Based on the reactivity with Tollen’s, Benedict’s or Fehling’s reagent, carbohydrates are classified as; Reducing sugars Carbohydrates that can reduce Tollen’s, Benedict’s or Fehling’s reagents are called reducing sugars (sugar with free aldehyde or ketone group). All monosaccharides and most of the disaccharides are reducing sugars. Some examples are Maltose and Lactose. Non-reducing sugars Carbohydrates that cannot reduce Tollen’s, Benedict’s or Fehling’s reagents are called non-reducing sugars. Sucrose is a non-reducing sugar.