Anion Gap Calculation from Blood Chemistry Panel
Your doctor may calculate this value based on results from a blood test to help assess how well your kidneys are filtering waste products and whether your body is producing too much acid.
["This test helps identify acid-base imbalances in your blood."]
Key facts at a glance
- LOINC
- 41276-7
- Short code
- AG
- Synonyms
- Anion Gap Bld Calc-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lithium heparin (green-top) or serum separator tube (SST)
- Units
- N/A
- Ref low
- 8
- Ref high
- 16
- Critical range
- 4 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- calculated
- CPT
- 80051
- SNOMED
- 17327-2
- Specimen volume
- 1 mL whole blood
- Stability
- Room temperature: 2 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C): 1 week
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 25
- TAT
- 1–4 hours
- Order
- routine
What Is an Anion Gap?
The anion gap is a calculated measure derived from your blood test results. It compares the amount of negatively charged ions (anions) like chloride and bicarbonate to the positively charged ions (cations) like sodium and potassium. This difference can signal underlying health issues, such as metabolic acidosis or other imbalances.
How Is It Measured?
Your blood sample is analyzed for key electrolytes (sodium, potassium, chloride, and bicarbonate). The anion gap is calculated using the formula: (Na⁺ + K⁺) – (Cl⁻ + HCO₃⁻). This value is then interpreted by your healthcare provider.
When Might You Need This Test?
Doctors may order this calculation if you have symptoms like confusion, rapid breathing, nausea, or unexplained fatigue. It’s also used in cases of suspected metabolic acidosis, kidney disease, or poisoning.
What Does an Abnormal Gap Mean?
An elevated anion gap often points to conditions like diabetic ketoacidosis, kidney failure, or exposure to toxins. A normal gap suggests balanced electrolytes, but further testing may still be needed.
Reference range
8-16 mmol/L (with potassium); 8-12 mmol/L (without potassium)N/A
No special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Anion gap helps diagnose acid-base disorders by revealing whether the problem stems from low bicarbonate (metabolic acidosis) or other causes. It’s a critical tool for identifying conditions that require urgent medical attention.
Short name
Anion Gap
Frequently asked questions
Why do I need this test if I don’t have symptoms?
What are the most common causes of an elevated anion gap?
How long does it take to get results?
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 15, 2026. · Read our editorial policy