Arterial Blood Gas Analysis – Indications, Procedures, Results

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 10 min read
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Arterial blood gas analysis; ABG; Hypoxia - ABG; Respiratory failure - ABG Blood gases are a measurement of how much oxygen and carbon dioxide are in your blood. They also determine the acidity (pH) of your blood. An arterial blood gas (ABG) test is a blood test that requires...

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Article Summary

Arterial blood gas analysis; ABG; Hypoxia - ABG; Respiratory failure - ABG Blood gases are a measurement of how much oxygen and carbon dioxide are in your blood. They also determine the acidity (pH) of your blood. An arterial blood gas (ABG) test is a blood test that requires a sample from an artery in your body to measure the levels of oxygen and carbon dioxide in your blood....

Key Takeaways

  • This article explains How the Test is Performed in simple medical language.
  • This article explains How to Prepare for the Test in simple medical language.
  • This article explains How the Test will Feel in simple medical language.
  • This article explains Why the Test is Performed in simple medical language.
Educational health guideWritten for patient understanding and clinical awareness.
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Use this article to understand possible causes, tests, treatment options, prevention, and questions to ask your clinician.

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Definition

Arterial blood gas analysis; ABG; Hypoxia – ABG; Respiratory failure – ABG

Blood gases are a measurement of how much oxygen and carbon dioxide are in your blood. They also determine the acidity (pH) of your blood.

An arterial blood gas (ABG) test is a blood test that requires a sample from an artery in your body to measure the levels of oxygen and carbon dioxide in your blood. The test also checks the balance of acids and bases, known as the pH balance, in your blood

How the Test is Performed

Usually, blood is taken from an artery. In some cases, blood from a vein may be used.

Blood may be collected from one of the following arteries:

  • Radial artery in the wrist
  • Femoral artery in the groin
  • Brachial artery in the arm

The health care provider may test circulation to the hand before taking a sample of blood from the wrist area.

The provider inserts a small needle through the skin into the artery. The sample is quickly sent to a laboratory for analysis.

How to Prepare for the Test

There is no special preparation. If you are on oxygen therapy, the oxygen concentration must remain constant for 20 minutes before the test.

Tell your provider if you are taking any blood-thinning medicines (anticoagulants), including aspirin.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

The test is used to evaluate respiratory diseases and conditions that affect the lungs. It helps determine the effectiveness of oxygen therapy. The test also provides information about the body’s acid/base balance, which can reveal important clues about lung and kidney function and the body’s general metabolic state .

Normal Results

Values at sea level:

  • Partial pressure of oxygen (PaO2): 75 to 100 mm Hg (10.5 to 13.5 kPa)
  • Partial pressure of carbon dioxide (PaCO2): 38 to 42 mm Hg (5.1 to 5.6 kPa)
  • Arterial blood pH: 7.38 to 7.42
  • Oxygen saturation (SaO2): 94% to 100%
  • Bicarbonate – (HCO3): 22 to 28 mEq/L

Note: mEq/L = milliequivalents per liter; mmHg = millimeters of mercury

At altitudes of 3,000 feet (900 meters) and higher, the oxygen value is lower.

Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may be due to lung, kidney, or metabolic diseases. Head or neck injuries or other injuries that affect breathing can also lead to abnormal results.

Risks

There is very little risk when the procedure is done correctly. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with this test may include:

  • Bleeding at the puncture site
  • Blood flow problems at puncture site (rare)
  • Bruising at the puncture site
  • Delayed bleeding at the puncture site
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

FAQ

What is the ABG test normal range?

  • The following are normal ranges for results of a blood gas test: pH: 7.35–7.45. partial pressure of oxygen (PaO2): 80–100 millimeters of mercury (mmHg) partial pressure of carbon dioxide: 35–45 mmHg.

Why is an arterial blood gas test done?

  • An arterial blood gases test is done to check for severe breathing and lung problems. The test also checks how well treatments for lung problems are working. And the test can look for changes in how well your lungs, heart, or kidneys are working.

What did the analysis of the patient’s arterial blood gases reveal?

  • Arterial blood gas analysis allows direct measurement of the quantity of carbon dioxide (PaCO2) and oxygen (PaO2) in the blood, results of which indicate how well the lungs are functioning.

What causes blood gases to be high?

  • Abnormal results on any part of a blood gases test may be an indication of disruption of normal breathing. They can also reflect problems in the body’s system of regulating its acid-base balance. Too much acid in the blood is known as acidosis, and too much base is called alkalosis.

What is an ABG why or when is it usually performed?

  • An arterial blood gas (ABG) test measures oxygen and carbon dioxide levels in your blood. It also measures your body’s acid-base (pH) level, which is usually in balance when you’re healthy. You may get this test if you’re in the hospital or if you have a serious injury or illness.

How do I get an ABG?

Continue to apply firm pressure to the puncture site for 3-5 minutes to reduce the risk of haematoma formation.

