⚗️ Anion Gap Calculator Na − (Cl + HCO₃), Albumin-Corrected
Enter Na, Cl, HCO₃ to compute anion gap. Add albumin for corrected AG — essential in critically ill and hypoalbuminemic patients.
ℹ️ For educational and reference use only. Does not replace professional medical diagnosis or treatment.
Units: mEq/L
Units: mEq/L
Units: mEq/L
Units: g/dL (enables corrected AG)
📊 Results
📋 Anion Gap Reference
| Category | AG (mEq/L) | Interpretation | Common Causes |
|---|---|---|---|
| Low | < 8 | Lab error or hypoalbuminemia | Hypoalbuminemia, lithium toxicity, multiple myeloma (+ charges) |
| Normal | 8 – 12 | Within reference | — |
| Elevated | 12 – 20 | Possible metabolic acidosis | Mild lactic acidosis, early renal failure, starvation ketosis |
| Markedly elevated | > 20 | Severe metabolic acidosis | DKA, lactic acidosis, toxic ingestion (MUDPILES) |
📝 MUDPILES — High-AG Metabolic Acidosis Differential
- M Methanol
- U Uremia (renal failure)
- D Diabetic ketoacidosis
- P Propylene glycol (lorazepam infusion)
- I Isoniazid, Iron
- L Lactic acidosis (sepsis, ischemia, metformin)
- E Ethylene glycol
- S Salicylates (aspirin toxicity)
📐 Formula
Anion Gap
AG = Na⁺ − (Cl⁻ + HCO₃⁻)
Albumin-Corrected AG
Corrected AG = AG + 2.5 × (4.0 − Albumin)
* Each 1 g/dL drop in albumin reduces measured AG by ≈ 2.5 mEq/L
* Normal albumin reference = 4.0 g/dL
AG = Na⁺ − (Cl⁻ + HCO₃⁻)
Albumin-Corrected AG
Corrected AG = AG + 2.5 × (4.0 − Albumin)
* Each 1 g/dL drop in albumin reduces measured AG by ≈ 2.5 mEq/L
* Normal albumin reference = 4.0 g/dL
❓ Frequently Asked Questions
What is the anion gap? ▼
The difference between measured cations (Na⁺) and measured anions (Cl⁻ + HCO₃⁻). It approximates unmeasured anions (lactate, ketones, sulfates, phosphates, albumin). Elevation signals a high-AG metabolic acidosis.
Why correct AG for albumin? ▼
Albumin carries most of the unmeasured negative charge. Hypoalbuminemia lowers AG by ~2.5 mEq/L per 1 g/dL albumin drop. Without correction, a "normal" AG may hide significant acidosis in a cirrhotic or ICU patient.
What is MUDPILES? ▼
Mnemonic for high-AG metabolic acidosis causes: Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates.
Causes of normal-AG (hyperchloremic) acidosis? ▼
Loss of HCO₃⁻ with Cl⁻ retention: diarrhea, RTA (types 1, 2, 4), ureteroenterostomy, carbonic anhydrase inhibitors, early renal failure. Mnemonic "HARDASS".
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⚠️ Disclaimer — Educational reference only; not for direct clinical decision-making. Interpret in the context of blood gas, osmolar gap, and clinical picture.
References: Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2(1):162-174.
References: Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2(1):162-174.