Bicarbonate
What this test measures
Bicarbonate is the body's main buffer against acid. It is regulated by the kidneys and by breathing, and its level in the blood reflects the balance between acid produced and acid removed. The test measures the concentration in a blood sample.
Why doctors request it
It is printed on many U&E panels and helps doctors judge the body's acid balance, for example in kidney disease, diabetes, prolonged vomiting or diarrhoea, and in some lung conditions.
What commonly pushes it up
- Prolonged vomiting, which loses stomach acid
- Water tablets
- Long-standing lung conditions where carbon dioxide builds up
- Some antacids and bicarbonate tablets
- Adrenal hormone excess
What commonly pushes it down
- Reduced kidney filtering, where acid is not cleared
- Diarrhoea
- Uncontrolled diabetes
- Very hard exercise or a short-term severe illness
- Some medicines such as acetazolamide and metformin in certain situations
- Over-breathing, as in panic or at altitude
Everyday reasons for a value outside the range
- A sample left open to the air loses carbon dioxide and reads lower
- A delay before the lab lowers the reading
- US reports label it 'CO2', which is the same measurement, not a blood gas
About the sample
No fasting needed. Best measured on a fresh sample; delayed samples read low.
Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.
Read my report freeThis is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.