  1. Flush heparin through the needle.
  2. Insert the ABG needle.
  3. Advance the needle and observe for a flashback.
  4. Allow the syringe to self-fill.
  5. Remove the needle and apply immediate pressure.
  6. Engage needle safety device.

What is a normal ABG For a COPD patient?

  • Normal values are between 7.38 and 7.42. The acidity or alkalinity of the blood is linked with the amount of carbon dioxide in the blood. Acidic blood (pH less than 7.38) has high carbon dioxide levels in the blood.

What is the AVG test?

  • A blood gas test measures the amount of oxygen and carbon dioxide in the blood. It may also be used to determine the pH of the blood, or how acidic it is. The test is commonly known as a blood gas analysis or arterial blood gas (ABG) test. Your red blood cells transport oxygen and carbon dioxide throughout your body.

What are the two most important blood gases?

  • Oxygen (O2) and carbon dioxide (CO2) are the most important respiratory gases, and their partial pressures in arterial blood reflect the overall adequacy of gas exchange.

Who performs ABG?

  • For an arterial blood gas test, a respiratory therapist will take a sample of blood from one of your arteries. This is because there are higher oxygen levels in blood from an artery than blood from a vein. A respiratory therapist usually takes the sample from an artery inside your wrist known as the radial artery.

Can a nurse draw an ABG?

  • Most ABG samples can be drawn by a respiratory technician or specially trained nurse. Collection from the femoral artery, however, is usually performed by a doctor. Before attempting a radial puncture, you should perform Allen’s test.

Is an ABG test painful?

  • Arterial punctures for arterial blood gases (ABGs) analysis are described as the most painful laboratory procedure and are performed without the benefit of pain management.

What happens if your ABG is low?

Acid-base balance (pH).

  • If your blood acid level is out of balance, it can mean your body isn’t able to get rid carbon dioxide efficiently. This may happen because your lungs aren’t working well or your kidneys can’t get rid of the acid. A normal result is between 7.35 and 7.45.

What would ABGS look like in a client with COPD?

  • ABGs are near normal due to compensatory hyperventilation. The only subtle changes typically are a PaO2 slightly depressed (often in the mid-’70s, resulting in mild pulmonary vasoconstriction), and a low-normal PaCO2.

What is hypoxia in ABG?

  • Hypoxemia is defined as the partial pressure of oxygen in the arterial blood (PaO2) of less than 80 mm Hg, which is equivalent to a saturation of 95%.

What size needle is used for ABG?

  • Standard arterial blood gas kits typically contain 22- to 25-gauge needles. To assess whether smaller needles might decrease the pain of ABG draws, researchers conducted a randomized, controlled crossover trial in 50 healthy adult volunteers.Mar 6, 2015

Which arteries are best for ABGs?

  • During the blood draw, the healthcare provider will locate the radial artery in either the right or left arm. The radial artery is the preferred artery of choice because it is easier to locate and is superficial. Then a small needle is inserted into the artery and blood is withdrawn.

How do you tell if an ABG is acute or chronic?

  1. To determine whether it is acute or chronic. ΔH+ / ΔpaCO2 <0.3–chronic. >0.8–acute. 0.3-0.8–acute on chronic.
  2. Calculate compensation by the respective methods. Acute: [HCO3–] ↑ by 1 mEq/L for every 10 mmHg ↑ in paCO2 above 40. Chronic: [HCO3–] ↑ by 3.5 mEq/L for every 10 mmHg ↑ in paCO2 above 4.

How often should ABG be repeated?

  • Intermittent arterial blood gas analyses must be performed more frequently, up to every 10 minutes, to detect changes of 20% in arterial partial pressure of oxygen.

Why heparin is used for ABG?

  • Heparin prevents blood from clotting because the unique pentasaccharide sequence contained within its structure binds avidly to antithrombin III.

What color tube is used for ABG?

  • Red top tube with no additive. 4. Other no additive tubes. 5.

What is ABG ICU?

  • An arterial blood gas (ABG) analysis can tell you about a patient’s oxygenation, acid-base balance, pulmonary function, and metabolic status. This indispensable tool helps you assess and monitor critically ill patients in the ICU or other critical care settings.

Do ABGS need to be put on ice?

  • It is essential that the ABG sample be run within 10-15 minutes or immediately be put in a container of ice. An ABG sample can remain stable on ice for at least 1 hour.

What is the easiest way to learn ABGS?

Steps in ABG analysis using the tic-tac-toe method

  1. Memorize the normal values.
  2. Create your tic-tac-toe grid.
  3. Determine if pH is under NORMAL, ACIDOSIS, or ALKALOSIS.
  4. Determine if PaCO2 is under NORMAL, ACIDOSIS, or ALKALOSIS.
  5. Determine if HCO3 is under NORMAL, ACIDOSIS, or ALKALOSIS.

How do you know if ABG is metabolic or respiratory?

