<prompt> Stool osmotic gap is calculated by using the formula:2 x stool stool2 x stool stool2 x stool stool2 x stool stool  <response>: Stool osmotic gap is calculated by using the formula : 2 x stool stool stool osmolality When it is 50, an osmotic gap is present, suggests diarrhea is due to a non absorbed dietary nutrient, e.g., a fatty acid andor carbohydrate. When this difference is 25, a dietary nutrient is not responsible for the diarrhea. Ref: Harrison, E-18, P-2460. 