What Is a Blood Oxygen Assessment?

A blood oxygen assessment is a specialist blood test that measures the levels of oxygen and carbon dioxide in your blood.

The results help us decide whether oxygen therapy would benefit you and, if needed, determine the safest and most effective amount of oxygen for you.

To ensure accurate results, the assessment should only be carried out when your condition is stable and you are not recovering from a chest infection.

If you become unwell before your appointment, please contact the Community Respiratory Specialist Team as your assessment may need to be rearranged.

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Why Am I Having This Test?

The assessment helps us understand how well oxygen is moving into your bloodstream and whether long-term oxygen therapy would be beneficial.

The test measures:

• Oxygen levels in your blood
• Carbon dioxide levels
• Blood acidity (pH)

If oxygen therapy is required, the results help us prescribe the correct oxygen flow rate for your needs.

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Why Might I Need Oxygen Therapy?

Some people with long-term lung conditions have lower-than-normal oxygen levels in their blood.

When oxygen levels remain low over time, it can place extra strain on important organs such as the heart and brain.

For people who need it, long-term oxygen therapy can:

• Increase oxygen levels in the blood
• Reduce strain on the body
• Support the health of vital organs
• Improve long-term health outcomes

Your healthcare professional will discuss whether oxygen therapy is appropriate based on your assessment results.

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What Happens During the Test?

Your assessment takes place while you’re sitting comfortably in a chair.

A small blood sample will be taken either:

• From an artery in your wrist (the preferred method), or
• From a blood vessel in your earlobe if a wrist sample isn’t suitable.

The sample is analysed immediately.

If your oxygen levels are satisfactory, no further testing may be needed.

If your oxygen levels are lower than expected, you’ll be asked to breathe oxygen through a small nasal cannula (soft tubes placed just inside your nostrils) for up to 30 minutes.

A second blood sample is then taken to see how your body responds to oxygen.

Occasionally, a third sample may be needed to determine the correct oxygen prescription.

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Will the Test Hurt?

The blood test is quick and straightforward.

You may experience:

• A brief sharp sensation when the sample is taken
• Mild discomfort during the procedure
• Minor bruising around the wrist afterwards

If you have any concerns during your appointment, please speak to the nurse or physiotherapist carrying out the assessment.

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Preparing for Your Appointment

The assessment can take between 30 minutes and two hours, depending on whether oxygen testing is required.

Before attending, please:

• Allow enough time for your appointment
• Bring a drink or light snack if you wish
• Remove any earrings before arriving
• Avoid wearing nail varnish or false nails, as these can affect oxygen monitoring
• Drink plenty of fluids beforehand

These simple steps help us obtain the most accurate results.

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During Your Appointment

During your visit we’ll:

• Explain each stage of the assessment
• Answer any questions you may have
• Discuss your results with you
• Explain whether any further treatment or oxygen therapy is recommended

Our aim is to make sure you understand your results and any next steps before you leave.

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Further Information

If you have any questions about your blood oxygen assessment or need to rearrange your appointment because you are unwell, please contact the Community Respiratory Specialist Team.

Telephone: 0300 124 5909

Opening Hours: Monday to Friday, 9:00am – 5:00pm