Anion Gap in Blood (Calculated from Serum Ions)
This test measures the difference between positively charged ions (like sodium) and negatively charged ions (like chloride and bicarbonate) in your blood. It helps assess how well your kidneys are filtering waste products and whether your body has an abnormal buildup of acids.
["The anion gap helps identify metabolic imbalances, such as kidney issues or acid-base disorders."]
Key facts at a glance
- LOINC
- 73579-5
- Short code
- Anion Gap BldMV Calculated.4Ions-sCnc
- Synonyms
- Anion Gap BldMV Calculated.4Ions-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-ions
- 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 the Anion Gap Used For?
Doctors use the anion gap to diagnose conditions like kidney failure, diabetic ketoacidosis, or poisoning from certain toxins. It can also help determine if your body is retaining too much acid, which may require medical treatment.
How Is This Test Performed?
A small blood sample is drawn from your arm. The lab analyzes the serum portion of your blood to calculate the anion gap by comparing sodium, chloride, and bicarbonate levels.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms like confusion, shortness of breath, nausea, or if they suspect metabolic acidosis (too much acid in your blood). It’s also used in monitoring certain chronic conditions.
What Are Common Causes?
High anion gaps often occur due to conditions like diabetic ketoacidosis, kidney problems, or exposure to toxins. Low anion gaps are less common but may happen with certain electrolyte imbalances or medications.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The anion gap is clinically significant because it provides insight into metabolic disturbances. Elevated gaps often indicate conditions requiring urgent medical evaluation, while normal or low gaps suggest other underlying issues may need further investigation.
Short name
Anion Gap
Frequently asked questions
Why do I need this test if I don’t have symptoms?
What does a high anion gap mean?
Can I affect my results by diet or medications?
Sources
- 1
- 2Lab Tests OnlineSource
- 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