How Accurate are THC Potency Tests?

In 2011 two cannabis organizations challenged 10 labs to test 6 of the same cannabis samples for THC potency. The results of the Ring Test revealed that testing procedures were far from standardized, or perfect for that matter. The majority of labs produced results that deviated within 20% of each other.

While that’s considered a “normal” variation, the ideal deviation would be no more than 15%. But three of the labs produced results that were far from normal, deviating by 25%+ on more than half of the samples.

This indicated glaring accuracy errors, which are still common today. Such discrepancies are unacceptable for cannabis patients and consumers who rely on accurate potency measures to take the right dose for their conditions.

At ACS Laboratory, our comprehensive potency test which analyzes 11 cannabinoids is our most requested test. Clients who rely on precise potency testing range from cultivators who test before and after harvest, hemp processors who need accurate measures after extraction, and product formulators who need to test the raw extract they've sourced, as well as their final product (tinctures, salves and other CBD and THC infused products).

In this article:

  • Potency variation
  • Moisture content
  • Testing protocols
  • Plant variations
  • Strain variations
  • What you can do about it

Potency Variation

Today, the industry is evolving and responsible labs like ACS Laboratory are investing in state-of-the-art technology to ensure the most accurate results. States are also beginning to implement more stringent guidelines that require medical marijuana treatment centers to test with certified accredited labs.

However, a problem remains: Cannabis is still federally illegal, which means there’s no national industry standard or regulation. Many states have their own rules. Additionally, laboratories use different machinery and methods. Lack of standardization leaves room for error.

Along with testing method variations, cannabis itself is not a standard medicine. Cannabis is a plant, not a chemical, and therefore every batch, even within the same strain may vary in THC potency as well as other compounds including cannabinoids, terpenes, and flavonoids. Inevitably, some degree of deviation is normal and expected.

Moisture Content

Moisture content makes a difference when testing for potency in cannabis flower, because THC is measured as a percentage of the product’s total weight. So if the sample is dried out, it will weigh less than a sample with more moisture. Bot samples may contain the same amount of THC, but the test will indicate that the dry cannabis is more potent by percentage.

Ideally, all cannabis would be sold, processed and tested at the same moisture levels, but that’s not the case because there’s no industry standard. Certain medical marijuana companies dry the product out before sending it to the lab, and some labs remove all water from sample as part of their testing to achieve controlled results. Then before selling the product, companies may add water back to the samples to make the plant smoother, more flavorful, and pleasant to ingest.

This is a borderline manipulative practice, and inadvertently leads to mislabeling products.

Testing Protocols

Testing facilities utilize different protocols and equipment, which can skew THC potency results. Currently the two most common and accepted methods are Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC). GC is more cost effective and simpler, but generally less accurate due to the method of testing. GC uses a Flame Ionization Detector to heat the samples, which can cause the cannabinoids to degrade or change.

As a result GC tests must incorporate a second piece of equipment to properly identify the cannabinoids. This process, known as Derivatization, is subject to error and difficult to validate.

Unlike Gas Chromatography, HPLC can quickly identify and quantify cannabinoids without heating the sample by using an ultraviolet wavelength detector. HPLC is the Gold Standard of testing and is the method ACS Laboratory uses for all potency tests.

Plant Variations

Through no fault of growers, manufacturers, or retailers, potency results can vary based on which part of the plant is tested. For example, a supplier may send a sample from a particular plant’s flower that was exposed to sunlight and naturally contains a high percentage of cannabinoids. But if that same supplier had sent a bud from the under canopy instead, the results would be much different.

Under canopy buds are exposed to less light, which means they’ll inevitably contain less THC. Even when samples are carefully chopped up and homogenized, variations in potency tests are common--as shown in the Ring Test.

Strain Variations

Cannabis genes are the most important determinant of THC potency, but that doesn't mean plants of the same strain will contain the same exact amount of THC. In addition to genetics, the strain’s harvest time, growth methods, light levels, and curing process all play a role. If one batch is harvested too early, it will naturally contain less THC than the batch that matured for an additional 2-3 weeks. Harvest too late and THC can start to deteriorate.

Common mistakes like over- or under-watering, heat stress, and nutrient deficiencies can also play a role. In addition to growth method, light is a major factor that determines THC potency. That means the same strain grown outside vs. inside will also vary. Finally, curing is the normal process of delicately drying buds after harvest to enhance their look, effects, and taste. Flowers can be dried slowly over time, but if the process is rushed using heat or other means, cannabinoids and terpenes can be degraded.

What You Can Do About It

Without consistent testing or cultivation methods, the cannabis industry may have to deal with a level of uncertainty that affects everyone from growers to consumers for years to come. In the meantime, all industry participants can take steps to improve confidence in potency testing.

Growers can do their best to maintain consistent harvest conditions and ensure all samples sent for testing contain standard moisture and humidity levels. Processors in horizontal integration states can purchase products from trusted growers and have the product tested again to confirm the reported results.

Medical marijuana treatment centers, cannabis retailers, and consumers can do their part by working with reputable brands that show proof of potency testing from ISO/IEC 17025: 2017 accredited labs like ACS Laboratory. Not only does the team at ACS Laboratory adheres to regulatory standards, and use the most advanced technology, ACS also participates in the Emerald Test Program.

As members of the program, ACS Laboratory receives various samples with known THC levels. We test those samples, report the findings, and receive Emerald Badges of credibility for all accurate results.

The 2019 results recently came back, and the ACS Laboratory team was awarded more than any other lab in the eastern US. Among the 21 badges received, ACS Laboratory was recognized for potency testing in hemp bud, hemp oil, gummies, and solutions. We are proud of our position in the cannabis testing industry and will continue to innovate and exceed regulatory standards.

If you find yourself with questions about how you’re preparing samples for testing, when to test or if the results you’re getting seem a bit “off”, give us a call any time at (813) 634-4529 or contact us online.

The Cannabinoids Guide

This complete cannabinoid guide covers major and minor cannabinoids, how they work in the body, and highlights the top compounds brands and operators must test for today.
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The Cannabinoid Guide

The definitive resource on leading major and minor cannabinoids, how they work in the body, and what to test for.
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