Anion Gap

Overview

The anion gap is a measure used to detect changes in the balance of chemicals (ions) in your blood. It compares the amount of positively charged ions (like sodium) with negatively charged ions (like chloride and bicarbonate). When the anion gap is higher than normal, it can suggest there are unusual substances in your blood, which might be a sign of specific health issues such as metabolic problems or certain types of poisoning.

Testing Levels:

• High (19 mmol/L) - An elevated anion gap reading in a blood test typically suggests the presence of excess acids or abnormal substances in the bloodstream that are not accounted for by the usual measured ions (sodium, chloride, bicarbonate). This finding often indicates metabolic acidosis, where the body either produces too much acid, loses too much base (bicarbonate), or cannot effectively remove acids through the kidneys. Conditions such as diabetic ketoacidosis, lactic acidosis (often seen in severe infections or shock), renal failure, and certain toxins or medications (like ethylene glycol or methanol) can all lead to an elevated anion gap.
  
  
• Mid - A normal anion gap in a blood test signifies that the levels of positively charged ions (cations) and negatively charged ions (anions) in the blood are balanced within expected parameters. This balance typically reflects stable acid-base conditions in the body, where the production, clearance, and distribution of acids and bases are functioning normally. In clinical practice, a normal anion gap is reassuring, indicating that there are no significant excesses of unmeasured acids or bases that could indicate metabolic disturbances or underlying health issues.
  
  
• Low (8 mmol/L) - A low anion gap in a blood test suggests a decrease in the balance between positively charged ions (cations) and negatively charged ions (anions). This can be due to conditions like low albumin levels, certain types of blood disorders such as multiple myeloma or IgG monoclonal gammopathy, bromide toxicity, or hypercalcemia. It's less common than a high anion gap and usually requires further investigation to determine the specific underlying cause.

Why We Test Anion Gap

What Affects It

Several factors can influence the anion gap, a measure used in pathology to assess the balance of electrolytes and acids in the body. Changes in levels of substances like sodium, potassium, chloride, and bicarbonate directly affect the calculation of the anion gap. Conditions that alter the body's acid-base balance, such as metabolic acidosis or alkalosis, can also impact the anion gap: acidosis typically raises it, while alkalosis tends to lower it. Kidney function plays a crucial role in maintaining electrolyte balance, which in turn affects the anion gap. Additionally, medications and various diseases or disorders can contribute to fluctuations in the anion gap by influencing electrolyte levels and acid-base status.

How to Improve

Common Name: Anion Gap