Adulteration has become an issue on the honey market in the past years and may occur unintentionally through feeding during nectar flow or by adding sugars/syrup to the honey. To ensure the quality and authenticity of honey it needs to be tested. For analysis of honey the availability of specific markers for processing, quality or especially for adulteration are important. The F/G ratio (fructose/glucose ratio) of a unifloral honey can be specific for its botanical origin. A F/G ratio <1.0 is rare and normally typical for rape (Brassica napus, also called canola) honey, additionally it could be observed that rice syrups have similar F/G values as rape honey. One particular marker for sugar adulteration in blossom honey is mannose. All measured natural blossom honeys showed no indication of mannose. We found out that mannose finds its way into blossom honey either through adulteration with high end syrups or through treatment with ion exchange resins as part of purifying processes.