Understanding the Bioavailability of Medical Cannabis

The bioavailability of cannabinoids is affected by a number of factors, including the method through which cannabis is taken.

There are a number of ways to take medical cannabis these days, so how do you know which products will work best for you? There are plenty of factors to take into account, including safety of the method, the product’s flavor, the ingredients used in its creation, and even a product’s potency or overall strength.

There is one point, though, that many people don’t consider when choosing their prefered medical cannabis product – bioavailability.

Affecting the levels at which cannabinoids are absorbed and used by the body, understanding bioavailability can help you get the most value out of your medical cannabis products, saving you money and increasing the effectiveness of your medical cannabis.

What is Bioavailability?

Cannabis is present in a number of products that are consumed using a variety of methods of administration. These different products, including pure hemp oils, tinctures and liquids, CBD capsules, chewing gum, vaporizers, and topical salves, offer different routes of administration for the main active ingredient – CBD.

The route of administration is defined as “the path by which a substance is taken into the body: for example, sublingually, orally, inhaled, or topically on the skin.”

The route of administration of any compound is extremely important since it can determine how the body takes in, distributes, and eliminates the supplement, and this is true of CBD as well. The route of administration can consequently affect how effective a CBD supplement will be.

The absorption of a supplement is its transfer from the site of administration to the bloodstream. The medical term for this absorption is called the bioavailability, defined as “the degree and rate at which a substance (such as a drug) is absorbed into a living system or is made available at the site of physiological activity.”

A substance delivered intravenously is assumed to have 100% bioavailability, and other routes of administration are compared to the intravenous route as a ratio for the percentage bioavailability. It is accepted that CBD and THC have related bioavailabilities.


The most common route of administration of medicinal cannabis products is via the oral route. This is the easiest way in which consumers can have the product, particularly because cannabinoids can be incorporated into many food products or can be ingested easily via capsules. Participants of one study consumed chocolate cookies to get a serving of 40 mg of CBD and the bioavailability was reported to be 6% (compared to intravenous administration).

First pass metabolism is the main reason for the low oral bioavailability of CBD. First pass metabolism is caused by the actions of enzymes of the digestive system before CBD reaches the circulatory system. CBD is acted on by enzymes in the liver called CYP450 mixed function oxidases to yield more than 100 different metabolites. Many of these metabolites cannot be used by the body and are soon excreted from the body.

There are a number of ways that oral bioavailability can be enhanced. Once such way is by taking CBD with medium and long-chain triglycerides (fatty acids). A recent study suggested that co-administration of CBD with these fatty acids can bypass some first pass metabolism. RSHO™ liquids and tinctures are formulated using pure hemp oil and medium-chain triglyceride (MCT) oil for just this reason, giving the CBD in these products the correct fatty acids necessary for higher bioavailability.


The sublingual route of administration holds the cannabis product, whether it is a tincture or lozenge, under the tongue, allowing the cannabinoids to be absorbed through the mouth.

A study performed with rabbits compared the bioavailability of oral and sublingual CBD solutions. The results of this study showed that the CBD delivered sublingually showed significantly higher bioavailability than the CBD delivered orally. On average, sublingual absorption has a bioavailability of between 15-25%.

The sublingual route of administration also bypasses first-pass metabolism, as the high abundance of capillaries below the tongue allow CBD to quickly enter the bloodstream through this route.


Often attributed more to recreational cannabis use than therapeutic, this route of administration does have benefits in terms of attaining a higher bioavailability than when cannabis is taken orally. Therefore, users feel the psychoactive effects of THC faster when inhaled as compared to taking it orally. One study estimated bioavailability of THC after inhalation was 18%. When cannabis is vaporized instead of combusted, bioavailability jumped to 40% in one study.

The high bioavailability seen with this route of administration is due to the fact that the lungs have high permeability, a large absorptive surface area, and a good blood supply for cannabinoids to enter circulation, bypassing first pass metabolism from the digestive system.


Cannabinoids can also be applied topically to the skin. This set of products, referred to as CBD topicals, include cannabinoid-infused lotions, balms, salves, and even bath and beauty products.

Topicals are non-psychoactive, so they are often popular among patients who want the therapeutic effects of cannabis but not the “high”. This non-psychoactivity is because the cannabinoids in these topicals bind to CB2 receptors near the skin, activating the endocannabinoid system, and are never absorbed into the bloodstream. Because human skin has a low absorption rate for these cannabinoids, coverage and concentration need to be large enough to overcome this barrier. This is why most cannabis topicals suggest applying “liberally” to the affected location.

However, CBN and CBD are more permeable to the skin than THC and are more likely to stimulate the CB2 cannabinoid receptors, making them the popular choice for the manufacture of cannabis topicals.

The medical literature that has been published indicates that, because cannabis infused salves and balms are non-psychoactive and affect only the region to which they are applied, they are the most effective application of cannabinoids for localized relief from pain, tension, muscle ache, and inflammation.

What Affects CBD Absorption

Although many studies mention average bioavailability ratios, actual numbers may vary from product to product, method to method, and user to user. Much of the research surrounding cannabinoids in part examines their bioavailability and ways that it can be increased.

It has largely been accepted that having healthy levels of saturated fats in your system gives cannabinoids higher bioavailability. Healthy foods high in the necessary fats include all dairy foods with 2% or more fat, eggs, non-factory farmed beef, lamb, pork, and chicken, fish, shellfish, cocoa butter, palm oil, coconut oil, and more.

Dialing in Your Perfect Serving

The bioavailability of cannabinoids is still something researchers are still working to fully understand, and different studies sometimes produce different percentages of bioavailability.

Therefore, finding an administration method and desired milligram number for medical cannabis can be difficult, relying strongly on personal choice. Rather than choosing based on bioavailability, select the method with which you feel most comfortable.

It is suggested that new users start out lower than their intended serving size and work their way up slowly over time. While a small serving is often as low as 10-15 mg of CBD, it is not unheard of to take a serving as high as several hundred milligrams.

Learn more about medical cannabis, including ways to take cannabis products, on our homepage by scrolling down to our medical marijuana overview or visit our news feed to read about developments in the cannabis industry.