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.