quick summary

MGO in manuka honey can refer to two things:

  • Methylglyoxal - a compound found in manuka honey that kills bacteria.
  • The MGO rating system - a number rating given by an independent association to confirm the honey is real.

The two are connected, as the MGO rating is determined by the level of MGO found in the honey. MGO is unique to manuka honey and why it is so sought after.

MGO ratings are necessary because a lot of fake manuka honey is sold in the world today. 

However, the MGO rating is only one of several rating systems used in New Zealand (where most manuka honey is produced), and does have some limitations compared to other systems.

MGO with regards to manuka honey can mean two different things.

First, it can be an abbreviation for methylglyoxal, the name of a unique compound that is found in manuka honey which is effective at fighting bacteria.

Second, it can refer to the manuka honey rating system developed by Manuka Health in 2008, which is what you will see on many New Zealand manuka honey products.

In this article, we'll break down the meaning of both in detail.

Methylglyoxal - the antibacterial compound

When you hear about the highly-renowned antibacterial properties of manuka honey, the compound responsible is methylglyoxal (MGO).

This is a naturally occurring compound in manuka honey, and is the stuff that makes manuka honey so special and gives it many of its health benefits.

While there are other compounds that make manuka honey unique, it is MGO that provides the germ-fighting abilities, which is why this compound is most well known and most commonly measured in manuka honey testing.

The development of MGO within manuka honey actually starts with the nectar of the manuka flower, also known as leptospermum scoparium.

This nectar contains a special enzyme called dihydroxyacetone (DHA). 

When the bees collect this nectar from the manuka plant and bring it back to the hive, this DHA eventually converts itself into MGO.

While there is a complex chemical reaction that happens here during the honey-making process, all you really need to understand is that DHA over time becomes MGO.

With high DHA levels and a lot of time, the MGO level will be high.

With low DHA levels and a short time, the MGO level will be low.

A higher MGO level indicates higher potency.

While methylglyoxal isn't the only compound that gives antibacterial activity in honey, it is the one that makes manuka honey unique from other honeys.

Most honeys do offer some antibacterial effect, which comes from their naturally occurring levels of hydrogen peroxide.

Manuka honey has hydrogen peroxide too, but MGO gives it something known as NPA, or non-peroxide activity. Both the peroxide and non-peroxide activity work almost like a tag-team as a two-pronged attack on bacteria, which is what makes manuka honey so effective.

MGO levels also can indicate purity, as it can be very hard to achieve high MGO levels with a multifloral honey (made of many different nectars).

Only monofloral honeys (made of mostly manuka nectar, and therefore more pure) tend to achieve high MGO readings.

MGO - The Rating System

Manuka honey has various rating systems, and one of them is the MGO rating system developed by a company called Manuka Health in 2008.

Why does manuka honey need a rating?

Various reasons.

First - there is a lot of fake manuka honey in the world today.

New Zealand only produces around 1,500 to 2,000 tons of manuka honey each year.

However, more than 10,000 tons of "manuka honey" is sold each year. 2,000 tonnes in the UK alone.

If you do the math, that's obviously impossible! 

It's likely that 80% of manuka honey sold in the world today is not actually real.

For this reason, New Zealand established a number of rating systems and associations to give consumers confidence that they are buying real manuka honey from New Zealand.

The MGO system is a test for the MGO levels, which then results in an MGO rating.

As we said earlier, MGO is responsible for many of the germ-killing antimicrobial actions in manuka honey.

When buying a manuka honey with an MGO rating, you can be confident that your honey has been tested for certain level of methylglyoxal content, which will be marked every jar of manuka honey that has been tested via this sytem.

jar of manuka honey

Things to note about an MGO rating of manuka honey:

  • MGO is only one of several manuka honey rating systems. There is also KFactor by Wedderspoon, AMHA (Australian Manuka Honey Association) and UMF (Unique Manuka Factor) which is the most established rating. You can read more about those here.
  • The MGO level can change over time. This means the MGO level when the honey was tested and labelled may differ from the level when you buy it.
  • MGO is only one indicator of a genuine manuka honey. Others include compounds like leptosperin, dihydroxyacetone (DHA) and hydroxymethylfurfural (HMF). The UMF grading system will test for all of those.

About the author 


I'm Erin, and my family has been raising bees for over two generations. We no longer raise bees on Manuka flowers, but it remains one of our favorites, and we eat it daily, among other honeys like Kamahi and Rata. Since Manuka has grown in popularity overseas in recent years, we thought we should educate people on the true benefits of Manuka and how to find quality Manuka honey. Haere mai to our site, written by us and designed by our brilliant computer whiz of a son, Byron. We hope you find it helpful!

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