How to Test THC Potency at Home

Most weed smokers use their senses to determine how potent their flower is. If they only get a mild buzz, the bud isn’t very strong. If they get blasted out of their mind, it’s incredibly potent. That’s the only test they really need.

Those who have the freedom to buy pot at dispensaries have numbers they can associate with their experience. Products sold at licensed dispensaries will have potency labels based on independent lab analysis, spelling out the product’s THC and CBD content.

So why would anyone want or need to test marijuana potency at home? For that matter, are there reliable and relatively inexpensive ways to do it?

Let’s answer both of those questions.

Why Test Marijuana Potency?

There are four groups of people who might want to test marijuana potency on their own.

• The most obvious home testers would be budding home growers (sorry about the pun), who’d understandably want to gauge how successful their growth has been. Those growing weed to sell would naturally want to test its potency as well.
• The second group is people buying from a dealer who they don’t know or trust. Testing the potency of their purchase would give them an idea of the dealer’s honesty and reliability.
• Potency tests can be particularly important to medical marijuana patients who aren’t buying from a dispensary because they’re more concerned with exact dosages than with getting high.
• Home bakers might also want to test THC content, since getting the potency of edibles right is an art rather than a science.

There’s one group we haven’t mentioned yet: everyone else.

Why would you want to test weed you’ve bought from a licensed dispensary or a dealer you trust? The answer comes from a study done at Johns Hopkins University.

They bought edibles in three different states and compared their actual THC content with the amount listed on the products’ labels. The results were shocking.

60% of the edibles had less THC than promised, and a few had virtually no THC content at all. On the flip side, 23% had more THC than promised — and a few had as much as 50% more THC than they were supposed to.

Experts say the differences are understandable because testing edibles is an extremely difficult process. Even so, the Johns Hopkins results show that there’s an obvious problem.

Medical patients might not be getting enough THC to treat their issues, or they might suffer unwanted side effects from a dose that’s way too high. Ordinary users could simply wind up with an unexpected and potentially unpleasant experience.

So it makes sense to test marijuana potency on your own. There are three ways to do it.

1. Pay for Lab Testing

This is the most expensive approach, and it’s probably not a reasonable option for ordinary weed consumers. However, you can have a laboratory test your cannabis even if you’re not a dispensary or large-scale producer.

Two types of labs will measure the cannabinoid content of your sample.

ISO Labs

ISO-certified labs are the ones that conduct full-scale testing of the marijuana you purchase at dispensaries. (ISO is a body that certifies the standards of third-party organizations.)

These labs typically provide complete packages that measure THC, CBD, and other cannabinoid levels, and search for chemical and microbial contaminants. Those tests don’t come cheap. You’ll usually pay at least $100 per sample, and the turnaround time can be weeks.

One other problem: there aren’t a lot of labs that can perform these detailed tests, so there may not be one in your state — and you probably don’t want to start shipping weed samples through the mail.

Local Testing Centers

The growing number of home growers has led to an innovative approach to testing in some cities and states.

Some dispensaries and cannabis companies have set up smaller, non-ISO testing centers to service independent growers and customers. These centers can be found in states as varied as California and Vermont; you might pay $40 or $50 to find out how much THC and CBD are in your sample.

2. Smart Phone Analyzers

Another very expensive way to test marijuana potency at home is to purchase a piece of test equipment that connects to your phone.

Companies like MyDx and Purple Scientific sell these sensors, and they’re quite simple to use. You just place a weed sample into a smart device that connects to an Android or iPhone via Bluetooth; it quickly measures cannabinoid and terpene content and displays the results on your phone.

If you have a lot of strains to test, this approach may be cheaper than submitting a number of samples to a lab. But the initial price isn’t for the faint-hearted; these weed analyzers can run you between $1,000 and $1,500.

3. Home Test Kits

The chemistry set you may have owned as a kid was good practice for testing your marijuana’s potency at home because you use most cannabis test kits virtually the same way.

A tiny amount of weed (less than ¼ gram) goes into a sealed test tube, you add a small amount of the supplied testing fluid and shake vigorously, and then let the vial sit for ten minutes or so. (Some kits have you use slides instead of vials.)

The solution will change color, and you compare it with the included color chart. It will tell you approximately how much THC is in your sample.

“Approximately” is the keyword. These home kits aren’t able to measure exact amounts of THC; they usually give you a range of values. For example, your weed might contain 1%-5% THC, 10%-15% THC, or more than 20% THC. Is that enough information for your purposes? Only you can answer that question.

These “bare bones” kits generally contain enough equipment for 5-20 samples and cost about $5 per sample. Some also measure CBD content. CB Scientific and Cannalytics Supply are two brands to look for.

How To Test Marijuana Potency at Home: FAQ

Q: Are at-home potency tests really accurate, at least within their limitations?
A: That’s an interesting question. Obviously, a test that tells you a sample has 10%-15% THC content isn’t really “accurate,” but there’s a bigger issue that impacts ISO lab testing as well. You probably know that flower doesn’t contain much THC until it’s burned, vaped, or decarbed; it contains the precursor cannabinoid THCA instead. So the reported amount of THC in weed is only an approximation based on how much THCA is in the sample. The “real” amount of THC that will be in the weed when it’s smoked or decarbed depends on the level of heat it’s exposed to. Labs are pretty good at coming close, but no potency test can be exact.

Q: Is there any way to measure the potency of THC once it’s been burned or decarbed?
A: Not really. The closest you can come is to smoke the weed and immediately have a blood sample taken to be sent to a lab. That’s not only an inconvenient option, but it’s expensive — and it will still only be an approximation.

Reference

• Vandrey, R., Raber, J. C., Raber, M. E., Douglass, B., Miller, C., & Bonn-Miller, M. O. (2015). Cannabinoid dose and label accuracy in edible medical cannabis products. Jama, 313(24), 2491-2493 [1].