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Most Sampled Colorado Cannabis Flower Lacked a Proper Expiration Date
In A Nutshell
- Only about 14%, or 1 in 7, of 480 Colorado cannabis products met all six state label requirements checked in the study.
- Flower fared worst, with 2.2% passing, compared with 31% of concentrates such as wax and shatter.
- Only about half of products carried a proper expiration date, just 16.9% had storage instructions, and THC strength was worded seven different ways.
- Researchers read labels only, with no lab testing, and read the pattern as a sign of weak oversight, which the study did not measure.
A shopper who picks up a jar of cannabis flower in Colorado will almost certainly see the state’s warning symbol on the label. Whether the label says when the buds go stale, or how to store them, is a different story. In a new analysis of 480 products, only about 14%, or roughly 1 in 7, carried all six details Colorado requires on its labels. Flower, meaning loose buds and pre-rolled joints, fared worst, with just 6 of 277 products (2.2%) passing. Concentrates, potent extracts such as wax and shatter, did better at 31%.
Colorado became the first state to legalize recreational cannabis in 2012, so labeling might seem like a settled matter by now. Missing or inaccurate expiration dates and absent storage instructions appeared to be the main reasons products failed, the authors write in the Journal of Cannabis Research.
Flower makes up the largest portion of recreational sales, the authors note, citing earlier research, so its poor record reaches a lot of buyers. Many other states also use Colorado’s rules as a model for their own programs, though earlier research shows label requirements still vary from state to state.
Colorado Cannabis Labels Often Skipped Expiration Dates and Storage Tips
A researcher working with MedPharm Holdings, a Colorado cannabis company, bought 480 products from 52 recreational dispensaries across 19 counties, aiming to cover the state broadly. The haul included 277 flower products and 203 concentrates. Researchers at the University of Colorado Boulder collaborated on the analysis.
Staff then read each label. This analysis did not lab-test what was inside, so it speaks to labeling only. Every product got a pass or fail on six items the state requires: the red THC warning symbol, a driving warning, a long-term health warning that includes pregnancy and breastfeeding, an expiration or “best by” date, storage instructions, and a statement of THC strength. The first three had to use the state’s exact wording, and a date had to follow “use by,” “best by,” or “expires.”
Labels mostly got the big warnings right. The THC symbol appeared on 99.2% of products and a THC percentage on 99%. Driving and pregnancy warnings each landed on 97.5%, a hair under the 99% bar the researchers set. Dates and storage were where labels fell apart. Only about half, 51.2%, carried a proper expiration date, and just 16.9% said how to store the product, with a line such as “Keep in a cool, dry place” counting.
Flower Labels Trailed Concentrate Labels on Dates and Storage Tips
Flower and concentrates scored about the same on the warning symbol and the two health warnings. The gap showed up on freshness. About a third of flower labels, 32.5%, had a date, compared with 76.8% of concentrates. Storage instructions were nearly absent on flower, at 3.6%, versus 35% for concentrates.
Concentrates still missed at least one requirement about 7 times in 10. That matters because their high THC levels have been linked in earlier research to a greater risk of cannabis use disorder and psychosis, the authors note.
Dates and storage tips can look like fine print, but each has a real job. THC breaks down over time, and light, heat, and moisture can weaken it or let microbes take hold, according to research the authors cite. A jar with neither leaves a buyer guessing how old it is. The study did not test why flower lags, though its sample included repackaged and deli-style flower, which may be one factor.
Cannabis Potency Labels Used Seven Phrasings
Strength wording was its own mess. Across all 480 products, THC potency appeared seven different ways, mixing “THC,” “Total THC,” and “THCA,” the raw form of THC found in the plant. Concentrates mostly said “Total THC,” while flower more often said just “THC.” Colorado’s rules call for the percentage of total THC.
That inconsistency makes comparing two products harder, and the authors say it “may create confusion about the actual strength of a product,” especially for newer or occasional users. Five products, all of them flower, listed no THC percentage at all. A shopper comparing two jars could end up weighing numbers that are not measuring quite the same thing.
Colorado Cannabis Labels Point to a Possible Oversight Gap
Pulling products with bad labels off shelves is possible. Noncompliant products can be removed or destroyed, and repeated violations can cost growers, producers, or dispensaries their licenses. Whether Colorado’s regulators have the capacity to run independent audits remains unclear, the authors write. They read the results as pointing to “inadequate regulatory oversight,” but the study did not measure inspections, staffing, or whether any shopper was harmed by a missing label.
More than a decade after legalization, most products in this sample missed at least one of Colorado’s own label rules. Stronger ongoing monitoring may help, the authors say. Until it arrives, a shopper reaching for Colorado flower is more likely than not to find no expiration date, based on this sample.
Disclaimer: This article is based on a published research paper and is intended for general information only. It is not medical or legal advice. Anyone with questions about cannabis use or its health risks should speak with a qualified healthcare professional. The study is an unedited accepted manuscript, so details may change before final publication.
Paper Notes
Limitations
Researchers reviewed labels, not what was inside the packages, so the study speaks to labeling compliance and says nothing about actual potency, freshness, or contamination. Products came from Colorado’s recreational market only, and the authors caution against applying the results to other states. Medical cannabis products and edibles were not examined. Although the sample is the largest of its kind assessed in Colorado, the authors say the size of the state’s market makes it hard to tell whether the problems are systemic or limited to certain dispensaries or regions. The work is a secondary analysis that expands on an earlier project by the same group. The paper’s text names the warning symbol as the only item to reach the expected compliance level, though its own table shows THC percentages on 99% of labels, a result the statistical test also did not flag as noncompliant. The authors’ conclusions about oversight and public health are interpretation, since the study did not measure enforcement or health outcomes.
Funding and Disclosures
Funding came from the Institute of Cannabis Research at Colorado State University Pueblo, and the projects were approved by the State of Colorado’s Medical Marijuana Scientific Advisory Council. Two authors, Tylor Savage and Duncan I. Mackie, were employees of MedPharm Holdings LLC, doing business as Bud & Mary’s, during the study period. Mackie holds a Schedule I license from the U.S. Drug Enforcement Administration. MedPharm Holdings is a Colorado-licensed cannabis research company and a bulk manufacturer of cannabis products for the state’s adult-use market, and the paper states it has no stake in any products tested in the studies reviewed by this manuscript. Mackie is also an editor for the Journal of Cannabis Research and was not involved in the journal’s review of, or decisions about, this manuscript.
Publication Details
Titled “Warning label compliance of recreationally available cannabis flower and concentrate products in the state of Colorado,” the paper was written by Grace M. MacDonald, Jonathon K. Lisano, Tylor Savage, Marco Ortiz Torres, Gregory Giordano, Duncan I. Mackie, and L. Cinnamon Bidwell. MacDonald, Giordano, Lisano, Ortiz Torres, and Bidwell are affiliated with the University of Colorado Boulder, while Savage and Mackie are affiliated with the University of Colorado Anschutz Medical Campus and MedPharm Holdings. MacDonald is the corresponding author. It was published in the Journal of Cannabis Research in 2026, as an unedited accepted manuscript (Article in Press), after acceptance on August 14, 2026, and online publication on August 28, 2026. DOI: 10.1186/s42238-026-00489-7. The analysis expands on Giordano et al. (2025), “Accuracy of labeled THC potency across flower and concentrate cannabis products,” Scientific Reports, 15(1), DOI: 10.1038/s41598-025-03854-3.
