Bicarbonate (HCO3) Lab Values

Objective:

Determine the significance and clinical use of Bicarbonate Lab Value in clinical practice

Lab Test Name:

Bicarbonate – HCO3–

Description:

This test measures the amount of bicarbonate, a form of carbon dioxide, in your blood. 

Bicarbonate, also known as HCO3, is a byproduct of your body’s metabolism. Your blood brings bicarbonate to your lungs, and then it is exhaled as carbon dioxide. Your kidneys also help regulate bicarbonate.

Bicarbonate is excreted and reabsorbed by your kidneys. This regulates your body’s pH, or acid balance. 

Bicarbonate also works with sodium, potassium, and chloride. These substances are called electrolytes; this is why these are often measured at the same time as bicarbonate.

Indications:

You may need this test to watch issues that affect pH levels in your blood. You may also have this test if you have kidney disease, liver failure, or other conditions related to metabolism.

• Metabolic acidosis-metabolic acidosis is diagnosed when the serum pH is reduced, and the serum bicarbonate concentration is abnormally low
• Metabolic alkalosis- when the serum pH is >7.45 and serum bicarbonate concentration is high.
• Kidney disease
• Liver failure
• Metabolic dysfunction

Normal Therapeutic Values:

Normal – 

• 23-30 mEq/L 
  • venous draw in electrolyte studies
  • Reported as CO2

Collection:

• Plasma separator tube

What would cause increased levels?

A high level of bicarbonate in your blood can be from metabolic alkalosis, a condition that causes a pH increase in tissue.

Metabolic alkalosis 

• COPD- lungs unable to compensate
• Excessive vomiting-loss of acid
• Loop/Thiazide diuretics- MOA of medications increases renal H+ loss
• Hypokalemia-H+(acid) shifts intracellularly, and causes increased renal hydrogen excretion
• Mineralocorticoid excess- 
  • Cushing’s Syndrome
  • Hyperaldosteronism

What would cause decreased levels?

A low level of bicarbonate in your blood may cause a condition called metabolic acidosis, or too much acid in the body.

Metabolic acidosis 

Loss of bicarbonate – diarrhea

Increased acid production or retention:

• Reduced renal acid excretion
  • Acute or chronic kidney disease
• Diabetic Ketoacidosis- alternate metabolism of fat produces ketones
• Lactic acidosis- related to sepsis, organ damage/failure, etc.