Evidence Based

Carbon Dioxide Poisoning & Causes of High CO2 in the Blood

Written by Mathew Eng, PharmD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
Medically reviewed by
Puya Yazdi, MD | Written by Mathew Eng, PharmD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Carbon Dioxide Poisoning

Carbon dioxide is a colorless, odorless gas. Recognizing poisoning can be challenging unless you know the symptoms. Find out what can increase your carbon dioxide levels to dangerous amounts and how to stay safe.

Carbon Dioxide Poisoning


Normally the concentration of CO2 in the air we breathe is very low (at around 0.04%) and harmless to the body. Even at much higher air concentrations, like 1%, it may only cause mild drowsiness in some people [1, 2].

However, at extremely high levels, greater than 10%, CO2 can cause convulsions, coma, and death. This happens because high concentrations of CO2 will displace the available oxygen, causing anyone nearby to suffocate [1, 2].

Carbon dioxide is a colorless, odorless gas, making it difficult to realize you are being exposed to dangerously high levels unless you can recognize the symptoms [1].

But cases of poisoning are fairly rare; less than 100 people die from CO2 poisoning each year in the U.S. [1, 2]

Also, make sure you don’t confuse carbon dioxide with carbon monoxide. Carbon monoxide (CO) poisoning is generally much deadlier and affects about 50,000 people each year in the U.S. [3].


The most common cause of CO2 poisoning is working in small, poorly ventilated spaces such as basements, storage tanks, and mines. Poisoning can also occur in areas where alcoholic beverages are made, like wineries, breweries, and cellars. This is because the fermentation process that produces alcohol also creates CO2 [1, 4].

A source of CO2 that is often overlooked is dry ice, which is the frozen form of CO2. There are a few reports of CO2 poisoning caused by dry ice melting in enclosed spaces [2, 5].

Volcanoes also emit CO2 in large quantities, which can collect into nearby pocketed locations. A small number of CO2 poisoning cases have been attributed to volcano emissions [6].

The most common cause of carbon dioxide poisoning is working in small, enclosed spaces without proper ventilation.

Causes of High Carbon Dioxide Levels

CO2 levels are closely tied to the pH of your blood. This is because most of the CO2 in your body is in the form of HCO3-, which plays an important role in maintaining blood pH [7, 8].

For this reason, disorders that alter the pH of the blood often have effects on CO2 levels as well. The normal range of blood pH in humans is 7.35 to 7.45. Conditions that cause blood pH to go outside of the normal range include [7, 8]:

  • Acidosis: occurs when blood pH becomes more acidic and pH drops below 7.35
  • Alkalosis: occurs when blood pH becomes more basic and pH rises above 7.45

These acid-base imbalances can further be classified as metabolic or respiratory [7, 8]:

  • Metabolic conditions are caused by changes in bicarbonate levels in the blood, mainly due to increased acid levels or kidney disorders
  • Respiratory conditions are caused by abnormal breathing rates, either by breathing too fast or too slow

In the following sections, we’ll discuss different acid-base disorders and other factors that lead to high CO2 levels.

Abnormal CO2 levels are usually caused by imbalances in the blood pH or breathing issues.

Metabolic Alkalosis

Metabolic alkalosis occurs when blood pH increases above 7.45, becoming too basic. This happens when the level of hydrogen ions decreases and/or when HCO3- becomes too high. Mild cases usually have no symptoms, but severe alkalosis can cause abnormal heart rhythms, confusion, and coma [9, 10].

Hydrogen ions (H+) are released when an acid, like carbonic acid, reacts with water. Hydrogen ions are also what is used to measure pH, so a drop in H+ will directly increase blood pH. Some common reasons for H+ loss include [9, 10]:

  • A shift of hydrogen ions into the cells
  • Dehydration
  • Vomiting
  • Medications, like diuretics that increase urination of hydrogen ions

Metabolic alkalosis can also occur when HCO3- levels become too high. Some ways that HCO3- can become elevated include [9, 10]:

  • Kidney issues that reduce the urination of HCO3-
  • Taking too many antacids

How does HCO3- increase CO2?

When HCO3- becomes too high, the body naturally compensates by slowing your breathing rate, causing a buildup of CO2 in the blood. The body does this because CO2 reacts with water molecules to form carbonic acid (H2CO3), which can help bring down the blood pH back to normal [9, 10].

During metabolic alkalosis, the body naturally slows your breathing rate which causes a buildup of CO2.

Respiratory Acidosis

Whenever you exhale, you are breathing out the CO2 that is produced by your metabolism. Conditions that slow or block your ability to breathe can cause a buildup of CO2 in your blood, which is referred to as respiratory acidosis or hypercapnia. This elevation of CO2 leads to greater amounts of carbonic acid, resulting in a decrease in blood pH and acidosis [11, 12].

