MGO stands for methylglyoxal, a naturally occurring compound found in high concentrations in manuka honey. It’s the primary reason manuka honey has stronger antibacterial properties than regular honey, and the MGO number on a jar tells you how much of this compound is present, measured in milligrams per kilogram. The higher the number, the more potent the honey.
How MGO Forms in Manuka Honey
Methylglyoxal doesn’t start out in honey. It begins as a different compound called dihydroxyacetone (DHA), a three-carbon sugar that accumulates in unusually high amounts in the nectar of the manuka tree (native to New Zealand and parts of Australia). Once bees collect the nectar and it becomes honey, DHA slowly converts into MGO through a chemical reaction driven by the water naturally present in the honey.
This conversion happens gradually during storage and ripening. Honey producers sometimes store manuka honey in drums for months or even years specifically to allow more DHA to convert into MGO, which increases the honey’s potency over time. Warm storage conditions speed up the process. This is why a jar of manuka honey can test higher for MGO months after harvest than it did initially.
What MGO Does to Bacteria
All honey has some antibacterial activity, mostly from hydrogen peroxide produced by an enzyme bees add to nectar. MGO gives manuka honey an additional, separate mechanism. It’s a reactive compound that directly damages bacterial cells, making it effective against pathogens that other honeys can’t touch.
Research published in PLOS ONE found that when MGO was neutralized in manuka honey, its effectiveness against MRSA (methicillin-resistant Staphylococcus aureus) dropped to the same level as plain sugar water. That confirmed MGO as the key active ingredient responsible for manuka honey’s potency against this notoriously drug-resistant bacterium. MGO also showed strong activity against other staph bacteria, though it was less effective against certain gram-negative bacteria like E. coli. Even with MGO neutralized, manuka honey retained some antibacterial activity from other, still-unidentified compounds.
What the MGO Numbers Mean
When you see “MGO 100+” or “MGO 400+” on a jar, that number tells you the minimum concentration of methylglyoxal in milligrams per kilogram. Here’s how to read the scale:
- MGO 83+ corresponds roughly to UMF 5+, the entry level for manuka honey
- MGO 261+ corresponds roughly to UMF 10+
- MGO 512+ corresponds roughly to UMF 15+
- MGO 826+ corresponds roughly to UMF 20+
- MGO 1197+ corresponds roughly to UMF 25+, the highest tier
Honeys graded at MGO 260 and above are generally considered to have the minimum activity necessary for medicinal use. Below that, you’re getting a quality table honey with mild bioactive properties but not enough MGO to rely on for therapeutic purposes.
MGO vs. UMF
You’ll often see both MGO and UMF (Unique Manuka Factor) ratings on manuka honey. They’re related but not interchangeable. MGO measures just one compound. UMF is a broader grading system developed by the UMF Honey Association in New Zealand that tests for four signature compounds: MGO, DHA, leptosperin, and HMF. Leptosperin confirms the honey actually came from manuka flowers, while DHA indicates future MGO potential. So UMF functions as both a potency rating and an authenticity check, while MGO tells you only about the methylglyoxal concentration.
Evidence for Wound Healing
The most robust evidence for high-MGO honey involves wound care. Medical-grade manuka honey products (typically rated MGO 400+) are used in clinical wound dressings. In a study using a porcine burn model, wounds treated with manuka honey dressings had a 54% reepithelialization rate by day 7, compared to 31% in the control group. By day 10, that gap widened to 85% versus 72%. By the end of the study, all manuka-treated wounds had achieved complete healing, with significantly thicker new skin formation at every time point measured.
These results reflect medical-grade honey applied directly to wounds under controlled conditions, not eating honey from a jar. The topical antibacterial effect of MGO, combined with honey’s natural acidity (around pH 3.5) and moisture-regulating properties, creates an environment that both fights infection and supports tissue repair.
How Heat and Storage Affect MGO
MGO levels in manuka honey are relatively stable under normal conditions, but high heat breaks them down. Heating honey to 90°C (194°F) for one to two hours causes measurable MGO loss. The compound reacts with amino acids naturally present in the honey, essentially getting used up in chemical reactions that produce different compounds entirely.
This matters for how you use manuka honey at home. Stirring it into boiling water, cooking with it, or leaving it in a hot car can reduce the very compound you’re paying a premium for. Room temperature storage preserves MGO content well. Gentle warming is fine, but sustained high heat is not.
On the other end of the spectrum, moderate warmth during storage actually helps, because it accelerates the conversion of remaining DHA into MGO. A jar stored at cool room temperature for several months may test slightly higher in MGO than when you bought it.
MGO Honey and Blood Sugar
Despite its bioactive properties, manuka honey is still honey. It contains roughly the same amount of sugar as any other honey, with a glycemic index around 50 (lower than table sugar at 80, but still a meaningful source of carbohydrates). High MGO content doesn’t change the sugar composition. If you’re managing blood sugar levels, manuka honey will raise your glucose in much the same way regular honey does. The MGO rating has no bearing on glycemic impact.
Choosing the Right MGO Level
If you’re buying manuka honey as a premium food product for everyday use, MGO 100 to 250 is a reasonable range that balances cost and mild bioactive benefit. For topical use on minor cuts or skin concerns, MGO 400+ offers meaningfully higher antibacterial potency. Anything above MGO 800 is at the top of the market in both concentration and price, and most people won’t notice a practical difference between MGO 800 and MGO 1200 for general wellness purposes.
The price jumps between tiers can be steep. A jar of MGO 100+ might cost $20 to $30, while MGO 800+ can run $80 or more for the same size. Whether the higher concentration is worth it depends entirely on what you’re using it for. For toast, lower grades are fine. For a targeted antibacterial application, the higher ratings carry more of the compound that makes manuka honey unique in the first place.