Calculate Basic Anion Gap
Normal anion gap
Did our AI summary help? Let us know.
Evidence-based calculations Used in clinical settings worldwide Regular monitoring recommended
Ready to run the numbers?
Why: This calculation helps assess important health parameters for clinical and personal wellness tracking.
How: Enter your values above and the calculator will apply validated formulas to compute your results.
Run the calculator when you are ready.
Normal Electrolytes
Healthy 35-year-old with normal lab values
Click to load
Diabetic Ketoacidosis
28-year-old Type 1 diabetic with DKA, glucose 450 mg/dL
Click to load
Lactic Acidosis - Sepsis
62-year-old with septic shock, lactate 8.5 mmol/L
Click to load
Chronic Kidney Disease
70-year-old with stage 4 CKD, BUN 85 mg/dL
Click to load
Toxic Alcohol Ingestion
45-year-old suspected methanol poisoning
Click to load
Primary Electrolytes
Additional Labs
Patient Information
Results
12.0
Anion Gap (mEq/L)
12.0
Corrected AG
0.0
Delta Gap
0.00
Delta Ratio
NORMAL - Low clinical concern
Normal anion gap. No significant metabolic acidosis detected.
Possible Causes (MUDPILES)
- Normal - no pathological cause identified
Clinical Recommendations
- No immediate intervention required
- Continue routine monitoring as clinically indicated
Visualizations
Electrolyte Distribution
Anion Gap Comparison
Step-by-Step Calculation
Step 1: Calculate Basic Anion Gap
Formula: AG = Na - (Cl + HCO3)
Calculation: AG = 140 - (104 + 24)
Result: 12.0 mEq/L
The anion gap represents unmeasured anions in serum. Normal range is 8-12 mEq/L.
Step 2: Correct for Albumin
Formula: ext{Corrected} ext{AG} = ext{AG} + 2.5 imes (4 - ext{Albumin})
Calculation: Corrected AG = 12.0 + 2.5 ร (4 - 4)
Result: 12.0 mEq/L
Albumin contributes to unmeasured anions. Low albumin falsely lowers the AG.
Step 3: Calculate Delta Gap
Formula: ext{Delta} ext{Gap} = ext{Corrected} ext{AG} - 12
Calculation: Delta Gap = 12.0 - 12
Result: 0.0 mEq/L
Delta gap represents the excess anion gap above normal (12 mEq/L).
Step 4: Calculate Delta Ratio
Formula: ext{Delta} ext{Ratio} = ext{Delta} ext{AG} / ext{Delta} HCO3
Calculation: Delta Ratio = 0.0 / |24 - 24|
Result: 0.00
Delta ratio helps identify mixed acid-base disorders. Ratio 1-2 = pure HAGMA.
What is the Anion Gap?
Definition
The anion gap represents the difference between measured cations (sodium, potassium) and measured anions (chloride, bicarbonate) in blood serum. It reflects unmeasured anions like albumin, phosphate, and organic acids.
Normal Range
The normal anion gap is 8-12 mEq/L without potassium, or 12-16 mEq/L when potassium is included. Values above this range indicate high anion gap metabolic acidosis (HAGMA).
Clinical Importance
An elevated anion gap is a critical finding that helps identify life-threatening conditions like diabetic ketoacidosis, lactic acidosis, toxic ingestions, and kidney failure.
How Does the Anion Gap Work?
The principle of electroneutrality requires that the total positive charges (cations) equal total negative charges (anions) in body fluids. The anion gap calculation reveals unmeasured anions that accumulate in metabolic acidosis.
MUDPILES Mnemonic
- M - Methanol
- U - Uremia
- D - Diabetic ketoacidosis
- P - Propylene glycol, Paraldehyde
- I - Iron, Isoniazid
- L - Lactic acidosis
- E - Ethylene glycol
- S - Salicylates
Delta Ratio Interpretation
- < 1: Mixed HAGMA + NAGMA
- 1-2: Pure HAGMA
- > 2: HAGMA + metabolic alkalosis
When to Calculate Anion Gap?
Emergency Department
Essential for evaluating altered mental status, suspected overdose, diabetic emergencies, sepsis, and unexplained acidosis. Calculate immediately with any abnormal basic metabolic panel.
ICU Monitoring
Track trends in critically ill patients, monitor response to treatment, detect developing complications, and guide fluid and electrolyte management.
Chronic Disease Management
Monitor patients with chronic kidney disease, diabetes on metformin, chronic alcohol use, or those on medications affecting acid-base balance.
