Most budtenders will advise not buying cannabis based off the lab results because the numbers may not mean much, if anything.
The issue at hand is a lack of standardization across labs. One lab might test a sample one way, whereas a different lab will test it another way. The same sample of the same cannabis can get entirely different results, depending on the testing methods the lab uses.
One difference is what machine is used to test for THC. Some labs use gas chromatography (GC), while others use high pressure liquid chromatography (HPLC). Cannabis and extracts can be tested using either method. However, HPLC is often considered to be more accurate.
Testing methods are not the only cause for a variance in test results; another cause for variance is the moisture level of the sample being tested. In order for a lab to pass a sample of cannabis, the moisture level must be 15% or less. The issue here is that the same sample, when tested for THC with 15% moisture content, will test lower in THC than if it was tested at 5% moisture content.
There are other causes for inaccuracies and inflated results as well. One such cause could be that a grower only has to test one gram of cannabis per five pounds of flower. However, THC levels vary within a plant and from plant to plant.
It has been said that some growers may even be coating samples in kief or spraying them with a tincture high in THC in order to raise their test results, which is obviously fraudulent, but still persists.
This next problem is a little less straightforward: the labs themselves may be financially rewarded or penalized by the results they give. For instance, if one lab gives a result of 12% THC and a different lab gives the same sample a result of 25% THC, which lab is the grower going to choose?
What can be done about all of this? How do we get to a point where the lab results are accurate and can be trusted? The first change that must be made is to standardize all lab procedures. If two different labs test the same sample using the same testing equipment that has been calibrated in the same way, the results should be the same.
Next, test samples should have a smaller variance in moisture content. Also, the way the THC level is reported should not be an exact number. A range of THC can be reported instead of a supposedly exact number that is inaccurate for the lot as a whole. Instead of a package reading “THC: 23%,” it should read “contains THC,” “up to 23% THC,” or give a range such as, “contains 17–23% THC.”
Enforcing testing practices is also necessary. If testing procedure rules are not enforced, creating more rules does not matter. Creating punishments for fraudulent behavior and enforcing them is necessary. Removing the ability to retest a sample would also help, although this has already been done to some extent.
Until the testing system works, here is a little advice on how to buy cannabis: use the test results as one factor among many. Try different strains and find out what works for you. Inspect and smell the cannabis before purchasing. Most of all, build a relationship with a local budtender, as they are the ones who have the most access to the most varieties; they live and breathe cannabis. Find a good one and trust their judgment.