What could cause a low Anion Gap?

A low anion gap is typically defined as an anion gap less than the normal reference range, which is usually around 8-12 mEq/L. One of the common causes of a low anion gap is hypoalbuminemia, which refers to low levels of albumin in the blood.

Albumin is a negatively charged protein that contributes to the overall anion gap calculation. When albumin levels decrease, the concentration of negatively charged ions in the plasma also decreases, which can lead to a lower anion gap. This decrease is significant because albumin commonly makes up a large part of the measured anions. Therefore, in cases of hypoalbuminemia, the reduction in albumin can directly result in a lower anion gap, making it a clear and straightforward explanation for this phenomenon.

Other causes, such as renal failure or excessive bicarbonate, typically lead to a high anion gap rather than a low one, and conditions such as ketoacidosis are characterized by a high anion gap due to the accumulation of organic acids. Thus, hypoalbuminemia stands out as a primary cause for a decrease in the anion gap.