Arterial Blood Gas
An ABG measures how well the lungs are moving oxygen in and carbon dioxide out, and whether the blood is too acidic or too alkaline. It is taken from an artery, almost always in hospital, in someone who is acutely unwell.
This is an educational reading aid, not a diagnosis and not medical advice. Reference ranges differ between laboratories — always read the range printed on your own report. Nothing here can see you, your history or your medicines. Do not start, stop or change any treatment on the strength of this page: take your report to a qualified doctor.
Reference ranges reviewed by Dr. Mohan Gayenlast reviewed
Your values
Fill in only the ones on your report. Anything you leave blank is simply skipped.
How acidic or alkaline the blood is. The tightest-controlled number in the body.
Carbon dioxide in the blood — controlled by breathing. The RESPIRATORY half of acid–base.
Oxygen dissolved in arterial blood. Only meaningful alongside how much oxygen was being breathed.
The METABOLIC half of acid–base, managed by the kidneys.
How much acid or base would have to be added to bring the pH back to normal.
Rises when tissues are not getting enough oxygen. One of the most useful single numbers in a sick patient.
Enter one or more values and your reading will appear here.
What this panel is easy to get wrong
- THIS IS AN ACUTE HOSPITAL TEST. If you are holding an ABG result, the person it belongs to is being actively looked after — this page is to help you follow the conversation, not to replace it.
- pO₂ falls with altitude and rises with supplemental oxygen. A pO₂ means nothing without knowing how much oxygen the person was breathing.
- The pattern is what matters: pH says which way, pCO₂ says whether the lungs are the cause, bicarbonate says whether the metabolism or the kidneys are, and the two together say whether the body has had time to compensate.
Where these ranges come from: Commonly published values for an arterial sample at sea level, breathing room air.
Where this is written from: This site is written from Indian clinical practice. Drug availability and brand names, vaccination schedules, national health programmes and some reference cut-offs differ between countries — a schedule or a threshold that is standard here may not be standard where you are. If you are reading outside India, check anything on this page against your own country’s guidance before you act on it.
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pH, pCO₂, pO₂, bicarbonate, base excess and lactate.