CBD bioavailability

By Dr. Barry Morrison

Whether you’re new to CBD, or an experienced user, we all have the same concern… “How do I get the most effect out of my CBD?”  The key to this is CBD bioavailability. If you are wondering what this is, then you are going to want to pay attention!

It’s critical to understand bioavailability and how it differs depending on your CBD delivery method. This will differ when comparing CBD that is water soluble vs. a typical CBD that is a fat-soluble oil. Here we will be focusing on the fat-soluble CBD oil.

What is the Bioavailability of Your CBD?

As you may be aware, CBD comes in many various forms. This may include oral, sublingual, vaping, intranasal, transdermal, suppositories and topical lotions. Each typically comes in multiple concentrations of CBD. If you’ve never used CBD or are fairly new to the industry, all these different options can be rather confusing.

You may want to try CBD, but which method should you use and how much CBD should you take? These are crucial questions that can all be addressed by understanding what bioavailability means.


Bioavailability Defined

In short, bioavailability is the degree and rate at which a substance is absorbed into the bloodstream and available for use by the body.

Bioavailability determines how much of what you took is actually present to provide a specific level of effect. Typically a medication ordered by your doctor already includes the degree of bioavailability when determining the standard dosage.

Therefore, the bioavailability of CBD varies based on the delivery method and concentration of CBD in the product in question. So, what is the best way to take CBD?

The Best Way to Take CBD?

Now, if your desire is the greatest bioavailability from your CBD, the most direct route would be intravenous (IV) administration. This means injecting directly into the bloodstream through the veins. The IV method delivers 100% of CBD into the body, however it’s probably not the most convenient or appealing option.

As for most of us sticking ourselves with a needle isn’t the most desirable way of administering our CBD. Let’s talk about some of the other methods of using CBD, and how each affects CBD’s bioavailability.

Oral CBD

Immediately swallowing CBD is slower to act resulting in a lot less entering the bloodstream. However, it does have a longer lasting effect on the body.

It was reported in a study that stated that approximately 6% of the CBD that is swallowed is actually absorbed and used by the body. This includes a tincture, if it’s swallowed right away, a capsule or edible. Each of these methods enter the stomach which breaks down a portion of its contents.


Gastrointestinal Absorption

In the gastrointestinal (GI) system a reduction of its absorption takes place. The GI process exerts its action of gastric enzymes on the CBD prior to being absorbed by the cells lining the small intestine. The remaining CBD is sent directly to the liver where the majority of the CBD is removed. This process is known as the first pass metabolism. Therefore, a great deal of CBD’s bioavailability is lost in this method of ingestion. A capsule is not as effective as a full spectrum CBD tincture oil that is absorbed into your bloodstream.

Keep in mind, oral ingestion is still effective just slower acting, takes a little longer and requires a great deal more CBD. This is due to approximately 90+% or so removed through the liver. Some have recommended utilizing coconut oil along with ingesting CBD as it helps to increase the CBD absorption.

Normally, less than 10% of the CBD reaches your bloodstream if you do edibles/capsules. For that reason, the best thing to do to ensure you get the highest level of bioavailability from oral administration is to hold it in your mouth for a period of time in order to increase its bioavailability.

The fastest and most direct absorption occurs under the tongue by the capillaries of the mucous membrane by what is known as a sublingual tincture.

Sublingual CBD

Taking CBD Sublingually means absorbing the CBD under the tongue which is known as a tincture and has been documented at a bioavailability rate of 35%.  Here, CBD oil is placed in the mouth moving it around with the tongue and is absorbed by the sublingual glands.

I educate my patients that it is best to hold the CBD in the mouth for 5 minutes. This allows maximum absorption by the sublingual glands under the tongue. From there the CBD goes straight to your bloodstream through the oral mucosa. After a 5-minute timeframe it is suggested to swallow the remaining contents for it to pass into the digestive tract for further absorption. This reduces the amount of CBD that has to pass through the liver and allows more of it to enter directly into the circulatory system.

Taking a CBD oil through ingestion takes a bit longer and lasts longer however, taking it sublingually helps it to act faster. Most people who are taking their CBD oil as a tincture sublingually do so at least 2 times a day: once in the morning, and once in the evening.

