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Manuka honey grading: UMF, MGO and what the numbers mean

Manuka is sold on numbers that most buyers cannot interpret and that several sellers would rather they did not. Here is what each system measures, which ones are audited, and what a high number does and does not buy.

Buying and storingReviewed 2026-08-02

What the number is measuring

Mānuka nectar contains dihydroxyacetone, or DHA. Over weeks and months in the jar, DHA converts non-enzymatically into methylglyoxal, or MGO — a compound with demonstrable antibacterial activity in laboratory conditions and one that most honeys contain only in trace amounts. Manuka's entire premium rests on this single conversion, and it is why manuka is the one honey whose rating rises during storage while everything else about it slowly degrades.

This matters because it makes manuka genuinely unusual rather than merely well marketed. Most honey's antibacterial activity comes from hydrogen peroxide generated when the honey is diluted, and that activity is destroyed by catalase — an enzyme present in human tissue and blood. Manuka's methylglyoxal activity is not peroxide-dependent, so it survives conditions that abolish an ordinary honey's. That is a real chemical distinction. What follows from it clinically is a much narrower question, and one the numbers on the jar do not answer.

The competing rating systems

Manuka rating systems and what each one actually certifies
SystemWhat it measuresIndependently audited?
MGOMethylglyoxal concentration in milligrams per kilogram. A direct chemical measurement.Depends on the packer. The measurement is objective; whether anyone verified it is a separate question.
UMFA graded rating from a licensing body, testing four chemical markers including methylglyoxal, leptosperin and DHA, plus authenticity.Yes — licensed, audited and traceable to a licence number you can check.
New Zealand government definitionA regulatory test of four chemical markers plus a mānuka DNA marker, required for export labelling as mānuka.Yes, and it is a floor rather than a grade — it certifies the honey is mānuka, not how strong it is.
K Factor, Bio Active, Active, and similarProprietary or unspecified. Some describe pollen counts, some total activity, some nothing verifiable.Generally not. Treat an unexplained number as marketing until the seller explains what it measures.

What a high number buys, and what it does not

A high, audited rating buys you a verified concentration of methylglyoxal in a verified mānuka honey. That is worth something if you specifically want that compound. It does not buy a proportionally better food, a proportionally stronger effect, or any established clinical benefit from eating it.

The one context where medical-grade honey genuinely has established use is wound care, and it is worth being precise about what that involves: sterilised, gamma-irradiated, regulated medical products applied topically to a wound under clinical supervision. That is a different substance in a different context from a jar on a kitchen shelf, and the evidence for it does not transfer to swallowing a spoonful.

How to buy without being had

  1. Prefer a UMF licence number or a government-compliant export label over an unexplained proprietary number.
  2. Check that the number is defined somewhere on the jar or the seller's site. A number with no stated units and no stated test is not information.
  3. Be sceptical of very high ratings at low prices. More manuka is sold worldwide than New Zealand produces, and that gap is filled somehow.
  4. Ignore 'Active' and similar words used alone. They have no agreed meaning.
  5. Buy the lowest rating that meets your actual purpose, which for most people is a distinctive honey to eat.

The claims on this page

Every substantive claim is placed on a tier, and the top two tiers must also state what they are not claiming.

Emerging research

Real studies exist and point somewhere, but they are small, in vitro, in animals, or not yet replicated. Direction is not the same as a result.

Emerging research

Manuka honey's methylglyoxal content gives it non-peroxide antibacterial activity in the laboratory.

Methylglyoxal is well characterised as the compound responsible for manuka's non-peroxide antibacterial activity, and the relationship between dihydroxyacetone in the nectar, methylglyoxal in the matured honey and measured in-vitro activity is consistent and reproducible.

What this does not claim: This is laboratory activity against organisms in a dish. It is not evidence that eating manuka honey treats or prevents infection, that a higher rating produces a proportionally greater effect in a person, or that any oral benefit exists at all. The established medical use of honey is topical, on wounds, using sterilised regulated products under clinical supervision — a different context that does not transfer to a kitchen jar.

  • Identification of methylglyoxal as the dominant antibacterial constituent of manuka honey — Molecular Nutrition and Food Research / Carbohydrate Research (2008) · Peer-reviewed article
  • UMF grading and the New Zealand manuka honey definition — UMF Honey Association / New Zealand Ministry for Primary Industries · Industry body

Commonly claimed, but not supported

Widely repeated and not supported by current evidence. Listed so the correction is here rather than only the claim.

Commonly claimed, but not supported

A higher UMF or MGO rating means a healthier honey.

The rating measures a chemical concentration, and no clinical evidence links a higher rating to a greater benefit from eating the honey. Price scales far faster than the rating does, and neither is tied to a demonstrated health outcome.

  • HoneyHQ editorial synthesis — HEKNO Ltd · HoneyHQ synthesis

Sources

  • UMF grading and the New Zealand manuka honey definition — UMF Honey Association / New Zealand Ministry for Primary Industries · Industry body
  • Identification of methylglyoxal as the dominant antibacterial constituent of manuka honey — Molecular Nutrition and Food Research / Carbohydrate Research (2008) · Peer-reviewed article
  • Analytical approaches to honey authentication — Peer-reviewed food-analysis literature · Peer-reviewed article
  • HoneyHQ editorial synthesis — HEKNO Ltd · HoneyHQ synthesis

How sources are selected and weighted is set out in the sources and evidence policy.

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