Cannabis Flower Labels Consistently Overstated THC Content Compared to Independent Testing | Research

The takeaway

Independent testing of 74 cannabis products from licensed Colorado dispensaries found that flower product labels significantly overstated THC content, with some falling outside the legally allowed 15% variance.

Cannabis consumers who use label information to guide purchases and policymakers working on cannabis regulations.

Flower THC labels were significantly inflated beyond the 15% legally allowed variance

What the researchers found

Overall, label values were significantly higher than tested values for flower and edible products (p<0.001), but not for concentrates (p=0.85). Flower products were significantly lower than labels even accounting for the 15% legal variance (p=0.04). Concentrates and edibles fell within legally allowable ranges.

Why it matters

Consumers often choose cannabis products based on labeled THC percentages. If flower labels systematically overstate potency, consumers may be making purchasing decisions based on inaccurate information, and paying more for products marketed as "higher potency."

The numbers in context

74 products tested from licensed Colorado dispensaries. Flower labels significantly overstated THC (p<0.001) and exceeded the 15% legal variance (p=0.04). Concentrate labels were accurate (p=0.85). Edible labels overstated THC (p<0.001) but within legal variance (p=0.5).

How the study worked

Observational study collecting cannabis samples from a larger impairment study. 74 flower, concentrate, and edible products purchased from licensed Colorado dispensaries were independently tested for THC concentration and compared to label claims.

What this study cannot tell us

Small sample size (74 products). Products came from one geographic area (Denver metro). Voluntary donation of samples may introduce selection bias. Testing methodology differences between labs could account for some variance.

How to read the evidence

Preliminary: small observational study from one region with voluntary sample donation, though findings align with broader industry concerns.

When this study was published

2025 preprint (medRxiv).

The bigger picture

THC potency inflation on labels has been suspected in the cannabis industry. This independent testing confirms the problem exists, particularly for flower products, and raises questions about testing lab practices and regulatory enforcement.

Questions still open

Are testing labs incentivized to report higher THC values? How widespread is label inflation across other legal cannabis markets? Should regulators require more stringent testing standards?

Common questions

Were all cannabis product types equally inaccurate?

No. Flower products had the worst label accuracy, significantly overstating THC beyond legal limits. Concentrates were the most accurate. Edibles overstated but stayed within legal variance.

Why would labels overstate THC?

Higher THC percentages may drive sales and higher prices. There are concerns about testing lab practices and insufficient regulatory oversight of accuracy standards.

Read the original research

Commercial Cannabis Product Testing: Fidelity to Labels and Regulations.

medRxiv : the preprint server for health sciences

View on PubMed ↗Publisher’s paper ↗

Citation

Limbacher, Sarah; Godbole, Suneeta; Wrobel, Julia; Mackie, Duncan I; Goldman, Stephen; Brooks-Russell, Ashley. (2025). Commercial Cannabis Product Testing: Fidelity to Labels and Regulations.. medRxiv : the preprint server for health sciences. https://doi.org/10.1101/2025.03.14.25323943