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This test measures the amount of oxygen and carbon dioxide in your blood. It also checks the acidity of your blood. This is called your acid-base balance or your pH level. The blood sample is taken from an artery, which is a blood vessel that carries oxygen-rich blood from your lungs to your body.

In an ABG test, the blood oxygen measurement shows how well your lungs move oxygen from the air into your blood when you breath in. The carbon dioxide measurement shows and how well your lungs remove carbon dioxide from your blood when you breath out.

Carbon dioxide is an acidic waste product that your body makes. If your blood and tissues become even slightly too acidic or too basic (alkaline), it can seriously affect many of your organs and even become life-threatening.

Your lungs and your kidneys do much of the work to keep your acid-base balance normal. So, the acid-base measurement from an ABG test can help diagnose and monitor conditions that affect your lungs and kidnesys as well as many other conditions that may upset your acid-base balance.

Other names: blood gas test, arterial blood gases, ABG, , oxygen saturation test

What is it used for?

An ABG test is used to help:

Check your acid-base balance

Diagnose serious problems with your lungs and breathing

Diagnose kidney disorders

Find out whether treatment is working for breathing disorders, kidney disease, or other conditions that may affect your acid-base balance

Why do I need an arterial blood gas (ABG) test?

There are many reasons why you may need this test. For example, you may need an ABG test if you:

Have symptoms of a problem with your acid-base balance, such as:

Uncontrolled rapid or deep breathing, which may be a sign that your lungs are trying to adjust acids or bases by changing the amount of oxygen or carbon dioxide in your blood

Nausea and vomiting

Arrhythmia(a problem with the rate or rhythm of your heartbeat)

Confusion

Fatigue

Muscle twitching and/or cramps

Are being treated for a lung disease or a condition that affects your breathing, such as:

Asthma

Chronic obstructive pulmonary disease (COPD)

Cystic fibrosis

Myasthenia gravis

Have symptoms after you have had:

Carbon monoxide poisoning

An inhalation injury(breathing in smoke, hot air, and/or harmful chemicals)

A recent heador neck injury that could affect your breathing

Are receiving oxygen therapyin the hospital

What happens during a blood oxygen level test?

Most blood tests take a sample from a vein. For this test, a health care provider will take a sample of blood from an artery. That’s because blood from an artery has higher oxygen levels than blood from a vein.

The sample is usually taken from an artery on the inside of your wrist, but it may be taken from an artery in your arm or groin. For a newborn, the sample may be taken from the baby’s heel or the umbilical cord shortly after birth.

If your blood sample is taken from your wrist, the provider will first test your blood circulation. The provider will hold your wrist and apply pressure to the arteries to cut off blood flow to your hand for several seconds. Then the provider will let go of your wrist to check how quickly blood flow returns to your hand. If your blood flow is normal, the provider will collect a blood sample.

A blood sample taken from an artery tends to be more uncomfortable than most blood tests, which use a vein. So, the provider may apply some numbing medicine to your skin first. The provider will insert a needle with a syringe into the artery to remove some blood.

When the syringe is full, the provider will bandage the puncture site. Pressure will be applied to the site for at least 5 minutes to stop the bleeding.

Will I need to do anything to prepare for the test?

If you take blood thinners, including aspirin, ask your health care provider whether you should stop taking them before your test. And tell your provider about all other medicines and supplements you take. But don’t stop taking any medicines unless your provider tells you to.

If you are on oxygen therapy, your oxygen may be turned off for about 20 minutes before the test. This will be done only if you can breathe without oxygen therapy.

What do the results mean?

ABG test results involve many body systems that affect each other. And there are many health conditions that can cause abnormal results. For these reasons, it’s best to have your provider explain what your results mean for your health.

Your ABG test results will list many measurements, including:

Oxygen saturation (O2Sat).This measures how much oxygen your red blood cells are carrying

Partial pressure of oxygen (PaO2).This measures the pressure of oxygen that’s dissolved in your blood. It helps show how well oxygen moves from your lungs to your bloodstream.

Partial pressure of carbon dioxide (PaCO2).This measures the amount of carbon dioxide in your blood. It also shows how easily carbon dioxide can move out of your body.

Acid-base balance (pH level).This measures the acidity of your blood. Too much acid is called acidosis. Too much base (alkaline) is called alkalosis. These conditions are symptoms of other problems that upset the acid-base balance in your body.

An ABG test alone usually can’t provide a final diagnosis. So, if your results are not normal, your provider will likely order more tests to make a diagnosis. In general, abnormal results may mean you have a problem with your lungs or kidneys or a metabolic disorder. Metabolic disorders affect how your body uses food for energy. Certain medicines may also upset your acid-base balance and lead to abnormal ABG test results.

Is there anything else I need to know about blood oxygen level tests?

Another type of test, called pulse oximetry, can check your blood oxygen saturation levels. A small clip-like device, called a pulse oximeter, is usually attached to your finger. The device tells you the percentage of red blood cells that are full of oxygen. Pulse oximetry may be useful if blood oxygen levels are the only concern. Ask your provider if this test is right for you.

This test measures how long it takes for a clot to form in a blood sample. An INR (international normalized ratio) is a type of calculation based on PT (Prothrombin Time) test results.

Prothrombin is a protein made by the liver. It is one of several substances known as clotting (coagulation) factors. When you get a cut or other injury that causes bleeding, your clotting factors work together to form a blood clot. How fast your blood clots depends on the amount of clotting factors in your blood and whether they’re working correctly. If your blood clots too slowly, you may bleed too much after an injury. If your blood clots too fast, dangerous clots may form in your arteries or veins.

