Serum Electrolytes Laboratory Test

Serum Electrolytes:
Electrolytes are substances that become ions in solution and acquire the capacity to conduct electricity. Electrolytes are present in the human body, and the balance of the electrolytes in our bodies is essential for normal function of our cells and our organs. These ions are measured to assess renal (kidney), endocrine (glandular), and acid-base function, and are components of both renal function and comprehensive metabolic biochemistry profiles. Their importance lies in part with the serious consequences that follow from the relatively small changes that diseases or abnormal conditions may cause.

Common electrolytes that are measured by doctors with blood testing include sodium, potassium, chloride, and bicarbonate. The functions and normal range values for these electrolytes are described below.

Specimen: venous blood
Pretest/Intratest/Post-test- same
Commonly ordered:
Sodium- 135-145 mEq/L
Potassium- 3.5-5.0 mEq/L
Chloride- 95-105 mEq/L

Sodium (Na+)
Sodium is primarily responsible for maintaining osmotic pressure. It maintains intracellular and extracellular fluid levels in the body. An increased serum sodium is present in states of dehydration as a result of diarrhea or vomiting. Low sodium levels usually are a result of too much water in the body.
Potassium (K+)
Potassium is a major component in cardiac function. Even small changes in Potassium can cause abnormal cardiac arrhythmias, affecting cardiac function. Too much potassium in the blood is usually caused by poor kidney function and can cause abnormal and sometimes fatal abnormalities in the heart rhythm. Low potassium levels are usually the result of potassium loss from excessive urination or from vomiting. A potassium level that is too low can cause abnormal heart rhythms.
Chloride (Cl-)
In combination with sodium, chloride maintains fluid levels by regulating osmotic pressure in the blood. An elevated chloride usually results from abnormal kidney function. A chloride level below normal usually results from excessive vomiting or diarrhea.