As anyone with even rudimentary experience using cannabis can tell you, potency can vary. A lot. Sometimes that can be half the fun—learning just what effects a new strain will have and how strongly you’ll experience them.

But if you’re a medical marijuana patient, cannabinoid potency can be a very important factor in your therapy. Cannabis from a MMJ dispensary, if you have access to one, will often be laboratory tested. The results from these analyses can help guide a patient in selecting a strain with the right cannabinoid potency and ratio to give the desired effect.

If you’re growing your own herb, or getting it from a source that hasn’t tested it, there are options available for you to determine its potency. If you live in a state that has legal weed, there may be a commercial lab near you that performs potency, contamination and other tests on samples you provide to them. But lab tests can be costly, running about $40 or more for each potency analysis.

Options to do your own potency testing are available online, but do they work?

That’s what I wanted to find out, so with the help of San Diego cannabis testing facility PharmLabs, I put the tests to the test.

After reaching out to the manufacturers of several testing options, three agreed to provide their product and participate in my admittedly unscientific experiment. I’d like to thank these companies and PharmLabs for their invaluable assistance with this project.

To run my experiment, I performed the different tests as directed. I used samples of cannabis flower from batches tested for potency by PharmLabs with their gas chromatograph lab equipment.

My goal was to compare the results I obtained from the home testing options for THC and CBD potency, with the lab results provided by PharmLabs, to see if they were consistent. All the manufacturers suggest running multiple tests on several samples from a batch and determining averages for the most precise results.

The first products I tried were Test 4 Detection Kits by CB Scientific. I tried individual tests for THC or CBD, there is a combination test available as well. These are very simple kits that only require a small pinch of herb, added to a container with a test fluid. After a good shake and a few minutes wait, the color of the sample is compared to the included reference chart. A color match determines a range of potency, rather than a precise number.

All the results I received from the CB Scientific products were consistent with the PharmLabs results. The potency ranges on the reference card top out at 20 percent THC and only 2.5 percent CBD, so if your sample is stronger, you won’t know by how much. But if you just want a good idea of the potency of the sample you’re working with, the ease of use makes the CB Scientific products a great option. They are priced at $30 for three tests.

If you are looking for results with greater precision, or an even lower cost per test, the other products I tried may better fit your needs.

Photo by A.J. Herrington

Photo by A.J. Herrington

These two kits use a process called thin layer chromatography (TLC). The products I tried were Cannalyse 20/25 THC Test Kit by Cannalytics and the CTK Test Kit #1 from TLC Lab Supply. Although a more involved and technical process, more precise results can be obtained with the thin layer chromatography options. Although I was only looking at THC and CBD, about a half-dozen different cannabinoids will render on the plate.

To perform these tests, a 0.1 g sample of flower is mixed with a test fluid. Very small samples of the mixture are precisely measured and applied with a pipette or capillary tube to a specially coated glass plate. The plate is then placed in a jar, standing in additional test fluid. The fluid then wicks up the plate, carrying the cannabinoids with it. The individual properties of the cannabinoids cause them to be left in line, in a particular color and specific order, up the plate. Once the plate is dry, it is sprayed with a dye to reveal the colored spots. The size of the spots is compared to a template, which determines potency results in increments of one percentage point.

You might feel like you’re on CSI with this process, and as Roger Green from TLC Lab Supply noted, there is a definite “learning curve” that goes with performing thin layer chromatography. In fact, his company offers classes in three states to learn the procedure from a qualified professional.

Many variables, such as dryness of the sample and precise measurements, must be accounted for. After a few attempts with inconsistent results, I was able to perform tests with both kits that matched, within one percentage point, the numbers obtained by PharmLabs.

Photo by A.J. Herrington

Photo by A.J. Herrington

The TLC Lab Supply CTK Test Kit #1 is available for $160 and will test up to 25 samples. The Cannalyse 20/25 will also test up to 25 samples and costs about $150.

I only tested flower for my experiment, but all the products I tried can also be used for concentrates. The TLC options are appropriate for edibles, as well. CB Scientific offers a separate test for edibles at $40 for three tests.

After running the tests and comparing the experiments, I concluded that, with a little practice, home testing for cannabinoids can be done with a fair degree of accuracy.

However, potency testing is only one service offered by professional laboratories. Contamination from pesticides, molds, bacteria and other foreign substances can be a serious concern. Patients with sensitivities or compromised immune systems might consider insisting on products that have passed contaminant tests as well.

But if all you’re looking for is data on potency to fine tune your garden or titrate your dose, home testing can be a viable and economical option.

RELATED: Take A Peek Inside This San Diego Marijuana Lab
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