UMF and MGO are two rating systems printed on manuka honey labels that tell you how potent the honey is. MGO stands for methylglyoxal, the naturally occurring compound responsible for manuka honey’s antibacterial properties. UMF stands for Unique Manuka Factor, a broader grading system that tests for MGO plus several other chemical markers to verify both potency and authenticity. The two scales measure overlapping things, but they’re not identical.
MGO: The Active Compound
Methylglyoxal is a compound that forms naturally in manuka honey and gives it antibacterial strength that other honeys don’t have. Most honeys produce some germ-fighting activity through hydrogen peroxide, but manuka honey has a second, separate mechanism driven by MGO. When researchers tested MGO directly against common bacteria like E. coli and Staph aureus, it showed clear antibacterial effects on its own.
The MGO number on a jar tells you the concentration of methylglyoxal in milligrams per kilogram of honey. An MGO 100+ jar contains at least 100 mg/kg, while an MGO 700+ jar contains at least 700 mg/kg. Higher numbers mean more methylglyoxal and stronger antibacterial activity.
MGO doesn’t come from the bees. It forms from a precursor compound called dihydroxyacetone (DHA) found in the nectar of the manuka bush. Fresh manuka honey starts with high DHA and relatively low MGO, but as the honey ripens and ages, DHA steadily converts into MGO at roughly a 2:1 ratio. This is a natural chemical process. Heating honey doesn’t speed it up or create artificial MGO through caramelization.
UMF: The Broader Quality Test
The UMF grading system was developed after research pioneered by Dr. Peter Molan at the University of Waikato in New Zealand during the 1980s. Molan’s early work identified that manuka honey had unusual antibacterial properties beyond what hydrogen peroxide could explain. The term “Unique Manuka Factor” was coined to describe this activity, and it eventually became a formal certification system managed by the UMF Honey Association (UMFHA).
Where MGO measures a single compound, UMF tests for multiple markers at once. A UMF-certified honey is checked for its MGO content, its DHA level (which indicates how much more MGO the honey will develop over time), and a compound called leptosperin that serves as a chemical fingerprint for genuine manuka nectar. The system also checks for freshness by measuring a heat-damage indicator called HMF. Fresh honey has very little HMF, while honey that’s been overheated or poorly stored accumulates it. International standards cap HMF at 40 mg/kg for most honeys.
This multi-marker approach means UMF does two jobs at once: it confirms potency and verifies that the honey actually came from manuka flowers rather than being blended or mislabeled.
How the Two Scales Line Up
Because UMF incorporates MGO as one of its markers, the two systems have a rough numerical relationship:
- MGO 83+ corresponds to UMF 5+
- MGO 100+ corresponds to UMF 6+
- MGO 250+ corresponds to UMF 10+
- MGO 400+ corresponds to UMF 13+
- MGO 550+ corresponds to UMF 16+
- MGO 700+ corresponds to UMF 18+
At the lower end (MGO 83+ / UMF 5+), the honey is mild and works fine as an everyday sweetener with modest bioactivity. Mid-range grades around MGO 250+ / UMF 10+ are typically marketed for general wellness. Higher grades like MGO 550+ / UMF 16+ and above represent very high potency and come with a significantly higher price tag.
One notable gap: some brands sell MGO 30+ honey, which is a multifloral blend containing some manuka. The UMF system does not certify blends, so you won’t find a UMF equivalent at that level.
New Zealand’s Export Standards
New Zealand’s Ministry for Primary Industries (MPI) sets a legal definition for what can be exported as manuka honey. The test requires five attributes: four specific chemical markers plus DNA from manuka pollen. Honey that meets all five at higher thresholds qualifies as monofloral manuka (made predominantly from manuka nectar). Honey that meets the attributes at lower thresholds qualifies as multifloral manuka (a mix of nectars including manuka). Honey that fails any one of the five attributes cannot be labeled manuka at all for export.
This government-level testing is separate from the UMF and MGO systems, but it works alongside them. A jar of UMF-certified manuka honey has been independently tested by the UMFHA on top of meeting MPI’s export requirements.
How to Verify What You’re Buying
If your jar carries a UMF mark, you can check its authenticity through the UMFHA’s online certification search. Every certified jar has a four-digit license number (usually on the side or back of the label) and a batch number that traces back to the exact lab test results for that production run. Entering both numbers on the UMFHA website confirms whether the honey’s bioactivity levels and quality markers were independently verified.
For MGO-only brands, there’s no single centralized verification system. You’re relying on the brand’s own testing and reputation. Some MGO brands are highly reputable and publish their lab results, but the lack of a unified third-party check is the main practical difference between the two systems from a consumer standpoint.
Which Rating System Matters More
Neither system is “better” in an absolute sense. MGO gives you a straightforward measurement of the key antibacterial compound, and it’s easy to compare across brands. UMF gives you that same potency information wrapped in a broader authenticity check that also accounts for freshness and botanical origin.
If you’re comparing two jars side by side, the most useful thing is to convert them to the same scale using the chart above. An MGO 400+ jar and a UMF 13+ jar are roughly equivalent in antibacterial strength. The choice between them comes down to whether you value the additional verification that UMF certification provides, and how much you trust the individual brand behind an MGO-only label.