Why Cannabis Potency Results Vary Between Laboratories
It's one of the most common frustrations in the cannabis supply chain: you send what feels like the same product to two different labs, and you get back two meaningfully different potency numbers. Neither lab is necessarily wrong. Here's what's actually going on.
It's one of the most common frustrations in the cannabis supply chain: you send what feels like the same product to two different labs, and you get back two meaningfully different potency numbers. Neither lab is necessarily wrong. Here's what's actually going on.
Sampling Is Rarely Identical
No two samples pulled from the same batch are chemically identical down to the decimal point, especially with flower, where cannabinoid concentration can vary slightly across different parts of a plant or different plants within the same harvest lot. If two labs are working from two separately pulled samples — even from the same batch — some variation between results is expected before either instrument even runs.
Method Differences
Most labs use HPLC for potency testing, but the specific calibration standards, column type, and internal method validation can differ between labs, producing small but real differences in reported results. This is normal in analytical chemistry — no method is a perfect, universal ground truth, which is part of why measurement uncertainty is reported alongside results in the first place.
Calibration and Standards
Labs calibrate their instruments against reference standards, and the quality and sourcing of those standards can vary. A well-run lab recalibrates on a defined schedule and uses certified reference materials, but the exact calibration curve — and how recently it was checked — affects precision.
Measurement Uncertainty Is Real, Not a Flaw
Every potency result comes with an inherent range of uncertainty — a lab reporting 24.0% THC isn't claiming the true value is exactly 24.0000%, but that it falls within a defined range around that number. Two labs reporting 23.6% and 24.4% for the same product may both be entirely correct within their respective uncertainty ranges, even though the numbers look different at first glance.
Sample Preparation and Homogenization
How a sample is ground, mixed, or otherwise prepared before analysis affects the result. A lab with a more thorough homogenization step — ensuring the tested material genuinely represents the whole sample rather than a few unrepresentative fragments — may return a more consistent number across repeat tests, even if it differs from another lab's result.
The "Lab Shopping" Concern
It's worth naming directly: inflated potency results have been a documented concern in several legal cannabis markets, sometimes described as businesses seeking out labs known for higher numbers. A reputable, accredited lab operating under consistent, validated methods is your best protection against this — both as a business trying to report accurately, and as a buyer trying to evaluate a product honestly.
What This Means for Your Business
If you're seeing meaningfully different results between labs on a consistent basis — not an occasional small variance, but a persistent, large gap — it's worth asking both labs directly about their method, calibration schedule, and accreditation scope rather than assuming one is simply "more accurate." A transparent lab will walk you through their process rather than just defending their number.
If you'd like a second opinion or a detailed walkthrough of your own potency results, Prism Triangle is happy to discuss our methodology in detail.
This article is for general informational purposes. Always confirm current Michigan CRA requirements directly with the agency.
