As approval of medical marijuana spreads state by state, labeling problems have led to errors


Today, 33 states plus the District of Columbia (Washington, DC) have legalized medical marijuana (and 11 states plus DC have legalized recreational use of marijuana). Medical marijuana is different than the street product. With medical marijuana, growers must confirm the products’ contents, so this information can be passed on to dispensaries and patients. However, each state has its own regulations for medical marijuana. This has resulted in a wide variety of medical marijuana products and safety concerns, particularly with the labeling of these products.


Active Ingredients of Medical Marijuana

The scientific name for medical marijuana is Cannabis sativa. Much like the different varieties and tastes of apples, medical marijuana comes in many different strains that produce hundreds of chemicals called cannabinoids. These cannabinoids are produced in side mmvarying amounts based in part on the growing conditions.

The two most notable cannabinoids in medical marijuana are tetrahydrocannabinol (THC) and cannabidiol (CBD). THC affects the mind, behavior, and coordination, causing symptoms similar to intoxication such as euphoria (happiness), relaxation, pain relief, and memory impairment. The intensity of these effects tends to be dose-related, so taking too much medical marijuana with high levels of THC may make people feel anxious and uncomfortable. Even when taken in small doses, symptoms similar to intoxication might cause light-headedness, increasing the risk of falls. THC has been linked to marijuana addiction (cannabis use disorder).

CBD does not produce euphoria. Initial studies suggest it may help reduce inflammation, pain, nausea and vomiting, anxiety, and seizures from epilepsy. Unfortunately, when some people cannot immediately feel the effects of CBD, they may take higher doses than they should. Common side effects include headache, diarrhea, restlessness, and sleepiness. CBD has not been linked to marijuana addiction. 

Dosage Forms

Medical marijuana comes in various forms so it can be taken different ways. While each state may approve different forms of medical marijuana, the most common are:

• Liquids and capsules taken by mouth
• Vaporized products that are inhaled
• Sublingual drops that are placed under the tongue (often called tinctures)
• Creams and ointments that are applied to the skin
• Edibles (which are highly discouraged for patients with children in the home)

Confusing Labeling 

The amounts of THC and CBD in medical marijuana products must be listed on the label. While the total cannabinoid content must also be included on the label, only the individual quantities of THC and CBD are required. The amounts of THC and CBD are important to know to manage each patient’s symptoms. However, the way these are listed on labels is confusing and can lead to errors. Here are just a few examples of how poorly labeled medical marijuana products can lead to errors.mm1

Inconsistent labeling. The amount of THC and CBD in medical marijuana products can be listed as either a ratio or a percent. A ratio shows how much of each major cannabinoid is contained in the product in relation to the other. So, a 5:1 THC to CBD ratio means that there is 5 times more THC than CBD in the product. A percent may show the strength of the THC and CBD contained in the product. But neither the ratio nor the percent simply tell you how many mg of THC and CBD are in each “dose.” Worse, there is no requirement to consistently use a percent or ratio on medical marijuana labels (Figure 1). So, even if you learn how to decipher a ratio, for example, your next purchase may list the percent of THC and CBD in the product. This has led to confusion regarding how much to take for each dose.


Variable order of ratios. If the THC and CBD amounts are listed on the label as a ratio, which cannabidiol gets listed first can vary. So the label may list the ratio as CBD:THC or THC:CBD. No federal regulations exist about which to list first, and most state regulations are silent on this issue. The order of THC and CBD in the ratio may differ even between products from the same grower, causing confusion when determining which product to use.

No volume with percent. In place of (or in addition to) ratios, some labels list a percent. This makes it hard to know the amount of THC and CBD in the product. For example, would you be able to easily figure out the amount of THC and CBD in 1 mL of a 0.037% medical marijuana product? It is vital to know the actual mg amount of THC and CBD in each dose. This is especially important for THC, which is most likely to cause both the desirable and undesirable effects. Even when the mg amount of THC and CBD is listed on the label of a liquid medical marijuana product, too often the volume is not included. This makes it hard to figure out how much to take for each dose. For example, would you know how much to take if the container simply listed 330 mg on the label instead of 330 mg per 5 mL? The Sidebar (on right ) describes an example of how difficult it is to determine how much THC and CBD are in each dose.

