A CO2 blood test measures the amount of carbon dioxide in your blood, primarily assessing bicarbonate, its main form. Bicarbonate, an electrolyte, helps regulate the body’s fluid and acid-base (pH) balance. An imbalance in these levels can indicate underlying health issues.
What is the CO2 Blood Test?
The CO2 blood test measures total carbon dioxide content, with bicarbonate (HCO3-) accounting for 90% to 95% of this total. Bicarbonate acts as a buffer, neutralizing acids and maintaining blood pH. This test is frequently included in a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP).
Doctors order a CO2 blood test to evaluate kidney and lung function, as these organs regulate CO2 and bicarbonate levels. It helps diagnose or monitor conditions affecting the body’s acid-base balance, such as metabolic acidosis or alkalosis. The kidneys maintain normal bicarbonate levels, while the lungs regulate CO2 exhalation.
Decoding a Low CO2 Result
A low CO2 level, specifically low bicarbonate, indicates the body has too much acid or not enough bicarbonate to neutralize it. This condition is known as metabolic acidosis. Maintaining proper pH balance is important because it affects enzyme function, cellular processes, oxygen delivery, and breathing regulation.
Normal CO2 ranges typically fall between 23 to 30 mEq/L (or mmol/L) for adults, though these can vary slightly between laboratories. A reading below this range signals a low CO2 level.
Key Reasons for Low CO2
Several conditions can lead to low CO2 levels, primarily by causing acid accumulation or bicarbonate loss. Diabetic ketoacidosis (DKA), a common cause, occurs when uncontrolled diabetes leads to a buildup of acidic ketone bodies. The body compensates by increasing breathing to expel more CO2.
Kidney disease can also result in low CO2; healthy kidneys remove waste and acids from the blood, and impaired function can lead to acid accumulation. Additionally, significant fluid loss, such as from severe diarrhea, can lead to bicarbonate loss from the digestive tract, lowering blood CO2 levels.
Lactic acidosis involves increased lactic acid production, occurring due to conditions like severe infection (sepsis), shock, or intense exercise when oxygen levels are low. Certain medications can also affect CO2 levels, such as metformin (for diabetes) and aspirin overdose (salicylate poisoning), which alter the body’s acid-base balance.
While hyperventilation (rapid breathing) can initially lower CO2 by exhaling more carbon dioxide, a persistently low bicarbonate level usually points to metabolic acidosis. Addison’s disease, affecting the adrenal glands, can also lead to electrolyte imbalances that make the blood more acidic.
Recognizing Symptoms and Seeking Help
Symptoms of low CO2 levels often reflect underlying metabolic acidosis, including rapid, deep breathing—the body’s attempt to compensate for increased acidity. Other common symptoms include nausea, vomiting, abdominal pain, fatigue, weakness, confusion, headaches, or decreased appetite. Symptom severity varies widely depending on the cause and CO2 levels.
If you receive a low CO2 result or experience symptoms like persistent fatigue, trouble breathing, or confusion, consult a healthcare provider. Severe or worsening symptoms warrant prompt medical attention.
Approaches to Managing Low CO2
Managing low CO2 levels primarily involves addressing the underlying cause of metabolic acidosis. For diabetic ketoacidosis, controlling blood sugar with insulin and fluids is important. If kidney disease is the cause, treatment focuses on managing the condition, including medications or dietary changes.
Replenishing lost electrolytes and fluids, often via intravenous (IV) fluids, helps restore balance. In severe acidosis, sodium bicarbonate might be administered intravenously to neutralize excess acid. Review and adjust any contributing medications. Personalized treatment plans require working closely with a healthcare provider for accurate diagnosis and effective management.