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CBD Bioavailability: What Does it Mean Why is it so Important?

Updated: Mar 21, 2021

Not all CBD is the same. Discover the differences between CBD delivery forms and the pros and cons of each. Learn how to choose the best CBD form for you.

CBD offers great potential for health and healing. Its high safety profile and non-addictive nature make it an appealing alternative to many conventional drugs.

But, in order to be effective CBD has to reach your endocannabinoid system. This means it first needs to be absorbed into your bloodstream, a concept known as bioavailability.

Once there, it has to stay in circulation long enough to be delivered to the organs and tissues where it is needed.

So, how much of the CBD you take actually gets absorbed and used?

That depends on a process known as pharmacokinetics (how compounds are processed by the body).

In short, pharmacokinetics refers to the sum of your body’s mechanisms for absorption and elimination, the characteristics of CBD itself, and numerous external factors that can either help or hinder the way you assimilate and use CBD.

Additionally, the route of entry, or delivery method, has a lot to do with how much and how quickly CBD enters the bloodstream.

Bioavailability of CBD: Vaping vs Oral Consumption

In this article, we explore the various delivery methods for CBD, including oral, inhaled, mucosal, transdermal, and intravenous routes. We’ll discuss what the current science tells us about each method and their relative advantages and disadvantages in practical use.

We’ll also survey some of the important factors that affect CBD absorption and metabolism. And you’ll learn how you can best manage these factors so you can choose the ideal delivery form and dosage depending on what you’re looking to get out of the use of CBD.

This is a big topic, so let’s get straight into it.

Oral CBD: Capsules, Oils, and Edibles Oral CBD formulations, such as liquid drops, capsules, tinctures, foods, and beverages are among the most popular ways to consume CBD. But oral CBD has the lowest bioavailability of all delivery forms. On average, ingested CBD has a bioavailability of between 6-19%. One reason for this is that CBD is not readily absorbed when ingested and as a result, most of it is excreted without exerting any effects. This is due to the fact that CBD is fat-soluble (as opposed to water-soluble), which makes it a challenge for the body to absorb. Additionally, digestive acids and enzymes destroy a large percentage of CBD before it has a chance to be absorbed. And the small amount that gets through the intestinal wall is subject to being metabolized by the liver before it reaches the rest of the body. The half-life of oral CBD, i.e. the amount of time it takes for half of the CBD to leave the bloodstream, may be faster than other delivery methods. Half-lives from 10 to 17 hours have been reported for high dosages between 750 mg and 1500 mg. Peak levels of oral CBD tend to be lower than other delivery forms. In one experiment, cookies infused with 40 mg of CBD produced peak blood CBD levels between 1.5 and 3 hours after ingestion. However, the low absorption of oral CBD may be offset by certain advantages — such as a longer duration. A laboratory animal study found the average amount of time an orally consumed CBD molecule stays in the body, known as the “mean residence time”, was 4.2 hours. By contrast, the mean residence time for injected CBD, in the same study, was 3.3 hours. Oral CBD has also been found to lead to higher brain levels when compared to inhalation methods in animal studies.

Inhaled CBD: Vaping and Smoking Inhalation is an efficient way to consume CBD because it bypasses the digestive tract and liver allowing CBD to be readily absorbed through the thin membranes that line the air sacs of the lungs (alveoli) where it enters directly into the bloodstream. There are several ways to inhale CBD. 1. Smoking The most basic inhalation form is smoking. In this case the cigarette contains unprocessed CBD-rich hemp buds (as opposed to high-THC cannabis). Smoking has a bioavailability of 31% and a single CBD cigarette containing about 19 mg of CBD can produce peak blood levels within 3 minutes. The half-life of smoked CBD averages 31 hours. The downside to smoking is that it produces combustion by-products which can irritate and, in some instances damage the lungs. These include fluorene, pyrene, acrylonitrile, and acrylamide.

2. Vaping

A more elaborate and less irritating inhalation form similar to smoking is vaping — which is done with a vaporizer pen.

With this method, you draw liquid CBD oil held in a cartridge past a heating element that atomizes the CBD — producing a vapor that you inhale.

Vaping produces similar blood CBD concentrations and pharmacokinetics to smoking. There is some risk of lung irritation with vaping, though less than smoking.

3. Nebulizing

A nebulizer is a device that administers CBD in the form of a mist that is inhaled into the lungs. Nebulizers are generally used in hospitals to deliver medications to damaged or sensitive lungs.

Nebulizers produce peak blood levels in about 36 minutes.

Sublingual CBD: Drops & Sprays

This method takes advantage of the ability of CBD to be absorbed directly through the mucous membranes of the mouth and nose — bypassing the digestive process and going straight into the bloodstream.

1. Sublingual Drops

Peak blood levels for this method, which involves placing liquid drops of CBD under your tongue, have been measured within about 2 hours [5].

A simple way to improve absorption of sublingual CBD is to hold the drops under your tongue for 20-30 seconds before swallowing. Doing allows more time for your mucous membranes to absorb the CBD before it enters the digestive tract.

2. Oral Spray