ability to combine with another substance. A milliequivalent is roughly equivalent to a milliosmole.
Formulas are used to convert a measurement from one unit to another. The same amount can be expressed in terms of different units. For example, the concentration of calcium in the Blood is normally about 10 milligrams in a deciliter (mg/dL), 2.5 millimoles in a liter (mmol/L), or 5 milliequivalents in a liter (mEq/L).
In the United States, Blood laboratories use a different version of the metric system than does most of the rest of the world, which uses the Systeme Internationale (SI). In some cases translation between the two systems is simple. The difference between the two systems is most noticeable in the measurement of chemical concentration. The American system generally uses mass per unit volume, while the Systeme Internationale uses moles per unit volume. Since mass per mole varies with the molecular weight of the substance being analyzed, conversion between American and Systeme Internationale units requires many different conversion factors.
At BloodBook.com, a great many of our visitors are from outside of the United States. Therefore, where available and appropriate, "Systeme Internationale" (SI) units are provided following "American" units.
We have listed below the unit of measure abbreviations used on BloodBook.com.
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last updated 09/10/2005 bloodbook.com