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Information on the Anion Gap can be found on the Common Questions tab.
The Test Sample
What is being tested?
Electrolytes are minerals that are found in body tissues and blood in the form of dissolved salts. As electrically charged particles, electrolytes help move nutrients into and wastes out of the body's cells, maintain a healthy water balance, and help stabilize the body's acid/base (pH) level.
The electrolyte panel measures the blood levels of the main electrolytes in the body: sodium (Na+), potassium (K+), chloride (Cl-), and bicarbonate (HCO3-; sometimes reported as total CO2).
A person's diet provides sodium, potassium, and chloride. The kidneys help maintain proper levels by reabsorption or by elimination into the urine. The lungs provide oxygen and regulate CO2. The CO2 is produced by the body and is in balance with bicarbonate. The overall balance of these chemicals is an indication of the functional well-being of several basic body functions. They are important in maintaining a wide range of body functions, including cardiac and skeletal muscle contraction and nerve impulse conduction.
Any disease or condition that affects the amount of fluid in the body, such as dehydration, or affects the lungs, kidneys, metabolism, or breathing has the potential to cause a fluid, electrolyte, or pH imbalance (acidosis or alkalosis). Normal pH must be maintained within a narrow range of 7.35-7.45 and electrolytes must be in balance to ensure the proper functioning of metabolic processes and the delivery of the right amount of oxygen to tissues. (For more on this, see the condition article on Acidosis and Alkalosis and also on Dehydration.)
A related "test" is the anion gap, which is a value calculated using the results of an electrolyte panel. It reflects the difference between the positively charged ions (called cations) and the negatively charged ions (called anions). An abnormal anion gap is non-specific but can suggest certain kinds of metabolic or respiratory disorders or the presence of toxic substances. For more information on anion gap, see Common Questions #1.
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.