The most popular application of Fehling’s test is to identify and determine whether the carbonyl group concerned is a ketone or an aldehyde. Aldehydes tend to be oxidised and display positive results. Ketones, except the alpha-hydroxy-ketones, do not display any kind of reaction.
Fehling’s test is also generally used for monosaccharides, commonly known as simple sugars, along with other reducing sugars. In terms of monosaccharides, it displays positive results not only for aldose monosaccharides but also for ketose monosaccharides, since ketoses are transformed into aldoses through the base contained in the reagent.
It is used to determine the presence of glucose in the urine. It is applied to identify diabetes as being prevalent in the person.
Fehling’s test is also applied for the breaking down of starch to convert it into glucose syrup along with maltodextrins.