Blood Gases & Acid-Base
Oxygen, carbon dioxide and acid-base balance, mostly measured in hospital settings.
11 tests explained
Common follow-up tests
- Arterial Blood pHHow acidic or basic your arterial blood is. The body holds it in a very narrow range, so small shifts matter.
- Arterial pCO2How much carbon dioxide is dissolved in your arterial blood. It shows how well your breathing clears this waste gas.
- Arterial pO2How much oxygen is dissolved in your arterial blood. It shows how well your lungs move oxygen into your blood.
- Base Excess (Base Deficit)A calculated number showing extra acid or base in your blood, apart from breathing. A negative value is a base deficit.
- Bicarbonate (HCO3-), Blood GasThe bicarbonate your blood gas analyzer calculates from pH and pCO2. It shows the kidney-controlled side of acid-base balance.
- Carboxyhemoglobin (COHb)The share of your hemoglobin that is bound to carbon monoxide instead of oxygen. It shows recent carbon monoxide exposure, including from smoking.
- Lactate (Lactic Acid)A byproduct of making energy that rises when cells are short of oxygen or the body can't clear it. Higher levels can be a sign the body is under strain.
- Methemoglobin (MetHb)The share of your hemoglobin in a form that can't carry oxygen well. Labs usually report up to about 1.5%, and higher levels can cause blue-gray skin.
- Oxygen Saturation, Arterial (SaO2)How much of the hemoglobin in your arterial blood is carrying oxygen, measured directly from a blood sample. Finger pulse oximeters estimate this same number.
- Venous Blood pHHow acidic or basic your blood is, measured in a sample from a vein. It runs a little lower than the arterial pH.
- Venous pCO2The pressure of carbon dioxide dissolved in blood from a vein. It reflects how well your lungs clear CO2 and runs a few mmHg above the arterial value.