November 18, 2020

The Bioavailability of Cannabis Explained.

What you need to know.

‍Whether you consume cannabis for medical purposes or use vapes occasionally, it’s important to know about the bioavailability of cannabis. Understanding how it works with the various ways to consume cannabis can help you choose the delivery forms that are right for you.

What is bioavailability?

In order for a substance to work, it must first be absorbed by your body. Simply put, bioavailability is the amount of the substance that gets absorbed into your bloodstream and delivered to the targeted tissues and organs.1,2

One way to think of it is how much of the substance is available for your body to use.

Bioavailability is measured by the percentage that’s absorbed in the body compared to the product dose. For example, if 100 mg of a drug is taken orally and 70 mg of this drug is absorbed unchanged, the bioavailability is 0.7 or 70 percent.

In general, the higher the bioavailability, the lower quantity you need to experience the effects. For example, when more CBD is absorbed by your body, it causes a more potent effect.

Bioavailability varies from person to person

Many things can affect how well your body absorbs cannabis, including your age, general health, certain gastrointestinal disorders, and whether or not the product is taken with food.1

As well, the bioavailability of cannabis differs between the varying types of cannabinoids and the way they are delivered into the body. (e.g. whether you swallow or inhale it).

Ways to consume cannabis

There are three main methods of consuming cannabis: inhalation, sublingual and oral. Here’s an overview of each.

Bioavailability of dried cannabis

Effects are felt in 10 to 30 minutes

Effects can last up to 6 hours* 3

Because inhalation is the fastest method of delivery, many people prefer using cannabis this way. One study found that smoked THC had about 25-27 percent average bioavailability. 4 When smoking cannabis, effects are generally felt approximately 10 minutes after inhalation.3

With smoked cannabinoids however, much depends on the depth of inhalation, puff duration and breath-hold. Since the advantages of smoking cannabinoids are offset by the harmful effects of smoke, smoking is generally not recommended for medicinal purposes.

Bioavailability of vaping

Effects are felt in 10 to 30 minutes

Effects can last up to 6 hours* 3

Vaping, like smoking, utilizes the lungs to absorb cannabinoids. Since it’s generally considered to be safer than smoking, it’s being explored as an alternative to smoking. One study found that using a vaporizer was the best way to enhance the bioavailability of cannabis.5  Vaping devices come in all shapes and sizes. With the right vaporizer, bioavailability for both THC and CBD can be between 36%-61%.5

Bioavailability of capsules

Effects are felt in 30 min - 2 hours but 4 hours to feel the full effects

Effects can last 12 hours* 3

In contrast to inhalation, oral delivery systems have lower bioavailability. This is because the swallowed capsule needs to pass through the acidic environment of your stomach and then through the liver before it makes its way into your bloodstream. In some cases, the product may be transformed or metabolized by the liver before it reaches your bloodstream.1

One study showed that with orally administered prescription cannabinoid medicines such as synthetic THC, only 10 to 20% of the administered dose entered the bloodstream indicating extensive liver metabolism.4

Bioavailability of sublingual methods—oils and sprays

In this method which involves placing liquid drops under your tongue, the cannabinoids are absorbed directly through the mucus membranes of your mouth and nose, bypassing the liver and directly entering your bloodstream. Peak blood levels for this method, have been measured within about two hours, although there is wide variation between individuals between the time and onset to peak effects.

Bioavailability of topicals

These come in the form of lotions, ointments, bath salts and oils that are applied to the skin. Because cannabinoids are hydrophobic, meaning they repel water, penetration into the aqueous layer of the skin can be limited.  While not widely studied, some research shows that cannabinoid creams and balms applied to the joint have an onset of action in minutes, with effects lasting up to two hours. 6

Bioavailability of edibles

Effects are felt in 30 min - 2 hours but 4 hours to feel the full effects.

Effects can last 12 hours* 3

Edibles, which are foods infused with cannabis, encompass a wide range of products from baked goods (e.g., brownies, cookies), beverages (e.g., coffee, tea, juice and soda), candies (e.g., chocolate, hard and soft candies) just to name a few. As with the other oral forms, the bioavailability of edibles tend to be lower than inhaled forms and can be unreliable.4

In one study using an oral dose of 20 mg THC in a chocolate cookie, the bioavailability was shown to be only 4 to 12%.6  Another study, using chocolate cookies containing 40 mg of CBD found bioavailability was around 6%.4

Slow absorption can pose problems with edibles, especially for new users. Because they don’t work immediately, some people think they should take more to achieve the desired effect.  But ingesting more than the recommended dose within the correct time frame can result in unwanted side effects, such as panic and paranoia.4

Bottom line? Whether you prefer to consume cannabis through inhalation or edibles, always follow the dosage directions. If you’re a newcomer to cannabis, start low and go slow until you find the dose which may or may not work for you.


  1. Le J, Drug Bioavailability,
  3. Health Canada
  4. Cannabis (marihuana, marijuana) and the cannabinoids—information for health care professionals. Health Canada.
  5. Gieringer D, Cannabis Vaporizer Combines Efficient Delivery of THC with Effective Suppression of Pyrolytic Compunds. Journal of Cannabis Therapeutics. Aug 2003, 7-27.
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