Any condition that disrupts your ability to breathe can cause respiratory acidosis. Some common examples include [11, 12]:

  • Asthma
  • COPD
  • Pneumonia
  • Sleep apnea
  • Obesity

Symptoms of respiratory acidosis can vary depending on the underlying cause and may include [11, 12]:

Check out our article on respiratory acidosis for a complete breakdown of this condition.

Conditions like asthma or COPD can slow or partially block your ability to breathe, causing CO2 levels to rise.


Several drugs can cause an increase in CO2 levels. As mentioned earlier, diuretics like furosemide can disturb the balance of electrolytes in the body, leading to higher HCO3- and CO2 levels [13].

Taking an excessive amount of antacids containing calcium can cause calcium levels and blood pH to increase. Both of these factors can elevate HCO3- levels, leading to metabolic alkalosis and an increase in CO2 [9, 10].

Sodium bicarbonate, more commonly known as baking soda, is sometimes used in the hospital to treat certain conditions, like overdoses and high potassium levels (hyperkalemia). Sodium bicarbonate directly increases HCO3- levels, which can lead to alkalosis and elevated CO2 [9, 10].

Certain corticosteroids, such as dexamethasone and triamcinolone, can change how the kidneys reabsorb electrolytes, which also leads to higher HCO3- levels [14, 15].

Medications that may increase CO2 levels include diuretics, antacids containing calcium, sodium bicarbonate, and corticosteroids.

Environmental Factors

Since the start of the industrial revolution in the 18th century, global carbon dioxide levels have almost doubled. Today, certain areas in the world have very high CO2 levels in the air, due to several factors like pollution, deforestation, and emissions from burning fossil fuels [16].

One recent study of 13,000 cities across the world found that the cities with the highest CO2 emissions include Seoul, South Korea; Guangzhou, China; and New York City, U.S. The use of fossil fuels by vehicles and industrial plants plays a major role in CO2 levels in all of these cities [17].

Research shows that a combination of high CO2, pollution, and climate change has serious effects on human health, such as increasing the risk of lung disorders, infectious diseases, birth defects, and death in general [18, 19].

Living in cities with high CO2 levels in the air may cause a number of health issues and can increase your risk of dying.

Negative Health Effects of High CO2 Levels

So far we have discussed how high CO2 levels can alter the pH and oxygen balance in the blood, leading to negative health effects and symptoms. But research shows that chronically high CO2 levels may have additional harmful health consequences.

Cognitive Decline

As mentioned in the carbon dioxide poisoning section, very high concentrations of CO2 in the air can be toxic. However, emerging research suggests that long term exposure to slightly elevated levels of CO2 may also have negative effects on cognition and decision making.

The normal concentration of CO2 in the Earth’s atmosphere is about 0.04%. One study looked at the effects of exposure to CO2 concentrations at 0.06%, 0.1%, and 0.25% after three 2.5 hour sessions. The group exposed to 0.25% of CO2 in the air performed significantly worse on tests measuring decision-making compared to the groups exposed to lower CO2 levels [20].

Another study looked at 6 different CO2 concentrations, ranging from 0.05% to 0.14%. After 6 full workdays of exposure in an office environment, the group exposed to the highest CO2 levels performed the worst on cognition tests measuring activity, concentration, and strategic thinking [21].

Most importantly, these studies reveal that CO2 levels commonly seen in office buildings, which is usually about 0.09%, may hinder the performance and health of workers [20, 21].

Chronic exposure to elevated CO2 levels may worsen your cognition.

How to Reduce Carbon Dioxide Levels

Lifestyle Changes

If your CO2 levels are too high, the first step your doctor will take is treating the underlying condition that is causing the imbalance. This could mean anything from treating possible kidney or lung issues to stopping certain medications [8].

But there are some simple steps you can take yourself to help improve your CO2 levels.

For high CO2 levels:

  • Quit smoking, smokers are exposed to CO2 levels 350 times more than normal air [22]
  • Lose weight, obesity is a risk factor for breathing disorders like sleep apnea that increase CO2 levels [23]
  • Get some fresh air, exposure to nature has multiple benefits to physical and mental health. Even just leaving the office occasionally to go outside can lower CO2 levels [20, 24, 25]

Learn More

This post is part of a three-part series about carbon dioxide. Read the other parts to learn about:

Irregular CO2 Levels?

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High carbon dioxide levels in the blood are usually caused by imbalances in your blood pH or by conditions that affect your ability to breathe.

Living in cities with high CO2 emissions may also lead to higher CO2 levels. Research shows that chronic exposure to even slightly elevated CO2 levels may negatively affect cognition.

Although rare, exposure to extremely high CO2 levels can lead to carbon dioxide poisoning, which can be fatal. Carbon dioxide poisoning is usually caused by working in small enclosed spaces with no ventilation.

About the Author

Mathew Eng

Mathew received his PharmD from the University of Hawaii and an undergraduate degree in Biology from the University of Washington.
Mathew is a licensed pharmacist with clinical experience in oncology, infectious disease, and diabetes management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions.

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