Anion Gap Calculator

mEq/L
Please enter a valid sodium level (100-180 mEq/L).
mEq/L
Please enter a valid chloride level (70-130 mEq/L).
mEq/L
Please enter a valid bicarbonate level (10-40 mEq/L).
mEq/L

Understanding Anion Gap

The anion gap is a calculated value that helps assess the acid-base balance in the body. It represents the difference between the measured cations (positively charged ions) and the measured anions (negatively charged ions) in the serum.

Normal Range: Typically 8-12 mEq/L (without potassium) or 12-16 mEq/L (with potassium).

High Anion Gap: May indicate metabolic acidosis, which can be caused by conditions such as kidney failure, diabetic ketoacidosis, lactic acidosis, or ingestion of certain toxins.

Low Anion Gap: Less common, but may be seen in conditions like hypoalbuminemia or multiple myeloma.

Clinical Significance of Anion Gap

The anion gap is a valuable tool in the differential diagnosis of acid-base disorders. It helps clinicians determine the underlying cause of metabolic acidosis and guide appropriate treatment.

Causes of High Anion Gap Acidosis (MUDPILES)

  • Methanol
  • Uremia (kidney failure)
  • Diabetic ketoacidosis
  • Paraldehyde
  • Iron, Isoniazid
  • Lactic acidosis
  • Ethylene glycol
  • Salicylates (aspirin)

Causes of Normal Anion Gap Acidosis (HARDUP)

  • Hyperalimentation
  • Acetazolamide
  • Renal tubular acidosis
  • Diarrhea
  • Uretero-enteric fistula
  • Pancreaticoduodenal fistula

Limitations of Anion Gap

  • May be affected by changes in albumin levels
  • Does not identify the specific cause of acidosis
  • Requires consideration of other clinical factors

When to Use Anion Gap

Anion gap calculation is useful in the following situations:

  • Evaluating patients with altered mental status
  • Assessing patients with suspected metabolic disturbances
  • Monitoring patients with kidney disease or diabetes
  • Investigating the cause of unexplained acidosis