Refresh Checked Unchecked Menu Search Shopping bag Geolocation Person Facebook Instagram Twitter YouTube Info Icon CBC Icon CBC Shape CBD Icon CBD Shape CBG Icon CBG Shape THC Icon THC Shape THCV Icon THCV Shape Loading…
Advertise on Leafly

Cannabis Potency: How Does Lab Testing for THC and CBD Work?

August 18, 2017
Cannabis Potency: How Does Lab Testing for THC and CBD Work?(SEASTOCK/iStock)
Cannabis testing allows consumers to make informed purchasing decisions based on the strength and composition of cannabis products. Accurate testing is crucial for medical cannabis patients who need specific therapeutic effects. It’s also important for adult-use consumers because products vary widely in their potency, which will influence the experience.


Cannabis Testing: The Importance of Independent Third Party Analyses of Cannabis Products

There is a variety of cannabis testing methods used to evaluate safety, quality, and potency information to consumers. While the specific testing requirements vary by state, a few major testing procedures are common throughout the industry. Potency information in particular is a considerable drive for cannabis testing to provide information on THC and CBD levels in cannabis products.

Testing Cannabis Products for THC and CBD Levels

Cannabinoid potency data quantifies levels of plant cannabinoids present in cannabis products. Producers are required to obtain potency data for THC and CBD, the two most common cannabinoids. It’s important for consumers to know THC and CBD levels because these will have a strong influence on the effects of the product. For example, some medical patients may want a strain with a high CBD:THC ratio, while adult-use consumers may request the opposite.


A list of major cannabinoids in cannabis and their effects

Other compounds, such as minor cannabinoids and terpenes, can be tested for as well, although these measurements are typically not required by law. For this article, we’ll focus on potency testing for THC and CBD.

How Do Labs Measure THC and CBD Levels?

There is a variety of ways to measure THC and CBD concentrations. The most common technique is called High Performance Liquid Chromatography (HPLC). HPLC can separate and quantify a mixture of chemicals in liquid solution.

In HPLC, a sample is collected from cannabis flower mixed with a solvent such as ethanol. The solution is then pumped at high pressure through a tube. The tube contains a material that attracts some molecules in the sample based on their chemical properties. At the end of the column is a detector. Compounds that are attracted to the material inside the tube will travel slower and reach the detector later.


Leafly Investigation: Is Washington’s Top Cannabis Lab Inflating THC Numbers?

HPLC detectors typically measure UV light absorbance, which can be associated with specific molecules. When the molecules reach the detector, their relative abundance is measured. Because different cannabinoids, like THC and CBD, travel at different speeds through the column, they will be detected at different times, allowing for characterization of the sample.

General Overview of HPLC Process

Figure 1: General Overview of HPLC Process. The cannabis sample is injected into the system and the cannabinoids move through the column. Interactions between the cannabinoids and the column determine how fast each type of cannabinoid can travel through the tube. The detector quantifies the presence of each type of cannabinoid based on how long it takes to be detected. (Photo credit: Amy Phung/Leafly)

The THC and CBD values listed on the back of cannabis packaging come from these laboratory measurements. Since the values obtained in the laboratory are referred to directly by the consumer for product information, accurate potency testing is imperative.


How to Assess THC and CBD Levels in Cannabis Strains and Products

You can run your own DIY chromatography experiment at home using a strip of white construction paper, a black marker (you may need to find a specific type that will work well with this experiment), and a glass of water.

(Julia Sumpter/Leafly)

Use the black marker to draw a line across the strip, parallel to the paper’s edge. Sit the paper strip upright into the glass of water, making sure the marker line is just above the water.

DIY cannabis potency test (2 of 2)

(Julia Sumpter/Leafly)

Wait several minutes. The water will travel up the paper and separate the pigments in the marker.

DIY chromatography experiment results

(Julia Sumpter/Leafly)

Terpenes are more volatile than cannabinoids and require a different method of chromatography for detection. High volatility means that terpenes evaporate easily and are usually found in a gaseous state, whereas cannabinoids are stable in liquid solution. Due to the volatility of terpenes, a different lab technique is preferred.

Cannabis Testing Standardization

According to Confidence Analytics, a state-certified laboratory in Washington, “there are no strong regulations in place about how cannabis chemicals are measured. However, HPLC has emerged as the dominant technique for measuring cannabinoids.” In other industries, there are specific guidelines on testing methods and settings for laboratory equipment.

This lack of regulation can lead to discrepancies in potency data and inaccurate cannabinoid data. States are pushing to standardize cannabis testing and ensure that potency values are consistent across laboratories. In Washington state, a group of I-502 accredited laboratories are undergoing a “round robin,” measuring the potency of an unknown cannabis sample and comparing the results between laboratories. If proper testing practices are in place at each laboratory, reported potency data should be similar across the board.

(Note: Leafly is actively involved in the push to standardize cannabis testing as a member of The Cannabis Alliance, a group designed to promote transparency in the industry.)


How Strain Genetics Influence THC:CBD Ratios

A wide variety of testing should be completed to ensure the safety and quality of cannabis products. Distinct testing methods are used to collect data on terpenes, contamination, and residual solvent levels. Consistent and accurate testing is important for industry transparency and consumer safety.

Unfortunately, there has been controversy surrounding potency testing methods, with suspected inflation of THC concentration in some cases. Implementing standards for cannabis testing procedures has been challenging, as the requirements vary significantly from state-to-state. Consequently, the industry needs to push for a general, national standard for cannabis testing to ensure accurate potency reporting.