Vaping CBD

Vaping CBD is faster to act but won’t work for a long period of time. A lot of people recommend vaping to deal with symptoms of anxiety due to its quick effect. This form of delivery of CBD has a bioavailability of 40%. By directly entering the lungs, the CBD can then quickly and directly enter the bloodstream, with decreased breakdown rates and higher bioavailability.

You can mix an isolate into regular vape juice, but it depends on the Vegetable Glycerin (VG)/Propylene Glycol (PG) ratio. You want a ratio higher in PG because an isolate CBD doesn’t mix well with VG.

Some people like CBD tincture oil better over vaping as you know exactly how much you are dosing, whereas vaping CBD is not so clear.

Intranasal CBD

A research study conducted at the University of Kentucky found that the intranasal delivery of CBD was absorbed within 10 minutes and had a bioavailability of up to 46%.

An important point to understand is that with the intranasal absorption of CBD, as it enters the nasal passage it is absorbed by two different nerves, the olfactory and trigeminal nerves.

Therefore, the intranasal CBD has a direct path to the brain allowing it to have more of a neurologic effect to the body.

Transdermal CBD

Transdermal CBD is different from topical CBD. These are products also applied to the skin, but it actually absorbs into the skin, penetrating through, and into your bloodstream on a long term sustained delivery over time.

This means it does not only work in a localized area as a topical does but also throughout your whole body.

It takes specialized emulsifiers and chemical compounds to make a CBD product transdermal, which is also why it tends to be more expensive. Anyone can make a topical. Not just anyone can make a transdermal, at least not safely.

CBD Suppositories

CBD Suppositories are normally administered rectally but can also be vaginal. The benefit of a rectal route is an increased bioavailability, so more effect with using less.

In the case of nausea and vomiting the rectal route allows a person to still get CBD into their system in spite of not being able to hold things down in the stomach. Using CBD rectally generally takes effect in about 10 minutes.

Topical CBD

Keep in mind, topical and transdermal CBD are two completely different applications. Topicals are what 90+% of the products on the market are, such as salves, balms, roller balls, lotions, etc.

Topicals are applied to the skin but they only work on the skin. They generally only work on the top 3 layers of the skin, and it’s surrounding area, and that’s it. They do not penetrate through the skin, nor does any of the CBD get into the bloodstream.

If you take your sublingual CBD oil and apply it to your skin, that is actually a topical, not transdermal. CBD can’t be applied as a topical cream and expect it to do anything in other areas of the body as it will not travel into the circulation.

This is largely why you can apply THC topically as well, and not experience any psychoactive effects, nor will it be likely to trigger a positive drug test.

How to Increase Bioavailability?

Some people recommend using turmeric, pepper, or some other sort of oil, to increase the bioavailability of their CBD oil. Some studies have shown that using long-chain triglycerides (LCT) or medium-chain triglycerides (MCT) may increases the percentage of CBD’s bioavailability. So basically, if you want to swallow your CBD in capsules or other forms of oral ingestion do it with long chain fats like coconut or sesame oil. You’ll get 20-30% bioavailability vs. 8%-12% in non-oil formulations which is more than double what other sources have cited for oral delivery.


Preferred Delivery Method

When it comes to a tincture, most recommendations suggest holding it in the mouth for 10-30 seconds which greatly reduces the bioavailability of the CBD as it has very little time to be absorbed by the sublingual glands, which is the whole idea of a tincture. Therefore, I recommend the CBD tincture to be held in the mouth swishing it around for up to 5 minutes in order to reach its maximum absorption capacity.


Here are the most common methods of taking CBD oil and their respective bioavailability’s:

  • Oral CBD: Approximately 6%[1]
  • Sublingual CBD: 35%
  • Vaping/Inhalation CBD: 40%
  • Intranasal (IN) CBD46%  [2]
  • Transdermal CBD: 70%
  • CBD Suppositories: 90%
  • Topical CBD: Does Not Apply


  1. ^ World Health Organization (WHO) (Geneva, 4-7 June 2018) CANNABIDIOL (CBD) Critical Review Report. (PDF) Expert Committee on Drug Dependence Fortieth Meeting. pp 11 Section 4B
  2. ^ University of Kentucky (05 Nov 2010) Cannabidiol bioavailability after nasal and transdermal application: effect of permeation enhancers.