A PT/INR test helps diagnose the cause of bleeding or clotting disorders. It also checks to see if a medicine that prevents blood clots is working the way it should.

Other names: prothrombin time/international normalized ratio, PT protime

What is it used for?

A PT/INR test is most often used to:

See how well warfarin is working. Warfarin is a blood-thinning medicinethat’s used to treat and prevent dangerous blood clots. (Coumadin is a common brand name for warfarin.)

Find out the reason for abnormal blood clots

Find out the reason for unusual bleeding

Check clotting function before surgery

Check for liver problems

A PT/INR test is often done along with a partial thromboplastin time (PTT) test. A PTT test also checks for clotting problems.

Why do I need a PT/INR test?

You may need this test if you are taking warfarin on a regular basis. The test helps make sure you are taking the right dose.

If you are not taking warfarin, you may need this test if you have symptoms of a bleeding or clotting disorder.

Symptoms of a bleeding disorder include:

Unexplained heavy bleeding

Bruising easily

Unusually heavy nose bleeds

Unusually heavy menstrual periods in women

Symptoms of a clotting disorder include:

Leg pain or tenderness

Leg swelling

Redness or red streaks on the legs

Trouble breathing

Cough

Chest pain

Rapid heartbeat

In addition, you may need a PT/INR test if you are scheduled for surgery. It helps make sure your blood is clotting normally, so you won’t lose too much blood during the procedure.

What happens during a PT/INR test?

The test may be done on a blood sample from a vein or a fingertip.

For a blood sample from a vein:

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

What do the results mean?

If you were tested because you are taking warfarin, your results will probably be in the form of INR levels. INR levels are often used because they make it easier to compare results from different labs and different test methods. If you are not taking warfarin, your results may be in the form of INR levels or the number of seconds it takes for your blood sample to clot (prothrombin time).

If you are taking warfarin:

• INR levels that are too low may mean you are at risk for dangerous blood clots.
• INR levels that are too high may mean you are at risk for dangerous bleeding.

Your health care provider will probably change your dose of warfarin to reduce these risks.

If you are not taking warfarin and your INR or prothrombin time results were not normal, it may mean one of the following conditions:

A bleeding disorder, a condition in which the body can’t clot blood properly, causing excessive bleeding

A clotting disorder, a condition in which the body forms excessive clots in arteries or veins

Liver disease

Vitamin K Vitamin K plays an important role in blood clotting.

Is there anything else I need to know about a PT/INR test?

Sometimes certain liver tests are ordered along with a PT/INR test. These include:

Aspartate Aminotransferase (AST)

Alanine Aminotransferase (ALT)

This measures the level of c-reactive protein (CRP) in a sample of your blood. CRP is a protein that your liver makes. Normally, you have low levels of c-reactive protein in your blood. In cases of Inflammation, your liver releases more CRP into your bloodstream. High levels of CRP may mean you have a serious health condition that causes inflammation.

Inflammation is your body’s way of protecting your tissues and helping them heal from an injury, infection, or other disease. Inflammation can be acute (sudden) and temporary. This type of inflammation is usually helpful. For example, if you cut your skin, it may turn red, swell, and hurt for a few days. Those are signs of inflammation. Inflammation can also happen inside your body.

If inflammation lasts too long, it can damage healthy tissues. This is called chronic (long-term) inflammation. Chronic infections, certain autoimmune disorders, and other diseases can cause harmful chronic inflammation. Chronic inflammation can also happen if your tissues are repeatedly injured or irritated, for example from smoking or chemicals in the environment.

A CRP test can show whether you have inflammation in your body and how much. But the test can’t show what’s causing the inflammation or which part of your body is inflamed.

Other names: c-reactive protein, serum

What is it used for?

A CRP test may be used to help find or monitor inflammation in acute or chronic conditions, including:

Infections from bacteria or viruses

Inflammatory bowel disease, disorders of the intestines that include Crohn’s disease and ulcerative colitis

Autoimmune disorders, such as lupus, rheumatoid arthritis, and vasculitis

Lung diseases, such as asthma

Your health care provider may use a CRP test to see if treatments for chronic inflammation are working or to make treatment decisions if you have sepsis. Sepsis is your body’s extreme response to an infection that spreads to your blood. It’s a life-threatening medical emergency.

Why do I need a CRP test?

You may need this test if you have symptoms of a bacterial infection, such as:

Fever or chills

Rapid heart rate

Rapid breathing

Nausea and vomiting

You may also need a CRP test if your provider thinks you may have a chronic condition that causes inflammation. The symptoms will depend on the condition.

If you’ve already been diagnosed with an infection or a chronic disease that causes inflammation, you may need this test to monitor your condition and treatment. CRP levels rise and fall depending on how much inflammation is in your body. If your CRP levels fall, it’s a sign that your treatment for inflammation is working or you’re healing on your own.

What happens during a CRP test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This process usually takes less than five minutes.

What do the results mean?

Your CRP test results tell you how much inflammation you have in your body. But your test results can’t tell you what’s causing the inflammation. To make a diagnosis, your provider will look at your CRP results along with the results of other tests, your symptoms, and medical history.

In general, healthy people have very low amounts of CRP in their blood. Any increases above normal mean you have inflammation in your body. But labs measure CRP levels in different ways, and they define “normal” CRP ranges differently, so it’s best to ask your provider what your results mean.

Is there anything else I need to know about a CRP test?

A CRP test is sometimes confused with a high-sensitivity-(hs) CRP test. They both measure CRP, but they are used for different conditions. An hs-CRP test measures very tiny increases in your CRP levels. It is used to estimate your risk of heart disease.