UMF^®2, NPA, and MGO are different but linear measurement units of grading systems used to indicate the anti-pathogenic potency of Manuka honey.

UMF^® or Unique Manuka Factor^® was the first industry standard developed to express the strength of the antimicrobial activity of the honey. It is therefore a well-established measurement unit, although MGO is fast becoming the primary unit used to express the antimicrobial activity of Manuka honey. The UMF^® rating shows, among other factors, the level of the honey’s ‘non-peroxide’ antimicrobial activity (NPA). The levels of NPA become the levels known as UMF^® units. UMF^® is a trademark owned by the Unique Manuka Factor Honey Association and can therefore only be used for honey packed into retail packs in New Zealand.

NPA or ‘non-peroxide’ activity expresses the level of anti-microbial activity of the honey. NPA is measured in %w/v phenol eq.

MGO or Methylglyoxal is the substance responsible for the antimicrobial property of Manuka honey. Research has shown that the content of this substance stands in direct and linear correlation to the level of NPA. Methylglyoxal is measured in mg/kg (ppm).