December 7, 2023
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Blood Test Health Medical Symptoms

Why CO2 blood test Is Necessary?


A CO2 blood test is a test that indicates whether your body is maintaining electrolytes. This test is also known as the bicarbonate test, total CO2 test, or HCO3 test. The recommended range of CO2 levels occurs between 20 to 29 millimoles per liter (mmol/L) and may lead to more complicated problems, such as lung or kidney disease. In this article, you will know when and why a carbon dioxide blood test is needed. 

What is the carbon dioxide blood test?

A carbon dioxide blood test helps your provider to determine the amount of bicarbonate. Bicarbonate gives the overall signals of the CO2 levels in the blood. 

Carbon dioxide is a waste chemical substance in your body. Your body includes two types of CO2, namely HCO3 (bicarbonate) and PCO2 (carbon dioxide). CO2 transports through your blood to the lungs. When you breathe, the CO2 comes from your lungs and releases from your body. Having a high or low amount of CO2 in your blood may lead to specific medical problems.


Why do you need to take a carbon dioxide blood test?

A CO2 blood test is often included in an electrolyte panel, which is a blood test. A healthcare provider may use this test to see any disorders between the oxygen and carbon dioxide in your blood or the pH imbalance. These disorders are associated with kidney, metabolic disorders, or other diseases. You may need to place an order for a CO2 blood test if you experience the following symptoms:

Breathing difficulty

  • Nausea and vomiting
  • Breathing difficulty
  • Fatigue or tiredness
  • Weakness

The mentioned symptoms may indicate problems in the function of the lungs that involve the interchange of oxygen and carbon dioxide. 

Request an online CO2 blood test to check your levels if you see these symptoms. 

What are the preparations required for a carbon dioxide blood test?

You can inform your healthcare provider before taking a CO2 blood test about medications, supplements, or vitamins. A few medications, such as antacids or corticosteroids, may influence the test result by increasing the amount of bicarbonate in your body. You may ask your healthcare provider about when to stop taking medications. 

This test does not require you to fast (avoiding drinking or eating). You may need fasting when a healthcare provider orders other blood tests with a CO2 blood test. 

Procedure for the CO2 blood test

Before visiting the laboratory, you can schedule an online CO2 blood test.

Procedure for CO2 blood test

The procedure involves the following:

  • You will need to sit in front of the healthcare provider. 
  • Remove the part of your cloth from the vein of one of your arms
  • A healthcare provider will inject a needle into your vein
  • The test tube that attaches to the needle will store your blood
  • A bandage will apply to your injected area. 
  • Your blood sample will be stored at the laboratory for examination
  • The complete procedure takes at least five minutes. 
  • The test results will be received within one to two days. 

What are the risks involved in this test?

These are the risks linked with the CO2 blood test. Here are the common minimal risk factors that include:

  • Lightheadedness
  • Infection at the injected site
  • Bleeding
  • Fainting
  • Hematoma (a condition of deposition of blood within your skin)

You may have a slight feeling of pain or sensation during blood injection. Discuss with your healthcare provider if you see these risks in the recent blood test. 

What does the CO2 blood test result indicate?

The test results may vary slightly among laboratories. It is because labs may use different methods for measurements. The normal level for CO2 lies between 23 to 29 mEq/L (milliequivalent units per liter of blood). Mostly, the blood test helps to show blood pH with CO2 levels to see the cause of your symptoms. Blood pH is a good indicator of showing acidity or alkalinity. When your fluids are alkaline in nature, it is known as alkalosis, while when your body fluids are acidic, it is called acidosis. 

What does the CO2 blood test result indicate

Normally, when your blood has a value of 7.4, it shows a slight basic nature. The pH value lies between 7.35 to 7.45 is neutral, while pH levels lesser than 7.35 are acidic. 

Causes of high CO2 in the blood

The presence of high CO2 in the blood and low pH (below 7.35) is a disorder known as respiratory acidosis. These are the common causes include:

  • Asthma
  • Lung cancer
  • Medications or drugs that lead to difficulty breathing, specifically when occurring with alcohol
  • Pneumonia (an infection of one or both of the lungs developed due to bacteria, fungi, or viruses)
  • Pulmonary fibrosis (a lung disease that develops when damage occurs in lung tissue)
  • Contact with hazardous substances or chemicals
  • Chronic obstructive pulmonary disease (COPD)
  • Obesity
  • Tuberculosis (a condition that develops due to germs that spread from one person to another via air)

A high CO2 in blood with high pH (above 7.45) is a disorder known as metabolic alkalosis. A few of the common reasons include:

  • Long-term vomiting
  • Low amount of potassium levels in the blood
  • Decreased breathing and CO2 (hypoventilation)

Causes of low CO2 in the blood

If you have low CO2 in your blood with low pH (below 7.35), known as metabolic acidosis. Following are the common causes include:

  • Kidney disease
  • Cancer
  • Long-term less supply of oxygen due to anemia, shock, or heart failure
  • Severe diarrhea
  • Seizures
  • Lactic acidosis
  • Diabetic ketoacidosis (A condition develop when you have a high acid amount in the blood, which occurs due to low insulin levels)

If the test results show low carbon dioxide in blood with high pH (above 7.5), it is known as respiratory alkalosis. These are the common causes include:

  • Fever
  • Hyperventilation 
  • Pain
  • Anxiety

How to decrease or increase the CO2 in the blood?

Increase CO2 in the blood:

A healthcare provider may recommend specific treatments to increase CO2 in the blood. You can add fruits and vegetables and take less meat, cheese, eggs, and grain. Speak with a healthcare provider to discuss the suitable methods to level the CO2 in the blood. 

Decrease CO2 in the blood:

If you experience a condition such as COPD, oxygen therapy can help to balance carbon dioxide levels in the blood. If the CO2 levels are higher than recommended, consult with a provider to receive the appropriate treatment.


A healthcare provider will observe a CO2 imbalance in your body by bicarbonate test. If your test results show very high or low CO2 in your blood, this may lead to a wide range of disorders. The treatment may depend on the causes of the abnormal CO2 levels. Your provider will suggest treatment based on your current medical condition. You may consult an online healthcare provider if you see the symptoms.

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