What Manuka Honey Is Best: UMF, MGO, and Authenticity

The “best” manuka honey is the one with the highest verified concentration of methylglyoxal (MGO), the compound responsible for its unusual antibacterial strength. Both the UMF (Unique Manuka Factor) and MGO grading systems track this same compound, just from different angles, so a jar rated UMF 15+ and one rated MGO 514 are telling you roughly the same thing. But the grading number is only useful if the honey inside the jar is actually genuine manuka, and that turns out to be a harder problem than most buyers realize.

Why MGO Is the Compound That Matters

Most honeys owe their germ-killing properties to hydrogen peroxide, which is produced by an enzyme bees add during processing. Manuka honey is different. Researchers identified methylglyoxal as its dominant antibacterial compound, showing that manuka samples remained effective against bacteria even when diluted to concentrations of about 15 to 30 percent, far below the threshold where other honeys lose their punch.¹ In an interesting twist, MGO at high levels actually suppresses hydrogen peroxide production in manuka honey by interfering with the enzyme that generates it, so the two antibacterial pathways work against each other rather than together.² This means manuka’s antibacterial power comes almost entirely from MGO, making the concentration of that single molecule the most useful measure of quality.

MGO doesn’t arrive in the honey ready-made. Bees foraging on Leptospermum scoparium (the manuka bush) collect nectar that is rich in dihydroxyacetone (DHA), a sugar-like compound. Over time, DHA slowly converts into MGO. Freshly harvested manuka honey contains low levels of MGO and high levels of DHA; as the honey matures during storage, DHA drops and MGO rises.³ This conversion happens faster at warmer temperatures and is sensitive to the honey’s moisture content. Even a small increase in water content can accelerate the reaction significantly.⁴ This is why newly extracted manuka honey often tests lower than the same batch tested months later: the MGO is still forming.

UMF and MGO Ratings, Decoded

Walk into a health food store and you’ll see two competing label systems. Understanding what each one measures makes comparison shopping far simpler.

The MGO rating is straightforward. A jar labeled MGO 100 contains at least 100 milligrams of methylglyoxal per kilogram of honey. MGO 250 means at least 250 mg/kg, and so on up through MGO 550, 800, and beyond. Higher number, more MGO, stronger antibacterial activity. If you’re buying manuka primarily for its antimicrobial properties, the MGO number gives you the most direct read on what you’re getting.

UMF (Unique Manuka Factor) is a broader grading system managed by the UMF Honey Association, a New Zealand industry group. It started as a measure of antibacterial activity compared to the antiseptic phenol, but it has evolved into a composite test. A UMF-certified honey must meet thresholds for MGO, DHA (the precursor compound), and leptosperin (a chemical marker specific to manuka nectar). The UMF number roughly maps onto an MGO concentration: UMF 5+ corresponds to about MGO 83, UMF 10+ to roughly MGO 263, UMF 15+ to about MGO 514, and UMF 20+ to around MGO 829. Because UMF includes the leptosperin test, it doubles as a partial authenticity check, which plain MGO ratings don’t do on their own.

For practical purposes, the two systems are measuring the same core quality. A UMF 10+ jar and an MGO 263 jar should perform similarly. The question is whether you trust the certification body behind the label, and whether the honey is genuine in the first place.

How to Know the Honey Is Actually Manuka

Authenticity is the biggest unresolved problem in the manuka honey market. New Zealand produces a limited volume of genuine manuka honey each year, yet the amount sold globally far exceeds that figure. Some of the discrepancy is accounted for by blending: mixing small amounts of real manuka with cheaper honeys to produce a jar that tests at a low MGO level. Some is outright fraud, where synthetic MGO is added to non-manuka honey, or where closely related honeys are sold under the manuka name.

The conventional tool for identifying a honey’s floral origin is pollen analysis, but this doesn’t work well for manuka. The pollen of Leptospermum scoparium (manuka) looks nearly identical under a microscope to the pollen of Kunzea ericoides (kānuka), a closely related species whose honey lacks the high MGO levels that make manuka valuable.⁵ Standard tests like flavor assessment, color, and conductivity measurements also can’t reliably distinguish the two.

This is where chemical markers come in. Leptosperin, a compound formally called methyl syringate 4-O-β-d-gentiobioside, has been identified specifically in manuka honey and remains relatively stable during storage, making it a useful authentication marker.⁶⁷ Another compound, lepteridine, has shown promise as a screening tool when measured alone or alongside leptosperin.⁸ New Zealand’s government adopted a regulatory definition of manuka honey in 2017 that requires testing for a panel of chemical markers including leptosperin, along with a DNA test for Leptospermum scoparium pollen. This regulatory framework is the strongest safeguard currently available, but it only applies to honey exported from New Zealand. Manuka-labeled products from other countries or sold through informal channels may not undergo the same scrutiny.