Anion Gap Differential Diagnosis
| Category | Condition | Unmeasured Anion | Key Labs/Features |
| Ketoacidosis | Diabetic (DKA) | ฮฒ-hydroxybutyrate, acetoacetate | High glucose, positive ketones |
| Alcoholic | ฮฒ-hydroxybutyrate | History of alcohol, low/normal glucose | |
| Starvation | Ketone bodies | Fasting history, mild acidosis | |
| Lactic Acidosis | Type A (hypoxic) | Lactate | Shock, hypoxia, lactate >4 |
| Type B (non-hypoxic) | Lactate | Metformin, liver failure, malignancy | |
| Renal Failure | Uremia | Sulfate, phosphate, urate | High BUN/Cr, GFR <20 |
| Toxic Ingestions | Methanol | Formate | Visual changes, osmolar gap early |
| Ethylene glycol | Glycolate, oxalate | Calcium oxalate crystals, AKI | |
| Salicylates | Salicylic acid, lactate, ketones | Mixed AG acidosis + resp alkalosis |
Non-Anion Gap Metabolic Acidosis (NAGMA)
GI Bicarbonate Loss (UAG Negative)
- โข Diarrhea (most common)
- โข Ileostomy, fistula
- โข Ureterosigmoidostomy
- โข Cholestyramine use
Renal Causes (UAG Positive)
- โข Type 1 (Distal) RTA - Urine pH >5.5, hypokalemia
- โข Type 2 (Proximal) RTA - HCO3 wasting
- โข Type 4 RTA - Hyperkalemia, hypoaldosteronism
- โข Early CKD (before AG rises)
Tip: Use Urine Anion Gap to differentiate GI from renal causes. Negative UAG = GI loss, Positive UAG = RTA
Formulas and Calculations
Basic Anion Gap
AG = Na - (Cl + HCO3)
Normal range: 8-12 mEq/L
Anion Gap with Potassium
AG = (Na + K) - (Cl + HCO3)
Normal range: 12-16 mEq/L (when including K+)
Albumin-Corrected Anion Gap
Corrected AG = AG + 2.5 ร (4 - Albumin)
Each 1 g/dL decrease in albumin lowers AG by approximately 2.5 mEq/L
Delta Gap (Delta-Delta)
Delta Gap = (AG - 12) - (24 - HCO3)
Helps identify mixed acid-base disorders
Related Calculators
Winters Formula
Expected pCO2 in metabolic acidosis
Serum Osmolality
Calculate osmolar gap
Sodium Correction
Corrected sodium for glucose
ABG Analyzer
Complete acid-base analysis
Bicarbonate Deficit
Calculate bicarbonate replacement
Urine Anion Gap
Evaluate renal acid handling
Free Water Deficit
Calculate free water needs
GFR Calculator
Estimate kidney function
Frequently Asked Questions
What causes a high anion gap?
High anion gap metabolic acidosis (HAGMA) occurs when unmeasured anions accumulate in the blood. Common causes include diabetic ketoacidosis (ketone bodies), lactic acidosis (lactate), uremia (organic acids), and toxic ingestions (methanol, ethylene glycol metabolites).
Why correct for albumin?
Albumin is a major unmeasured anion. Low albumin (common in critically ill patients) can mask a true elevation in anion gap. For every 1 g/dL decrease in albumin below 4 g/dL, the anion gap appears approximately 2.5 mEq/L lower than it actually is.
What is the delta ratio used for?
The delta ratio (delta gap / delta bicarbonate) helps identify mixed acid-base disorders. A ratio of 1-2 indicates pure HAGMA. A ratio less than 1 suggests concurrent non-anion gap acidosis, while greater than 2 suggests pre-existing metabolic alkalosis or chronic respiratory acidosis.
Clinical Pearls
Always Correct for Albumin
In critically ill patients with hypoalbuminemia, the uncorrected AG may appear normal despite significant acidosis.
Check Osmolar Gap Too
When HAGMA is present with unclear etiology, calculate the osmolar gap to evaluate for toxic alcohols.
Lactate is Key
Lactic acidosis is the most common cause of HAGMA in hospitalized patients. Always check lactate levels.
Trend Over Time
Serial AG measurements help monitor treatment response and detect developing complications.
For informational purposes only โ not medical advice. Consult a healthcare professional before acting on results.
๐ฅ Health Facts
โ WHO
โ CDC
Related Calculators
Sodium Correction Calculator - Hyperglycemia Glucose Correction
Calculate corrected sodium for hyperglycemia in DKA and HHS. Adjust measured sodium based on glucose levels.
healthCorrected Magnesium Calculator - Albumin Adjustment
Calculate corrected magnesium for hypoalbuminemia. Assess true magnesium status when albumin is low.
healthBicarbonate Deficit Calculator - NaHCO3 Replacement
Calculate bicarbonate deficit for metabolic acidosis treatment. Determine sodium bicarbonate replacement needs.
healthCorrected Calcium Calculator - Albumin Adjustment
Calculate corrected calcium for hypoalbuminemia using standard correction formulas. Assess true calcium status.
healthPlasma Osmolality Calculator - Osmolar Gap and Tonicity
Calculate plasma osmolality, effective osmolality (tonicity), and osmolar gap for comprehensive fluid and electrolyte assessment.
healthUrine Anion Gap Calculator - NAGMA Differential
Calculate urine anion gap to differentiate GI versus renal causes of non-anion gap metabolic acidosis (NAGMA).
health