Bicarbonate (HCO₃⁻) – Serum Test Overview Bicarbonate (HCO₃⁻) is a vital component of the body’s pH buffering system. It helps maintain the acid-base balance in the blood and other bodily fluids. Measuring serum bicarbonate provides valuable insight into a person’s metabolic and respiratory status. Purpose of the Test The serum bicarbonate test is used to: Evaluate acid-base balance in the body Monitor patients with kidney disease, lung disorders, or metabolic conditions Help diagnose conditions such as: Metabolic acidosis (low bicarbonate levels) Metabolic alkalosis (high bicarbonate levels) Respiratory acidosis/alkalosis Monitor the effectiveness of treatments for acid-base imbalances Sample Type Serum: Blood is drawn from a vein and allowed to clot, then the serum is separated for analysis. Normal Reference Range Typically: 22 to 29 mmol/L (Ranges may vary slightly depending on the laboratory) Causes of Abnormal Levels Low Bicarbonate (Metabolic Acidosis) Kidney disease (renal failure) Diabetic ketoacidosis Lactic acidosis Severe diarrhea Addison's disease High Bicarbonate (Metabolic Alkalosis) Prolonged vomiting or gastric suction Excessive antacid use Cushing's syndrome Chronic respiratory diseases (compensation for respiratory acidosis) Clinical Significance Abnormal serum bicarbonate levels may indicate underlying metabolic or respiratory disorders and are often interpreted along with other electrolyte and blood gas results (e.g., pH, PCO₂, and anion gap). Test Preparation No special preparation is usually needed. Inform your healthcare provider about medications, as diuretics and antacids can affect bicarbonate levels. Conclusion The serum bicarbonate test is an essential diagnostic tool for assessing the body's acid-base homeostasis. Regular monitoring may be needed for patients with chronic kidney or lung conditions, and those receiving treatments that can alter electrolyte balance.