Why would my anion gap be elevated if my kidney function and electrolytes look okay otherwise?

Expert Answer: The electrolytes that are typically measured are used to approximate the anion gap (AG). The electrolytes are a group of molecules with negative and positive charges and the body works to balance these charges. The electrolytes you see on your laboratory report aren't the only charged molecules at work in the body. Let's look at the way anion gap is calculated.

Sodium (Na+) and potassium (K+) have positive charges and are added together. Chloride (Cl-) and bicarbonate (HCO3-) are negatively charged and are added together. Here is the formula: (Na+ + K+) - (Cl- + HCO3-). You won't see bicarbonate (HCO3-) on your laboratory report because bicarbonate is calculated based on your carbon dioxide (CO2) measurement.

Further Explanation: Under normal conditions the gap between the positive charges and the negative charges isn't that big. Your laboratory report will show a reference range for a normal anion gap. If a negatively charged substance is in excess, your body can work to decrease the negatively charged electrolytes to balance out the charges. Even with good kidney function someone can have an abnormal anion gap in an effort to balance charges.

There are several reasons for this and you should ask your doctor about your potential causes and maybe even repeat the test. There are several possible causes for an increased anion gap. Examples include renal failure, ketoacidosis from starvation or diabetes, alcohol poisoning, salicylate poisoning, lactic acidosis, and elevated sodium to name a few.

The anion gap shows a possible disturbance in the balance of charges in the body.