Blood tests are routine assessments that offer insights into various aspects of health. Carbon dioxide (CO2) levels in the blood frequently appear on reports like the basic metabolic panel (BMP) or comprehensive metabolic panel (CMP). This article explains what a low CO2 reading on blood work signifies, shedding light on its role in the body and potential implications for your health.
Understanding Blood Carbon Dioxide
When blood tests measure “carbon dioxide,” they primarily assess the amount of bicarbonate (HCO3-) in the bloodstream. Bicarbonate is a key electrolyte that helps regulate the body’s acid-base balance, known as pH. Maintaining a stable pH is important for various bodily functions.
The body produces carbon dioxide as a waste product when it breaks down food for energy. While the lungs expel some CO2, the kidneys filter the rest, and the blood carries most of it as bicarbonate. Normal adult blood CO2 levels, measured as bicarbonate, fall within a range of 23 to 29 millimoles per liter (mmol/L), though this can vary slightly between laboratories.
Common Reasons for Low Blood Carbon Dioxide
A low blood carbon dioxide level, often indicating metabolic acidosis, means there is too much acid in the body’s fluids. This imbalance can arise from the body producing excessive acid or the kidneys being unable to remove enough acid.
Common causes of low blood carbon dioxide include:
Diabetic ketoacidosis (DKA): Occurs when the body lacks sufficient insulin, leading to a buildup of acidic ketone bodies, primarily seen in uncontrolled type 1 diabetes.
Kidney disease: Conditions like chronic kidney disease (CKD) and acute kidney injury (AKI) impair the kidneys’ ability to remove acid from the blood.
Severe diarrhea: Leads to hyperchloremic acidosis as the body loses too much sodium bicarbonate.
Lactic acidosis: Stems from an accumulation of lactic acid, produced when the body breaks down carbohydrates for energy in low-oxygen conditions. Triggers include severe infection (sepsis), heart failure, liver failure, intense prolonged exercise, or certain medications like metformin or salicylates (aspirin).
Poisonings: Substances like aspirin, ethylene glycol (antifreeze), or methanol can induce metabolic acidosis.
Severe dehydration: Can disrupt the body’s acid balance.
Recognizing Symptoms and Seeking Care
Symptoms associated with low blood carbon dioxide vary depending on the underlying cause and the severity of the acid imbalance. In milder cases, or if acidosis develops slowly, individuals may not experience noticeable symptoms. However, as the condition progresses, more distinct signs can emerge.
Common symptoms include rapid and deep breathing, often described as “air hunger,” as the body attempts to compensate by expelling more carbon dioxide to raise blood pH. Other symptoms may include confusion, fatigue, nausea, vomiting, loss of appetite, and weakness. A fast heartbeat can also be observed. If these symptoms appear, particularly in combination, seeking medical attention is important, as untreated metabolic acidosis can worsen quickly and lead to serious complications.
How Low Carbon Dioxide is Addressed
Addressing low blood carbon dioxide primarily involves identifying and treating the underlying cause of the metabolic acidosis. Healthcare providers begin by conducting a physical examination and reviewing symptoms, then ordering additional diagnostic tests to pinpoint the source of the imbalance. These tests might include a complete electrolyte panel, blood glucose levels, kidney function tests, and sometimes an arterial blood gas (ABG) for a more precise measure of blood pH and gas levels.
Treatment strategies are tailored to the specific cause. For instance, in diabetic ketoacidosis, management involves fluid resuscitation to correct dehydration, insulin therapy to lower high blood sugar and ketones, and electrolyte replacement. For cases related to kidney disease, treatment may involve medications, dietary adjustments, or, in severe instances, dialysis. If medication toxicity or poisoning is the cause, specific antidotes or supportive care will be administered. Sodium bicarbonate may be given intravenously in cases of severe acidosis, but this is used selectively.