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Diagnostic Test Information: Purpose, Procedure, and How to Understand Your Results

Published: July 31, 2026Updated: August 16, 2026

This test measures the acidity or alkalinity of your arterial blood, helping doctors evaluate your body's acid-base balance and overall health status.

Quick summary

{"Measures blood acidity level (normal pH: 7.35-7.45)","Helps diagnose breathing, kidney, or metabolic problems","Requires arterial blood sample (usually from wrist)","Results guide treatment for acid-base imbalances","Abnormal results may indicate serious health conditions"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
2744-1
Short code
pH BldA
Synonyms
pH BldA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
not specified
Ref low
7.35
Ref high
7.45
Critical range
7.2 not specified – 7.6 not specified
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test, and what does it measure or help your healthcare professional evaluate?

The arterial blood pH test measures how acidic or alkaline your arterial blood is. The pH scale ranges from 0 to 14, with 7.0 being neutral. Your blood should normally be slightly alkaline, with a pH between 7.35 and 7.45. This test is part of an arterial blood gas (ABG) analysis that also measures oxygen and carbon dioxide levels in your blood.

Why do I need this test, and how might the results help guide my diagnosis, treatment, or follow-up care?

Your doctor may order this test if you have symptoms of an acid-base imbalance, such as difficulty breathing, confusion, nausea, or rapid heartbeat. It is also used to monitor lung and kidney function, evaluate the effectiveness of oxygen therapy, and assess conditions like pneumonia, COPD, kidney disease, or metabolic disorders.

How is the test performed, and what should I expect before, during, and after the procedure?

A healthcare professional will draw blood from an artery, typically in your wrist. The sample is then analyzed immediately to measure pH and other blood gas levels. You may feel a brief sharp pain or discomfort during the arterial puncture. Pressure will be applied to stop the bleeding afterward.

Understanding your results: Your healthcare professional will explain what the findings mean, whether they are within the expected range, and whether additional testing or follow-up is needed.

A pH below 7.35 indicates acidosis (blood is too acidic), while a pH above 7.45 indicates alkalosis (blood is too alkaline). Both conditions can be caused by various factors including lung or kidney problems, diabetes, severe infections, or certain medications. Your doctor will interpret your results alongside other test values to determine the cause and appropriate treatment.

Reference range

7.35-7.45not specified

Specimen: serum

No fasting required; arterial sample collected anaerobically by trained personnel

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Arterial blood pH is a critical indicator of your body's acid-base balance. Abnormal pH levels can signal respiratory disorders (such as asthma, COPD, pneumonia), metabolic conditions (such as diabetes or kidney disease), or poisoning. This test helps doctors diagnose the underlying cause of acid-base imbalances and monitor the effectiveness of treatments such as mechanical ventilation or medication. Prompt diagnosis and treatment of pH abnormalities are essential to prevent complications affecting vital organs.

Frequently asked questions

Is the arterial blood pH test different from a regular blood test?
Yes. Regular blood tests use venous blood drawn from a vein in your arm. The arterial blood pH test requires arterial blood, usually from the wrist artery. Arterial blood better reflects how your lungs are exchanging oxygen and carbon dioxide compared to venous blood.
Does the test hurt?
You may feel a sharp pain or discomfort when the needle punctures the artery. However, the pain is usually brief. Some people experience soreness, bruising, or a small lump at the puncture site afterward. Applying pressure as instructed by your healthcare provider can help reduce bruising.
What can cause abnormal blood pH?
Many conditions can affect blood pH. Respiratory causes include asthma, COPD, pneumonia, lung infections, and respiratory failure. Metabolic causes include diabetes (especially diabetic ketoacidosis), kidney failure, severe infections, and certain medications or poisoning. Lifestyle factors like extreme exercise, dehydration, or extreme diet changes can also temporarily affect pH levels.
How is abnormal blood pH treated?
Treatment depends on the underlying cause and severity. For acidosis, treatment may include oxygen therapy, mechanical ventilation, IV fluids, or medications to help restore balance. For alkalosis, treatment may involve addressing the root cause, such as treating infections, stopping certain medications, or correcting electrolyte imbalances. Your doctor will create a treatment plan based on your specific condition.
Do I need to prepare for the test?
Your doctor will provide specific instructions. You may need to avoid smoking before the test, as it can affect results. Inform your doctor about any medications you are taking, as some can influence blood pH. No fasting is typically required for this test. If you have a bleeding disorder or take blood thinners, tell your healthcare provider before the test.
  1. 1
    Mayo Clinic - Blood pH TestSource
  2. 2
    MedlinePlus - Arterial Blood Gas TestSource
  3. 3
    Cleveland Clinic - Arterial Blood Gas (ABG) TestSource

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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy