Phbld
A blood pH test measures the acidity or alkalinity of your blood to evaluate your body's acid-base balance.
{"Blood pH normally ranges from 7.35 to 7.45","Abnormal pH may indicate kidney, lung, or metabolic problems","The test is performed on a blood sample from a vein","Results help doctors diagnose conditions like acidosis or alkalosis"}
Key facts at a glance
- LOINC
- 11558-4
- Short code
- pH Bld
- Synonyms
- pH Bld
- 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?
A blood pH test measures how acidic or alkaline your blood is. The pH scale ranges from 0 to 14, with 7 being neutral. Your blood should be slightly alkaline, with a normal pH between 7.35 and 7.45. This test is part of an arterial blood gas (ABG) test or venous blood gas test that evaluates your body's acid-base balance.
Why is it done?
Your doctor may order a blood pH test if you have symptoms of an acid-base imbalance, such as difficulty breathing, confusion, nausea, or fatigue. It helps diagnose and monitor conditions like kidney disease, lung disease, metabolic disorders, severe infections, or poisoning. The test is also used to monitor patients on ventilators or those undergoing certain treatments.
How is it performed?
A healthcare professional will draw a blood sample from a vein in your arm using a needle. For arterial blood gas testing, the sample may be taken from an artery, usually in the wrist. The sample is then analyzed in a laboratory to measure the pH level and other parameters like oxygen and carbon dioxide levels.
Understanding your results
A pH below 7.35 indicates acidosis, meaning your blood is too acidic. This can be caused by conditions like diabetic ketoacidosis, kidney failure, or severe diarrhea. A pH above 7.45 indicates alkalosis, meaning your blood is too alkaline. This may be due to hyperventilation, vomiting, or certain medications. Your doctor will interpret your results along with other test values to determine the cause and appropriate treatment.
Reference range
7.35-7.45not specified
No fasting required; patient should be at rest; arterial sample preferred for accurate blood gas pH
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Do I need to fast before the test?
Is the test painful?
What can affect my blood pH levels?
How often will I need this test?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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