It’s Friday afternoon and you’re leaving work early. You’re ready to ease into the weekend slowly and steadily, opting for mindful relaxation over nihilistic raging. Instead of heading over to a happy hour, you decide to unwind with some cannabis.
You want enough for the whole weekend. Knowing from experience, at least one other person (who never seems to have any of their own) will ask you to share. So, while your housemate or partner heads into the shop for a bottle of wine or a six-pack, you dip into the dispensary or text your plug and ask for something with “between three and five units of cannabis.” Your perfectly reasonable request is greeted with confusion and derision, because—duh!—no such thing exists.
Misunderstood or vilified when it’s not prohibited, marijuana has long suffered from a lack of concrete knowledge. One metric that experts agree is holding cannabis back is an agreed-upon “standardized marijuana unit.” Most everything else humans put in their bodies that governments regulate and tax can be easily measured, categorized and divided: a “thousand-calorie burger,” a tropical cocktail with the total alcohol equivalent of “two drinks,” movie-theater popcorn with “two servings” of butter.
But cannabis isn’t this. A host of factors, including personal tolerance and method of ingestion, as well as complications such as terpenes and secondary cannabinoids, complicate the effects of cannabis and defy easy standardization.
If a five-milligram edible hits two people differently, and five milligrams of THC inhaled hits an entirely different way from the edible, what’s the purpose of printing “five milligrams” on the label in the first place? You could be forgiven for declaring the whole exercise futile, except that’s not how science or regulators work.
“Consensus regarding a standardized cannabis unit is of utmost importance to accelerate research in medical cannabis and enable safe and effective use of cannabis products,” as a research team led by Joshua Brown, a professor of pharmaceutical outcomes and policy at the University of Florida, wrote in a recent article published in the journal Medical Cannabis and Cannabinoids.
But rather than propose one, Brown and his colleagues poured cold water on the concept.
“However, it is unlikely that a “one size fits all” definition will capture both nonmedical and medical use of cannabis and may be insufficient for constructing comparisons between administration routes,” the article stated.
Rule of Fives
So far, the “best available” standardized cannabis unit seems to be 5 milligrams of THC, or about half of the 10-milligram dose that regulators in adult-use states including California and Colorado have hit upon. Adult-use edibles in those states are limited to no more than 100 milligrams per packaged product, and regulations require the 100-milligrams to be broken up into discreet units, with the idea that such careful division will reduce instances of over-intoxication.
Five milligrams of THC per “marijuana unit” is the standard first proposed in 2020 by researchers Tom Freeman and Valentina Lorenzetti, who published their reasoning in the journal Addiction, arguing that such a value reflects “the quantity of primary active pharmacological constituents.”
With concentrates that isolate THC from other constituent compounds such as secondary cannabinoids and terpenes—edibles or pharmaceutical-grade cannabis products including FDA-approved Sativex—the “rule of 5” is probably workable, cannabis industry insiders say, but with exceptions that quickly saddle the “standard” with so many qualifications that it’s no longer standard.
“The problem with five milligrams is, how do you get five milligrams in your lungs versus your stomach?” said Mark Lewis who holds a doctorate degree in biochemistry and is the president of Napro Research, a California-based analytics firm. Five milligrams inhaled will hit more quickly than five milligrams ingested, which both hits more slowly and is metabolized differently by the liver. Any “standard unit” must address questions of bioavailability, the amount of cannabis a person can metabolize over a period of time.
For all these reasons, “five milligrams isn’t five milligrams, isn’t five milligrams,” he said.
Lewis highlighted some of the most basic impediments to a five-milligram standard: Beyond method of ingestion, there’s secondary cannabinoids including CBD as well as THC-V and terpenes, all of which can help “10 milligrams” hit more quickly or more intensely than 20—a phenomenon he experienced firsthand when trying out a new hemp-derived, Delta-9 THC-based gummy.
The gummy had five milligrams of THC advertised—a small dose, a microdose for Lewis. However, the gummy also had 2-3% essential oils. “I took one in the morning, and—oof! It snuck up on me,” he said. “I was driving, and thought, ‘Wow, that coffee was strong—I’m talking about conspiracy theories and some weird stuff.’ Then I remembered I ate that gummy. And I was pretty dang buzzed for the next couple of hours.”
Other product-makers question whether a standard unit is more necessary than accurate labeling, whatever the unit may be.
“I think the accuracy of the label is more important than the standard,” said Ian Monat, the co-founder and CEO of rhythm, which makes hemp-based CBD beverages. Monat said that CBD products in particular are beset with wildly inaccurate labels. And even a precise figure can become inaccurate over time as cannabinoids degrade, processes that are accelerated in the presence of compounds including aluminum—like a beverage can.
Brown and his co-authors agree. In their article, they call for standardized units to somehow accommodate questions of ingestion as well as CBD ratios and essential oils, and state that patients need to be clearly informed that their product’s concentration and the “delivered dose” may be different—and, like Lewis said, that five milligrams isn’t always five milligrams.
Or, in another analysis, outside of THC-only pharmaceutical grade cannabis or strictly-THC-only extracts or edibles, dosage is too complicated and too personal a question to be answerable in universal figures.