The stool pH test measures the acidity or alkalinity of a stool sample. Normal stool pH is typically slightly acidic to neutral (around 6–7).This test helps assess digestive function and carbohydrate absorption. A low (acidic) stool pH may indicate carbohydrate malabsorption, such as lactose intolerance or bacterial fermentation in the gut, while a high (alkaline) stool pH may be seen in some infections or other digestive disorders.