As a practical rule for buyers: look for jars with either a UMF certification mark (which includes leptosperin testing) or a New Zealand export-certified label. A jar that displays only an MGO number without any independent certification is harder to verify, because synthetic MGO can be added to any honey.

What the Clinical Evidence Shows for Wound Care

Wound healing is the area where manuka honey has the strongest track record. Medical-grade manuka honey products are already used in clinical wound care in many countries, applied as impregnated dressings for burns, surgical wounds, and chronic ulcers. An evidence-based review found that manuka honey demonstrates broad-spectrum antimicrobial and antibiofilm effects, supports non-traumatic debridement (the removal of dead tissue), and modulates inflammation to promote tissue regrowth. Clinical studies reported reduced bacterial load, faster healing, and improved patient comfort in both surgical and chronic wounds.⁹ A retrospective study of chronic nonhealing wounds found that manuka honey dressings promoted tissue growth, suppressed inflammation, and accelerated debridement.¹⁰

For wound care specifically, MGO concentration matters because it directly determines antibacterial strength. Medical-grade manuka products typically have a minimum activity rating equivalent to UMF 12+ or higher (roughly MGO 356+). Lower-rated honeys may still have general soothing properties, but the antibacterial punch drops off. If you’re choosing manuka specifically for dressing a wound, the higher-activity grades are the point.

Gut Health and the Helicobacter pylori Question

One of the more interesting research threads involves manuka honey against Helicobacter pylori, the bacterium that causes most stomach ulcers. Lab studies going back to the 1990s showed that a 5 percent solution of manuka honey completely prevented visible growth of H. pylori isolates, while a 40 percent solution of conventional honey (whose activity relies on hydrogen peroxide) had no effect.¹¹ More recent work using animal models found that manuka honey produced inhibition zones comparable to conventional medications, and that treated animals showed reduced stomach bacterial loads, improved tissue condition, and lower levels of inflammation markers.¹²

The gap, as with many natural remedies, is between lab results and human clinical trials. In a test tube, manuka honey reliably kills H. pylori. In a living stomach, the honey gets diluted by gastric fluids and doesn’t stay in contact with the bacterial colonies for long. No large randomized controlled trial has yet shown that eating manuka honey eradicates H. pylori infections in people. It remains a promising complementary approach, not a replacement for antibiotic-based eradication therapy.

Oral Health Benefits and Caveats

There’s a common claim that manuka honey is good for your teeth and gums, which is partly true and partly misleading. Research shows that manuka honey can reduce dental plaque bacteria and inhibit the acid production that contributes to plaque formation.¹³ A clinical study found that using manuka honey over 21 days significantly reduced S. mutans counts (the main cavity-causing bacterium) by about 76 percent.¹⁴ The gram-negative bacteria associated with gum disease are particularly sensitive to medical-grade manuka honey.

Here’s the catch. S. mutans, the cavity-causing species, is relatively resistant compared to the gum-disease bacteria. Honey is full of fermentable sugars, and its low pH can directly demineralize tooth enamel. Researchers studying periodontal applications concluded that these factors work against using manuka honey as a sustained oral treatment, despite its antimicrobial properties.¹⁵ In short, the antimicrobial effect is real, but honey’s sugar and acid content create a tradeoff that makes it a poor substitute for conventional oral hygiene products.

How Storage and Heat Affect Quality

If you’ve spent good money on high-MGO manuka honey, how you store it matters. MGO is reactive: when honey is heated, MGO binds to amino acids naturally present in the honey and gets consumed in chemical reactions. Heating at 90°C caused significant drops in MGO, with the compound reacting with amino acid derivatives to form new byproducts.¹⁶ This means stirring manuka honey into boiling tea or using it in baking will degrade the very compound you paid a premium for.

Room temperature storage is fine and even beneficial in one respect: as noted earlier, the DHA-to-MGO conversion continues slowly at ambient temperatures, so a jar can actually become more potent over months of storage. But the conversion also produces hydroxymethylfurfural (HMF) as a side product, and HMF levels increase with both time and temperature.¹⁷ HMF isn’t dangerous at the levels found in honey, but elevated HMF is used by regulators as a marker of overheating or age degradation, and very high levels could technically move a jar outside specification. The practical takeaway: store manuka honey in a cool, dark place. Use it at room temperature or add it to drinks that have cooled below scalding. Don’t cook with it if you want the antibacterial benefits intact.