Having determined if the patient is acidotic or alkalotic, check the HCO3– and the PaCO2 to classify the results as follows:

  1. Metabolic acidosis: patients who are acidotic and have an HCO3– <22 (base excess <–2);
  2. Respiratory acidosis: patients who are acidotic with a PaCO2 >6;

How do you know if ABG is normal pH?

  1. Use pH to determine Acidosis or Alkalosis. ph. < 7.35. 7.35-7.45.
  2. Use PaCO2 to determine the respiratory effect. PaCO2. < 35.
  3. Assume metabolic cause when respiratory is ruled out. You’ll be right most of the time if you remember this simple table: High pH.
  4. Use HC03 to verify the metabolic effect. Normal HCO3- is 22-26.

What is an ABG girl?

  • The ABG is a stereotype that applies to Asian-American girls, or more broadly, Asian girls who have grown up in Western countries. The standard ABG has dyed her hair some color of balayage, usually blonde, sports false eyelashes on the daily, and likes to wear bodycon clothing.

How often do you check ABGS in ICU?

  • –7 In our ICU, ABG tests are performed once in the morning and at fixed intervals, for example, 4th hourly, 6th hourly at the doctor’s discretion, irrespective of the patient’s condition at that time.

Who tests ABG?

  • For an arterial blood gas test, a respiratory therapist will take a sample of blood from one of your arteries. This is because there are higher oxygen levels in blood from an artery than blood from a vein. A respiratory therapist usually takes the sample from an artery inside your wrist known as the radial artery.

How do you send an ABG sample?

  • Insert the needle just under the skin at a 60-90º angle, aiming in the direction of the artery, while palpating the femoral pulse proximal to the puncture site with the nondominant hand (see the image below). Insertion of the needle at the femoral artery puncture site. Advance the needle slowly.

Can a nurse draw an ABG?’

  • Most ABG samples can be drawn by a respiratory technician or a specially trained nurse. Collection from the femoral artery, however, is usually performed by a doctor. Before attempting a radial puncture, you should perform Allen’s test.

Why ABG analysis is important?

  • An arterial blood gas analysis (ABG) measures the balance of oxygen and carbon dioxide in your blood to see how well your lungs are working. It also measures the acid-base balance in the blood. Your kidneys and lungs keep this acid-base balance. You need this for the enzyme systems in your body to work at their best.

What is a normal ABG For a COPD patient?

  • Normal values are between 7.38 and 7.42. The acidity or alkalinity of the blood is linked with the amount of carbon dioxide in the blood. Acidic blood (pH less than 7.38) has high carbon dioxide levels in the blood.

What is an ABG why or when is it usually performed?

  • An arterial blood gas (ABG) test measures oxygen and carbon dioxide levels in your blood. It also measures your body’s acid-base (pH) level, which is usually in balance when you’re healthy. You may get this test if you’re in the hospital or if you have a serious injury or illness.

How does an ABG dress?

  • ABG is an acronym for an “aznbbygirl” meaning an Asian female gangster or babe. ABGs typically like to hang with Asian gangsters, wear sexy clothing, drink Henny (Hennessy), dye their hair blonde, and carry designer handbags. ABGs are also known for hanging in cliques and looking similar to one another.
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Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
  • Bring old prescriptions, investigation reports, and current medicines.
  • Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
  • Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

  • What is the most likely cause of my symptoms?
  • Which danger signs mean I should go to hospital quickly?
  • Which tests are necessary now, and which can wait?
  • How should I take medicines safely and what side effects should I watch for?
  • When should I come for follow-up?

Tests to discuss

  • Vital signs: temperature, pulse, blood pressure, oxygen saturation
  • Basic physical examination by a clinician
  • CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

  • Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
  • Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
  • Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

  • Avoid heavy lifting, sudden bending, and prolonged bed rest.
  • Use comfortable posture and gentle movement as tolerated.
  • Discuss physiotherapy, X-ray, or MRI only when clinically needed.

OTC medicine safety

  • For mild back pain, pain-relief medicine may be discussed with a doctor or pharmacist.
  • Avoid repeated painkiller use if you have kidney disease, stomach ulcer, uncontrolled blood pressure, or are taking blood thinners.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
  • Do not use steroid tablets or injections casually for quick relief.
  • Do not delay emergency care because of home remedies.

Get urgent help if

  • Back pain with leg weakness, numbness around private area, loss of urine/stool control, fever, cancer history, or major injury needs urgent care.
Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

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Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider
Tests to discuss with doctor
  • Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
  • Relevant blood, urine, imaging, or specialist tests only after clinical assessment
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Safe pathway to proper treatment

Care roadmap for: Arterial Blood Gas Analysis – Indications, Procedures, Results

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

RX Patient Help

Ask a health question safely

Write your symptom story. A health professional or site editor can review it before any answer is prepared. This box is not for emergency care.

Emergency first: Severe chest pain, breathing trouble, unconsciousness, stroke signs, severe injury, heavy bleeding, or rapidly worsening symptoms need urgent local medical care now.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area from the RX Article Professional Blocks panel.

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