Baseexcessbldcalcscnc
A test that measures the amount of excess base or acid in your blood, helping doctors evaluate your acid-base balance and identify metabolic disorders.
{"Base excess measures the metabolic component of your blood's acid-base balance","Positive values indicate metabolic alkalosis (too alkaline); negative values indicate metabolic acidosis (too acidic)","This test helps doctors distinguish between respiratory and metabolic causes of acid-base imbalance","Results are calculated from other blood gas measurements","Normal range is typically -2 to +2 mEq/L"}
Key facts at a glance
- LOINC
- 11555-0
- Short code
- Base excess Bld Calc-sCnc
- Synonyms
- Base excess Bld Calc-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- calculated
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
The base excess test measures the amount of strong acid needed to titrate (neutralize) a liter of your fully oxygenated blood to a normal pH of 7.4. This is a calculated value derived from other measurements in arterial blood gas analysis, including pH, oxygen, and carbon dioxide levels. Unlike simple pH measurements, base excess specifically shows the metabolic (non-respiratory) component of your acid-base balance.
Why do I need this test?
Your doctor may order this test if you have symptoms of an acid-base imbalance, such as difficulty breathing, confusion, nausea, or weakness. It helps determine whether your blood is too acidic (acidosis) or too alkaline (alkalosis) and whether the problem is due to metabolic causes (like kidney function or medication) or respiratory causes (like lung function). The test is commonly used in emergency rooms, intensive care units, and when monitoring patients with chronic conditions like kidney disease or diabetes.
How is the test performed?
A healthcare professional will draw a small sample of blood, usually from an artery in your wrist (radial artery) or sometimes from a vein. The sample is then analyzed using a blood gas analyzer that calculates the base excess value along with other parameters like pH, oxygen, and carbon dioxide levels. The procedure is quick, though arterial blood draws may be slightly more uncomfortable than venous draws. Results are typically available within minutes to an hour.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
Do I need to fast before this test?
Can base excess be treated?
Is this test dangerous?
How long does it take to get results?
Sources
- 1
- 2
- 3
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