“High Performance Liquid Chromatography (HPLC).” HiQ, The Linde Group. [Website]
“Foreign Material & Microbial Bioburden Screening | Analytical 360.” Analytical 360 RSS. [Website]

Ashley Auerbach's Bio Image

Ashley Auerbach

Ashley is a Leafly intern researching medical cannabis. She is also a student at the University of Washington studying Molecular, Cellular, and Developmental Biology with a minor in Microbiology.

View Ashley Auerbach's articles

  • Is there a requirement for minimum sample weight?

    I heard 125g for flower to prevent “selection” of a primo bud that doesn’t represent the typical potency of the crop.

    • FLW

      I wonder, use 125g to get a good average over a few plants, but it takes only a small portion of the resulting liquid for the actual Chromatography test, and the scientists can use the rest of the remaining liquid at the end of the day for recreational use. I mean — the latest in-vogue nomenclature — “adult use.”

      • No, the entire sample must be used. The % of THC is always by weight. It’s an average from the whole sample. Again, to prevent sample bias.

        • Zachary Iszard

          Sampling is a principle problem with cannabis testing as it stands. In WA, the legal sample minimum is only 4 grams for a whole 2.27 kg lot, and growers prepare the samples meaning they can cherry-pick if they want.

          In all other agricultural analysis (and beyond), sampling representativeness is a HUGE concern, more than the variability within the lab. Very important point to bring up, thanks!

  • Nam Tuan Tang

    look very nice

  • Zachary Iszard

    Excellent article, great breakdown of how LC works! Spiffy diagram, too.

    I’m super excited to see more people getting interested in cannabinoid ratios, too! This is exactly the direction the data is pointing us — strain identity by chemical ratios, not only by name or by “sativa” or “indica” (meaningless terms for user experience).

    • FLW

      Although, the burning question is if there are significantly different user experiences for different varieties of Cannabis with the same CBD:THC ratio.

      • Herb

        Absolutely…and are there other factors that can mitigate the CBD and THC organically due to specific strain??? Also, I run every day. The endorphins are processed through the cannabinoid receptor system in the body. They feel different if I have smoked the night before. And even more important is that the endorphins do a splendid job of cleaning up any CBD/THC hangover. It’s hard to run some mornings. But it feels so much better a mile into it. Not to detract from your excellent point.

  • Frank Cassianna

    I feel more creases in my cranium, wonderful article, information one always wonders about, and have not the means to research… thank you.

  • Renay Watkins

    Not a fan of being st9ned or minted but i do need pain relif and sofar thc cbd and morphine are the only drugs i can use that dont get me stupidly high all though some thc in street weed is too hard so it meNs buying it changeing it tonedible or wrak vapeable and then experimenting i onow they make cbd isolate do they make thc isolate and if so could you mix the two to acheive the oerfect mix of low high and good health nobpain or big high and good health and nobpain

    • Michael Lioon

      Try TruGen3’s TruEase, no THc, but cbd and its in a small soft gel.

      • Ren Watkins

        Is it an american company or australian as the thc is for tje bone pain i just need less of it than normal cannabiss as atreet weed is too strong and finding actial cool strains unless youbgrow your ownbis impossible because of legalitys the health department nasically make chroinc pain syndrome paitents with fibromyalgia forced to do criminal activities or go onto methadone which is worse than morphine and oxys

        • Michael Lioon

          It is an American company. The CBD is what is responsible for helping with the inflammation and chronic pain, not the THc, so you don’t get any of the physiological side effects. Think of it as the same part in marijuana that helps your pain without the getting high part. Not sure if you have heard of the supplement company, Douglas Labs, or not, but they are the same people who started that company over 50 years ago so you know what you are getting is best in class.

          • Byrd Dawg

            And has many healing properties but what about the entourage effect, hearing lots on this over stictly cbd

  • The Global cannabis testing market has been valued at $809 million for the year 2016 and is estimated to generate a revenue of about $2112 million by the year 2025. At a CAGR of 11.4% in 2017-2025
    Read More:

  • minorgeek

    thanks for the DIY test description. but it must be missing parts. there’s nothing about using a sample of herb, in the water? or ethanol? or oil? and how does one interpret the results? if there’s an article on this, please let me know where. thanks!

    • AliceinWonderland

      I was also confused by the DIY test? Does anyone know what is missing in the instructions??? Also doesnt look like a black marker or white paper in the pics!????? TY

  • WellNowDear

    Most of the information I am seeing about CBD oil is not accurate. Impossible treat-all claims promising help with all sort of conditions is on just about every thread. Most of it is coming from dishonest or possibly deceived people pushing the hype. It has some very definite side-effect for “certain” people I have discovered after much searching. It is as if the consumer is somehow offensive if they even ask on many sites. I found many very hostile attitudes in some marketers when I questioned their unrealistic claims that CBD oil was some sort of “wonder drug”.

    All my questioning above followed on the heels of taking CBD oil exactly as indicated and experiencing some very negative side-effects of severe fatigue and severe re-flux followed by diarrhea. As days passed the symptoms became worse so I discontinued the use of it. I was fine again after several days with out the oil.

    The whole industry of CBD oil and the public as a whole are at risk due to the unscrupulous people who are not only making false claims but, are also pushing a product that may have higher levels of THC or CBD than is desired or even safe.

    I agree emphatically that third party testing is needed.