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The normal range of the anion gap is 6 - 11 mEq/L. Anything above 11 mEq/L is considered as high anion gap. A value less than 3 is considered low anion gap.
The anion gap provides an estimation of the unmeasured anions in the plasma and is useful in the setting of arterial blood gas analysis. Its basic premise is based on the fact that electroneutrality must exist in the body, or in other words the net charges of serum anions, which includes albumin, bicarbonate, chloride, organic acids and phosphate must equal the net charges of the serum cations, which includes calcium, magnesium, potassium and sodium.
A low anion gap is frequently caused by hypoalbuminemia. In hypoalbuminaemia the anion gap is reduced from between 2.5 to 3 mmol/L per 1 g/dL decrease in serum albumin.
You might consult with your doctor for a examination and additional tests to confirm the cause and also guide effective therapy.