Anion Gap (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 and whether your body is producing too much acid.
["The anion gap helps identify metabolic imbalances, especially acid-base disorders."]
Key facts at a glance
- LOINC
- 73578-7
- Short code
- AGV
- Synonyms
- Anion Gap BldV Calculated.4Ions-sCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lithium heparin (green-top) or sodium heparin tube for venous whole blood collection; alternatively serum separator tube (SST)
- Units
- N/A
- Ref low
- 8
- Ref high
- 16
- Critical range
- 6 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- calculated-ions
- CPT
- 80051
- SNOMED
- 271058007
- Specimen volume
- 1-3 mL of whole blood
- Stability
- Plasma/serum stable for 2 hours at room temperature, 8 hours refrigerated at 2-8°C, and 1 week frozen at -20°C
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 25
- TAT
- 1–4 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test if you have symptoms like confusion, shortness of breath, muscle weakness, or unexplained nausea/vomiting. It’s also used to check for conditions like diabetic ketoacidosis, kidney failure, or poisoning by certain toxins that alter ion balance.
What to Expect Before the Test
No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm) to draw blood. It usually takes a few minutes. If you’re nervous, let your doctor or nurse know—you can take pain relievers beforehand if needed.
What the Results Mean
The test result compares your blood’s sodium, chloride, and bicarbonate levels. A higher gap may suggest conditions like diabetic ketoacidosis or poisoning, while a lower gap could indicate overuse of certain medications (e.g., bicarbonate-based antacids). Your doctor will discuss these findings with you.
Common Conditions Linked to Anion Gap
High anion gaps often point to metabolic acidosis caused by factors like kidney problems, alcohol poisoning, or drugs that break down into acids. Low anion gaps may occur with overhydration, certain medications, or rare blood disorders.
Reference range
Adult venous blood: 8-16 mEq/L (with potassium); 8-12 mEq/L (without potassium). Pediatric ranges may vary by age.N/A
No special patient preparation required. Fasting is not necessary for anion gap calculation.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Anion Gap
Frequently asked questions
What causes a high anion gap in my blood test results?
How often should I get this test?
Can I eat or drink before this test?
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