Why Two Jars From Different Sites Can Differ So Much

One of the less appreciated aspects of manuka honey quality is how dramatically MGO levels vary depending on where the bees are foraging. A study examining manuka honey from multiple New Zealand sites found that MGO concentrations at one site were 89 to 245 percent higher than at the other sites studied. Soil chemistry played a role: the only soil factor that correlated with honey MGO was soil nitrate levels, and several mineral concentrations in the honey (manganese, copper, magnesium, and others) were negatively correlated with MGO.¹⁸ This means that even within New Zealand, the same species of manuka bush growing in different soil conditions can produce nectar with vastly different DHA levels, and therefore honey with vastly different MGO potential.

This site-to-site variation is one reason why premium manuka producers guard their apiary locations carefully and why blending practices are common. A producer might blend high-MGO honey from one region with lower-MGO honey from another to achieve consistent target grades across their product line. It also explains why “wildcrafted” or single-origin manuka honey commands higher prices when it tests at high MGO levels: the geographic luck of the soil and the plants growing in it is doing a lot of the work.

Australian Leptospermum Honey as an Alternative

New Zealand doesn’t have a monopoly on the Leptospermum genus. Several Leptospermum species grow natively in Australia, and some produce honey with DHA and MGO levels comparable to or even higher than New Zealand manuka.¹⁹ This has sparked a long-running trade dispute between the two countries over who gets to use the word “manuka.” Australian producers argue that their Leptospermum honeys have similar chemical profiles and antibacterial performance, while New Zealand has pushed to trademark the term exclusively.

For buyers, the chemistry doesn’t care about the trademark dispute. If an Australian jelly bush or tea tree honey tests at high MGO levels and is properly certified, it should perform comparably. The challenge is that Australian Leptospermum honey doesn’t yet have as established a certification infrastructure as New Zealand’s UMF system, so verifying claims can be harder. As the Australian industry matures and develops its own grading standards, these honeys are likely to become more widely available and more reliably labeled.

A Caution for Diabetic Wound Care

The one area where more MGO might not be better involves diabetic ulcers. Methylglyoxal is a potent protein-glycating agent, meaning it reacts with and damages proteins in ways that produce advanced glycation end products (AGEs). AGEs play a role in the impaired wound healing characteristic of diabetes, and the concentrations of MGO in manuka honey are up to 100-fold higher than in conventional honeys.²⁰ This raises a genuine concern: the same compound that gives manuka its antibacterial advantage could theoretically delay healing in people whose wounds are already impaired by glycation-related damage.

This doesn’t mean manuka honey is dangerous for people with diabetes. Medical-grade manuka products are used on diabetic wounds in clinical settings, and many clinicians report positive outcomes. But the theoretical concern is well-founded enough that if you’re managing a diabetic ulcer at home, you should involve your healthcare provider rather than self-treating with high-MGO honey. The standard wound-care evidence, which is strong, was mostly generated in non-diabetic populations, and the specific interaction between exogenous MGO and diabetic tissue biology hasn’t been fully resolved.

Practical Guide to Choosing a Jar

Pulling the threads together into buying decisions:

For general use: MGO 100+ or UMF 5+ is sufficient if you’re using manuka as a premium table honey with mild antibacterial properties. You’ll get some MGO benefit without the steep price of higher grades.
For targeted antibacterial use: MGO 250+ or UMF 10+ is a reasonable starting point. Clinical wound-care products typically use activity levels equivalent to UMF 12+ or higher.
For wound dressing: Use only medical-grade, gamma-irradiated manuka honey products designed for wound contact. Don’t apply grocery-store honey to open wounds, no matter how high the MGO rating. Medical-grade products are sterilized in a way that preserves MGO activity.
For authentication confidence: Choose jars with UMF certification (which tests for leptosperin and DHA alongside MGO) or New Zealand government export certification. A standalone MGO number without third-party verification is easier to fake.
For storage: Keep the jar sealed, out of direct sunlight, at room temperature. Avoid heating above about 40°C if you want to preserve the MGO content.

The MGO rating is the single most informative number on the jar, but only when backed by credible certification. A verified MGO 263 (UMF 10+) jar from a certified New Zealand producer will reliably deliver what the label promises. An uncertified jar claiming MGO 800 from an unknown source is a gamble. In this market, provenance and certification matter at least as much as the number on the front.