What is CBD absorption?

Before compounds like nutrients, medicines, or other drugs can induce an effect, they need to enter our body and travel to the site of action. The process of the medication entering the body is known as absorption, and it describes the rate and extent to which a compound, such as cannabidiol (CBD), enters the bloodstream. There are several ways or routes for CBD to be absorbed. These routes are called administration methods, and each one has its benefits and flaws.

Common administration methods

The most straightforward route of getting compounds into the bloodstream is intravenously, via direct injection into the vein, which is invasive and generally considered to be unpleasant. For CBD, other routes are more common, including administration via the mouth (oral), via the mouth mucosa (on the inner side of the cheek, called buccal, or under the tongue, called sublingual), through the skin (transdermal), and through inhalation via the lungs (intrapulmonary), such as with smoking or vaporizing. It is also relevant to understand bioavailability, i.e. how much of a compound eventually gets absorbed into the bloodstream, which we will discuss below. The amount of a compound that is absorbed will determine the preferred method of administration and the optimal dose of CBD in order to reach the desired effect. (Huang et al., 2008) In general, the faster the absorption takes place, the faster the effects will be noticeable. At the same time, when the absorption stops, the effect will usually be over relatively quickly.

Comparing CBD administration methods

Of the common CBD administration methods, inhalation results in the fastest absorption, and consequently, effects happen faster. Inhaled CBD is transported to the blood vessels in the lung tissue and is detectable in blood within five minutes. (Ohlsson et al., 1986)

Taking CBD oil sublingually, buccally, or orally, results in a slower absorption whereby the effects can take hours to happen. (Mechoulam et al., 2002; Russo, 2008; Stott et al., 2013) Once CBD is detected in the blood, it can be measured for a much longer duration than after inhalation if you compare results from studies with only inhalation or only sublingual/oral administration. Studies comparing inhalation vs. sublingual/oral administration directly are, however, lacking. (Millar et al., 2018) Food intake can change the absorption of oral or sublingual CBD compared to no food intake and increase its peak concentration. (Stott et al., 2013) This means that CBD effects could change as well after food intake.

A topical (or local) CBD application differs from other administration methods mentioned, as CBD will not penetrate the skin and enter the central bloodstream. Animal studies have shown that topical applications can relieve local pain, although the exact mechanism of action is still unclear. (Hammell et al., 2016)

Factors influencing CBD absorption

The absorption of CBD depends on many factors, such as the compound composition that includes absorption enhancers like oil solutions, mode of administration, dose, simultaneous use with food or other compounds, and individual physiological characteristics. (Huestis et al., 2007) All these factors can influence how much CBD is absorbed (bioavailability), how quickly absorption happens, the duration of the period of absorption, how high the maximum CBD peak will be, etc. A full appreciation of these factors will result in the safest method and most optimal effect when considering CBD. One of the most important factors, bioavailability, will be explained in the following section.

Bioavailability

Which product gives stronger effects inside the body: 100mg of sublingual cannabidiol (CBD) drops, or 500mg of CBD in a skin cream?

A lower dose does not always mean that an effect is weaker. Although many aspects determine the answer to questions like the one above, one of the most important factors is bioavailability. Bioavailability refers to the exposure of the compound to the body. In other words, how much of what you ingest will eventually be distributed throughout your body to the tissues where the compound is needed? If you swallow CBD oil, it does not necessarily mean that it is actually in your body. To give an unusual example: before swallowing cocaine, illicit drug smugglers first encapsulate it to make sure that the cocaine is not absorbed by their body. This way, the capsules leave the body unchanged and without ever being absorbed or exposed to the body’s interior (the bloodstream and tissues), as the gastrointestinal tract from mouth to anus is a hollow pipe. The smuggler example is the opposite of what you want to happen with nutrients, supplements, and medicines; the more you can absorb, the less you will need to take. Perhaps some exceptions are ice cream and chips, but apart from your favorite snacks, you generally try to minimize the dose needed.

Back to the topic: Bioavailability is the amount of substance that reaches the bloodstream and represents a portion of the compound that ultimately enters the blood. It is a percentage of the total dose administered. The higher the bioavailability percentage, the higher the amount of a compound that enters the bloodstream.

Different CBD administration methods and bioavailability

Bioavailability of 100% is achieved only when a compound is administered intravenously (directly injected into the bloodstream). Different routes of administration will lead to a different bioavailability. This can significantly vary per product due to factors like absorption enhancers, but in general, this is the rule:

Vaporized products and smoked products have a higher bioavailability than oral and sublingual products, which have a higher bioavailability than transdermal products. These bioavailability comparisons have also generally found to be true for CBD, with an oral bioavailability between 6-20%. (Huestis, 2007; Millar et al., 2018; Ohlsson et al., 1986) Topical products have no exposure in the central blood circulation but act topically (locally).

Ingesting oral or sublingual CBD products after a (high-fat) meal can result in a five-fold higher bioavailability than when taking them on an empty stomach, but due to high variability of this finding, the effect can be different from person to person. (Stott et al., 2013)

To answer the question from the beginning of this section: ”Which product gives stronger effects inside the body: 100mg of sublingual CBD drops, or 500mg of CBD in a skin cream?” The answer is: 100mg of sublingual CBD drops, and possibly even more so after ice cream and chips.

Highlights

• Absorption is measured by the amount of a compound that gets into the central bloodstream.
• Different administration methods will result in different absorption speed, duration, and total compound exposure.
• CBD is absorbed fast when inhaled but after sublingual, buccal, or oral administration, it generally stays in the blood longer.
• Bioavailability is the portion of the compound that ultimately reaches the blood, expressed as a percentage.
• High-fat foods can increase oral and sublingual CBD exposure.