Stand in front of a shelf of New Zealand mānuka honey, and the labels can look like a code. One jar says UMF 15+. Another says MGO 514+. A third shows both. The numbers are not interchangeable, and the larger figure is not automatically “better.” They describe different things.
This guide explains what each rating measures, how they relate, and what to look for on a label — without treating the grades as medical claims.
First, what is being graded?
Mānuka honey comes from the nectar of Leptospermum scoparium, a shrub native to New Zealand (and also found in parts of Australia). Not every jar labelled “mānuka” is certified the same way. Two systems dominate retail packaging:
- MGO — a lab measurement of one compound.
- UMF™ — a licensed New Zealand certification that includes that compound plus several others.
They overlap. They are not the same.
What MGO means
MGO stands for methylglyoxal. On a label, it is usually written as milligrams per kilogram of honey (mg/kg).
Example: MGO 263+ means the batch was tested at at least 263 milligrams of methylglyoxal per kilogram of honey.
Key points:
- It is a single-number chemical test, typically done by HPLC in a laboratory.
- The number is a minimum at the time of testing. The “+” means the batch met or exceeded that threshold.
- There is no single global licence body that owns “MGO” the way UMF is owned. Brands can print an MGO figure after independent testing — or, in weaker cases, with little public verification.
- Methylglyoxal is not unique to mānuka in the sense that traces can appear elsewhere. A high MGO number does not, by itself, prove New Zealand origin, floral source, or that the honey has not been heat-damaged.
MGO is useful when you want a clear, comparable concentration of one marker. It is incomplete if you also care about authenticity and handling.
What UMF means
UMF™ stands for Unique Mānuka Factor. It is a registered trademark administered by the UMF Honey Association (UMFHA) in New Zealand. Only licensed members may put the UMF mark on the pack, and each batch is supposed to be independently tested.
UMF is a four-marker grade, not a single chemical:
| Marker | Role in the UMF test |
|---|---|
| MGO (methylglyoxal) | One of the signature compounds used to set the numeric grade |
| Leptosperin | Marker associated with genuine mānuka nectar; used as an authenticity check |
| DHA (dihydroxyacetone) | Precursor that converts to MGO as honey matures; used as a shelf-life and maturity check |
| HMF (hydroxymethylfurfural) | Rises with heat and age; UMF sets a maximum so the honey has not been overheated or left too long |
UMFHA publishes minimum (and, for HMF, maximum) values for each grade. Common official thresholds include:
| UMF grade | Minimum MGO (mg/kg) | Leptosperin (mg/kg) | DHA (mg/kg) | HMF (mg/kg) |
|---|---|---|---|---|
| 5+ | 83 | >100 | 150 | <40 |
| 10+ | 261 | >150 | 250 | <40 |
| 15+ | 512 | >200 | 400 | <40 |
| 20+ | 826 | >200 | 500 | <40 |
| 25+ | 1197 | >200 | 500 | <40 |
Retail conversion charts often round these to 83 / 263 / 514 / 829 / 1122 or 1200. Treat those as approximate equivalents, not a law of nature. UMFHA itself stresses that MGO alone does not “convert into” a UMF grade, because the other three markers must also pass.
A genuine UMF jar typically carries:
- the UMF™ logo
- a grade such as 10+, 15+, 20+
- a licence number you can check against UMFHA’s member list
That licence is the practical difference between “a lab printed an MGO number” and “a New Zealand industry body licensed this batch.”
UMF vs MGO at a glance
| MGO | UMF™ | |
|---|---|---|
| What it reports | Methylglyoxal in mg/kg | A licensed grade based on four markers |
| Who governs it | No single trademark owner | UMF Honey Association (NZ) |
| Authenticity check | No (MGO can exist outside genuine mānuka) | Yes — leptosperin is part of the test |
| Freshness / heat | Not required | HMF cap; DHA minimum |
| Typical label | MGO 100+, 263+, 550+, 830+ | UMF 5+, 10+, 15+, 20+, 25+ |
| Can a jar have both? | Yes — many licensed brands print both | Yes |
You cannot compare the raw numbers. MGO 263 is not “stronger than UMF 20” because 263 is larger than 20. UMF 20+ sits around MGO 826+.
Why two systems exist
Historically, mānuka was graded by a laboratory assay of non-peroxide activity (NPA) compared with a phenol standard. Those NPA numbers became the early UMF scale (UMF 10+ ≈ NPA 10, and so on).
Once chemists identified methylglyoxal as the compound behind much of that assay result, brands could print a direct mg/kg figure. MGO labels spread quickly because the number is simple. UMF stayed as a certification wrapper: same underlying chemistry, plus origin and quality checks, plus a licence.
New Zealand’s Ministry for Primary Industries also has a scientific definition of mānuka honey for export (chemical and DNA markers). UMF sits on top of that government identity test for members who want a published grade.
A note on flavour and texture
As marker levels rise, many people find the taste more intense — darker, more mineral or medicinal, less purely floral-sweet. That is a sensory observation, not a quality score. Lower-grade mānuka is still mānuka if it meets the relevant identity tests; it is simply a different chemical profile and usually a milder eating honey.
Short takeaway
- MGO = how much methylglyoxal was measured, in mg/kg.
- UMF = a New Zealand licence that requires that MGO level, leptosperin, DHA, and a low HMF result.
- The systems are related because UMF grades are built around MGO thresholds. They are not the same stamp.
- Read the units, check for a licence when UMF is claimed, and ignore the temptation to treat the bigger printed integer as the winner.
That is the whole alphabet on the lid: one number is a compound, the other is a certified bundle of tests.