Allicin mg vs mcg trips up more comparisons than almost any other unit pair, because one milligram equals 1,000 micrograms and a label can print either one without signalling the switch. A product showing 5,000 mcg and another showing 5 mg are describing the same quantity. Read them as different and you'll draw the wrong conclusion about which bottle is stronger.
Conversion first, then comparison. It's a two second step that prevents an expensive mistake.
The allicin unit arithmetic, once and properly
Move the decimal point three places. So 100 mcg is 0.1 mg, and 2,500 mcg is 2.5 mg. Fresh crushed garlic yields roughly 2.5 to 4.5 mg of allicin per gram of clove, though that figure collapses within minutes as the compound degrades, which is why almost no supplement lists allicin as a delivered amount. Aged garlic extract is standardized instead on S-allyl cysteine, typically about 1.2 mg per 600 mg capsule, and garlic powder products are often standardized on alliin rather than allicin because alliin is stable and measurable. Three different marker compounds across three formats, each in its own unit range.
Why IU shows up next to the figures
International units describe biological activity rather than weight, so they don't convert to milligrams by a fixed factor. They exist for vitamins and a few other substances where the effect per microgram varies by form. For garlic preparations IU is uncommon, but you'll meet it on vitamin lines further down the same panel, and the same rule applies: you can't compare an IU figure to a milligram figure without the specific conversion for that nutrient. Treat any label that mixes the two as one that needs a question asked.
Comparing two bottles without a calculator
Bring both to a common unit, then divide by servings. If one bottle offers 3,000 mcg per serving at two capsules daily and another offers 6 mg per serving at one capsule daily, the second is 6,000 mcg in a single capsule, twice the delivered amount at half the capsule count. On a per-serving basis the second is roughly four times stronger per capsule. That's the entire comparison, and it took less time than reading the front label twice.
What to do when the units are mixed on one label
Write the numbers down in a single unit before you decide anything. Micrograms for everything small keeps the figures readable and avoids decimals in your head. Then check the serving size, because a per-capsule figure and a per-serving figure are different questions, and only one of them tells you what a day of use costs. If a brand still won't state amounts in a convertible form, the panel is asking you to take strength on faith. Allicin and its markers are cheap to assay, so there's little reason for a maker to hide the number unless the number is unflattering.
Keep a note in your phone with the three garlic markers written out in micrograms, so the next time you're comparing two bottles in a shop you're doing one arithmetic step rather than three. Alliin, allicin and S-allyl cysteine don't convert into each other by a fixed factor, because each measures a different point in the same chemical story and the plant's own conversion efficiency varies by process. That's the honest limit of what a unit conversion can do for you here. What it can do is stop you rejecting a strong product because its number looked small in a column, and that mistake is common enough to be worth a two second habit every single time you shop.
Frequently asked questions
What is the difference between mg and mcg?Show answerHide answer
A microgram is a thousandth of a milligram, so the number looks much larger.
Why do some labels use IU?Show answerHide answer
Older units like IU describe biological activity rather than weight.
How do I compare across units?Show answerHide answer
Convert to the same unit first, then compare per serving.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