Look-alike containers and labels. Look-alike containers and labels have also led to confusion between products containing different ratios of THC and CBD. This is a big problem with products from the same grower because they are often packaged in similar looking containers (Figure 2).

Unlabeled bottles and cartridges. For some liquid products and almost all vapor cartridges, only the outer box is labeled. The bottle or cartridge itself is not labeled at all (Figure 3). If the box is discarded or lost, the unlabeled product may be confused with something else.

Missing information. The labels on some medical marijuana products may fail to list important ingredients. Or, the labels may fail to include important information that is needed to properly use the product. For example, the labels on some patches do not note the dose provided by the patch or how long the effects last (duration).  mm3

Inaccurate labeling. The only medical marijuana product approved by the US Food and Drug Administration (FDA) is prescription Epidolex (cannabidiol), which is used to treat seizures. In addition, FDA has approved a synthetic THC product, dronabinol, used to treat nausea and vomiting caused by cancer medicines and loss of appetite in people with human immunodeficiency virus infection (HIV). However, all other forms of medical marijuana are not approved by FDA. Therapy is considered investigational and safety is not fully understood. CBD-only products that are routinely sold on the internet and in stores also have not been evaluated by FDA for potency, purity, or safety. However, there are many reports of CBD-only products containing either no detectable CBD, or significantly more CBD than is on the label. Furthermore, studies have found that approximately 1 in 5 CBD-only products contains detectable amounts of THC.1,2 This means patients may unknowingly become impaired as well as test positive on urine drug screen tests for THC.

Here’s what you can do: National labeling standards are clearly needed for medical marijuana products to accurately list the THC and CBD contents and concentrations. However, until then, patients need to know how to interpret the label information.

First, the healthcare provider who recommended medical marijuana for you should ideally have also recommended the right dose and frequency of use that would be best for you. But most physicians have very little knowledge about medical marijuana. So, it is best to go to a physician- or pharmacist-run medical marijuana clinic or dispensary to obtain your medical marijuana. That way, a medical professional who specializes in medical marijuana can help you choose the right product and interpret the label information to ensure you get the right dose. Otherwise, you may be overwhelmed by the choices available and get confused by the label information. Ask for a demonstration of how to measure each dose of the product you select. Repeat the directions back to the medical professional to confirm you understand. You should also ask for written instructions so you don’t have to remember how to take each dose. You can also verify the amounts of THC and CBD in your product using the dispensary online menu to be sure it contains the amounts you need.

If you already have a container of medical marijuana and are uncertain how to read the label, take the container to a medical marijuana dispensary and ask questions. Remember, salespeople (wellness associates) at a dispensary are doing the best they can, but their level of training may not be at the same level as a medical professional with specialized knowledge of medical marijuana.

If the actual bottle or cartridge is unlabeled, keep it in the labeled carton so it can always be identified. Some growers include a sticker you can place on the bottle or cartridge.

Finally, when using medical marijuana products, consider keeping a journal to write down how you are responding to each product and the timing of doses. This information can be useful to adjust your instructions if needed. Also, be sure to try only one new product at a time to make sure you can tolerate it and that it is working.

ISMP thanks Christine Roussel, PharmD, BCOP, Director of Pharmacy at Doylestown Hospital in PA, for providing information for this article.


1. Bonn-Miller MO, Loflin MJE, Thomas BF, Marcu JP, Hyke T, Vandrey R. Labeling accuracy of cannabidiol extracts sold online. JAMA. 2017;318(17):1708-9.
2. US Food and Drug Administration (FDA). Warning letters and test results for cannabidiol-related products. April 2, 2019.

Created on January 3, 2020

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