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CBD and Bioavailability (absorption)

In our last blog post we covered dosage for a range of applications including oils, capsules and vapes. However as mentioned, metabolism and body fat % affect how CBD is absorbed and processed by the body. Meaning that even though a product has x concentration on the bottle, this isn’t necessarily the amount you will absorb.  

What is bioavailability?

This refers to how much, and at what rate, a substance is absorbed into the bloodstream. It’s important to understand this to determine how much you should take.

What is the bioavailability of CBD oil?

For you as an individual, this depends on how you take it, including inhaling, rubbing topically, and ingesting, as well as in what form its taken: isolate, distillate, full spectrum, along with other ingredients that it may be mixed with, your weight, and other medication that you may be on!

Intranasal / Inhalation

This is actually one of the most effective means of ensuring a high bioavailability. The intranasal bioavailability of CBD is around 40%, with some studies reporting it to be as high as 56%.

When inhaled such as through a pen, joint, bong or vaporiser, the contents can be absorbed into the lungs almost immediately, allowing it to enter the blood stream directly.

Sublingual (under the tongue)

The bioavailability of CBD when holding oil under the vascular mucosal area of the tongue, is around 16%, with some studies placing it as high as 35%.

While not as fast acting or strong as inhaling (around 20 minutes to take effect as opposed to 10), it can still be absorbed by the sublingual gland and enter into the blood stream.

The trick here is to make sure you don’t swallow too soon, and hold the drops for at least 60 seconds. Also be sure to place the drops under the tongue, not on top.


Popular because its easy, but not necessarily as effective, being the method with one of the lower bioavailabilities at around 10%, although some studies have found it to be as low as 6%.

This is because rather than having direct access to the bloodstream, it must pass through the digestive system first. This can take up to 2 hours for some people and a lot of the CBD is broken down in the liver and digestive tract. However when it does enter the blood stream, the effects may last for longer. 

This is applicable to edibles like baked goods, concentrates added to water, capsules and gummies. These are tasty and easy ways to consume CBD, so you will just need to bear in mind that the concentration needs to be higher to make up for the loss during metabolic breakdown. CBD also absorbs best when consumed with fats (best to keep them healthy fats such as MCT from coconut).  

Liposomal CBD (oral)

Cannabinoids are lipophilic, meaning they dissolve in fats not water. The problem is the human body is 60% water, hence CBD is not absorbed well orally. 

Scientists have therefore understood the importance of liposomes – a body of fat that surrounds or is attached to another molecule (a vitamin, pharmaceutical, or cannabinoid for example), allowing nutrients to be delivered more effectively.

This improves delivery but there are still other options that may offer better absorption.

Nano-emulsified CBD (oral)

Although CBD is hydrophobic, water-soluble CBD does exist. These particles don’t truly dissolve in water but can be made water-friendly, by reducing its size and increasing the surface area. Nano-emulsions are the most common for this purpose.

CBD as a nano-emulsion allows it to be absorbed at higher rates than other methods of delivery, the size therefore makes all the difference, with a 25 nanometer emulsion being absorbed more than 50%, whereas a 500-5000 nanometer (i.e. Liposomal) emulsion will have less than 20%. 

The downside to it being used up faster by the body is that the effects will not last as long, however you will use up less product possibly creating more value for money.


When applying CBD to the skin, it engages mainly with the Endocannabinoid receptors of the peripheral nervous system, so its best for more localised, targeted action e.g. dry skin or sore muscles.

The skin acts as a thick barrier layer, therefore in order for the contents to be absorbed, CBD should really be mixed with other components of the plant such as Terpenes, which its believed may help pull the molecules across, and application should be vigorous.

The bioavailability of topical CBD hasn’t yet been quantified, although it is expected to be at the lower end of the spectrum. Even so, multiple studies have still found purified CBD to be effective at providing local pain relief in some individuals. You can view an animation of how CBD interacts with the skin here


The average bioavailability of suppositories is around 13.5%, which is relatively high. This method allows CBD to enter the bloodstream via the vascular membranes in the anus and vagina.

If you prefer not to smoke and cannot take CBD orally, or desire localised action, then this is an excellent method of administration.  

As you can see, with such a huge range of options available, self-experimentation can often feel a little overwhelming. Nevertheless it is an important part of understanding how your body makes you uniquely you, whilst investigating the differences between the various modes of application and how they make you feel. 

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