What is a CO2 Blood Test?

Carbon Dioxide, or CO2 for short, plays a vital role in our bodies. It does the following:

  • In the form of bicarbonates, they regulate the balance of pH in our blood
  • They also help relax blood vessels, which improves air and blood flow
  • They aid in oxygen distribution and metabolism
  • They regulate glucose uptake and antibody-antigen affinity
  • It helps to keep our breathing normal when exercising

While the presence of CO2 in our bodies can benefit us, having too much or too little of it can cause unwanted problems.

The CO2 Blood Test was developed to measure the level of Carbon Dioxide in our bodies by measuring bicarbonates (the form that Carbon Dioxide takes in our bodies until they’re exhaled).

It is usually conducted when a patient presents themselves with symptoms such as:

  • Weakness and fatigue
  • Difficulty breathing
  • Diarrhea
  • Nausea and vomiting
  • Confusion and disorientation

Phlebotomists conduct this test to determine if there is an electrolyte imbalance in the body and to determine the possibility of the patient having high blood pressure, lung problems, kidney problems, liver issues, and digestive issues.

The results of this test will help guide healthcare providers when determining what other tests to conduct and, throughout the diagnostic process, what treatment they should provide to patients.

View our free CO2 Blood Test

Download our free CO2 Blood Test PDF here

How to conduct a CO2 Blood Test

Blood Tests, in general, are some of the easiest medical procedures to conduct. Some of them require patients to fast for several hours before the test, but for CO2 Blood Tests, they don’t have to. They can eat and drink as usual, but they do need to inform healthcare professionals about any medications, vitamins, and supplements they take because these might affect the results.

On the day and time of the test, the phlebotomist or nurse conducting it will do the following:

  • They will have the patient sit down and have them outstretch one of their arms
  • Next, they will clean and disinfect the blood drawing site with antiseptic
  • After cleaning the site, they will tie a stretchy band above the drawing site. This makes the veins more visible
  • They will use a collection tube with a needle to draw a small amount of blood from the vein
  • After getting the amount of blood they need, they will remove the needle and apply a cotton ball or bandage on the drawing site to stop any bleeding that occurs. The patient might feel pain or discomfort (this will depend on their pain tolerance)
  • The phlebotomist or nurse will send the blood sample to a laboratory to be analyzed by a machine

How are the results of a CO2 Blood Test interpreted?

What counts as a normal range for CO2 levels will depend on the laboratory analyzing the blood sample, and they will also vary depending on the patient's age.

To give you a benchmark, we can follow the normal ranges established by the American Association of Clinical Chemistry:

  • For those aged 18 to 59: 23 - 29 mmol/l (millimoles per liter)
  • For those aged 60 to 89: 23 - 31 mmol/l
  • For those aged 90+: 20 - 29 mmol/l

If the results show that the patient has a CO2 level higher than the normal range, they might have the following problems:

  • Hormonal disorders
  • Respiratory acidosis
  • Metabolic alkalosis
  • Kidney problems
  • Lung problems
  • Cushing’s syndrome

If the results show that the patient has a CO2 level lower than the normal range, they might have the following problems:

  • Respiratory alkalosis
  • Metabolic acidosis
  • Addison’s disease
  • Kidney problems
  • Ketoacidosis (especially if the patient is diabetic)

Please note that CO2 Blood Tests are not meant to diagnose patients with conditions. They only point to the possibility of potential problems a patient might have. You can consider this blood test one of the preliminary tests to conduct as part of a comprehensive examination. It can help set the groundwork for the next set of tests.

CO2 Blood Test Example:

Healthcare providers who conduct blood tests usually have sheets where they record the results alongside the results of other tests.

If you don’t have a template for CO2 Blood Tests, we’d like you to know we have a free CO2 Blood Test PDF template you can download!

Our free CO2 Blood Test template is printable, but if your healthcare group or institution has gone paperless, you can use the PDF file because it has interactable fields! There are sections where you can do the following:

  • Indicate the CO2 levels of your patient (the template leaves room for you to indicate your laboratory’s normal ranges)
  • Tick checkboxes to indicate any symptoms of abnormal CO2 levels your patient might have
  • Write down notes in comment boxes (you can indicate your patient’s current health status and plans after receiving the blood test results

Here is what the PDF looks like:


If you like what you see and believe this is an excellent way to record patient information and CO2 Blood Test results, feel free to download our printable CO2 Blood Test PDF template!

Check out our free CO2 Blood Test PDF

CO2 Blood Test Example

When are CO2 Blood Tests conducted?

Here are examples of the times when CO2 Blood Tests are usually conducted:

If a patient has symptoms of abnormal CO2 levels

As mentioned earlier, CO2 Blood Tests are often discussed and conducted when a patient mentions they have symptoms such as weakness, fatigue, difficulty breathing, diarrhea, nausea, vomiting, confusion, and disorientation.

These are symptoms of abnormal CO2 levels in the body and other potential problems, so this test can help professionals determine what possible health issues the patient has based on the blood test results and symptoms.

Routine/mandatory check-ups

Some people schedule routine check-ups to update themselves about their current health status. They can request a CO2 Blood Test to check if they have potential problems related to abnormal CO2 levels in the body, and if they do or are at risk of specific health issues, they can immediately make the necessary lifestyle changes and take treatment to manage the problems early.

Some people might need to undergo this test as part of a mandatory annual physical examination required by their employers to check for any potential issues their employees are at risk for or have.

Check-ups for patient monitoring

If patients are confirmed to have abnormal CO2 levels and particular health issues related to CO2 level abnormalities (e.g., metabolic problems, kidney disorders, liver issues, respiratory conditions), healthcare providers can conduct CO2 Blood Tests to monitor patients occasionally. The results can help professionals tell if the patient is getting better and their treatments are working.

Are CO2 Blood Tests painful?
Are CO2 Blood Tests painful?

Commonly asked questions

Are CO2 Blood Tests painful?

There will be a little pain, depending on a person’s pain tolerance. Some might feel a bit of pain once the blood drawing needle pierces their skin, while some don’t. There might be discomfort after blood is drawn, and in some cases, the patient might feel lightheaded for a moment.

How long does it take for results to be processed?

It may take one to two days for the results to be processed and released.

What factors can affect CO2 Blood Test results?

Besides the symptoms mentioned earlier, dehydration can affect the results. Being dehydrated will increase the level of CO2 in the bloodstream.

How long does it take to conduct a CO2 Blood Test?

It should take between two to five minutes.

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