Bioavailability — What It Is & Why It Matters

You go out of your way to eat healthy foods and consume supplements to foster well-being. Presumably, you want to get some mileage out of those things — why else bear the cost or put forth the effort?

Well, there’s actually a measure of how much effect you’re getting from those substances. It’s called bioavailability.

In this post, we’ll explain:

  • What bioavailability is
  • How bioavailability impacts you
  • Why bioavailability is important, especially when it comes to your CBD
  • And more!

Get ready to absorb critical info!

What is Bioavailability: The Basics

Bioavailability is the degree to which a substance — like a drug, supplement, or nutrient —reaches the bloodstream after being introduced into the body (e.g., by ingesting or inhaling). Often expressed as a percentage, bioavailability indicates how much of a substance is actually absorbed into and used by your system and the rate at which it does so.

The Different Types of Bioavailability

There are three types of bioavailability:(1)

  • Absolute bioavailability is the percentage of a substance that's absorbed into or circulating through the bloodstream.
  • Relative bioavailability (and bioequivalence) is the percentage of a substance that's absorbed into or circulating through the bloodstream from a given formulation as compared to the amount that would be absorbed if the drug were taken in a different form (e.g., sublingual vs ingested).
  • Pharmacokinetic bioavailability is how well a substance is absorbed and metabolized in the body.

Bioaccessibility & Bioavailability

You can predict a substance’s bioavailability by assessing its bioaccessibility.(2) Bioaccessibility is defined as the total amount of a substance that enters the body and that is available for potential absorption.

The greater the bioaccessibility, the greater your prospects for better bioavailability. It’s like you’re working with a bigger pool of material.

So, to illustrate, if you consume 25 mg of a substance but only 20 mg actually assimilates into your body — that substance is only 80% bioaccessible. (The remaining bit — 5 mg — is inaccessible for one reason or another.) This means that even if this substance were 100% bioavailable, you’d only be able to get 20 mg of the active substance from that original 25 mg.

Calculating Bioavailability

Figuring out bioavailability requires doing some simple math. You can convey bioavailability as a percentage or a proportion.

For example, let's say you're taking a drug that’s 60% bioavailable. That means that 60% of the drug will actually make its way into your bloodstream and start doing its job. The remaining 40% will likely be eliminated by your body before it has time to do any good.

Bioavailability can also be expressed as a ratio of the dose taken. So, if you take a 100mg dose of a supplement, 60 mg will make it into your bloodstream (60/100), while 40 mg will not (40/100).

Bioavailability Influencers

Bioavailability can be affected by a variety of factors.(1,3,4) This includes a number of personal attributes like your:

  • Age
  • Gender
  • Weight
  • Health conditions
  • Microbiome
  • Stomach’s pH
  • Sleep cycles and quality
  • Metabolism

Lifestyle choices can also impact bioavailability. These are things like:

  • Your diet
  • How physically active you are
  • If you take the substance in a fed or fasted state

Last, but not least, there are plenty of physiochemical properties that can influence bioavailability, such as:

  • Medication interactions
  • Formulation
  • Size of the substance’s particles
  • Administration method
  • Manufacturing processes
  • Dosage
  • First-pass effect

Anything that runs through the gastrointestinal system — like CBD edibles and supplement capsules — will have less bioavailability than if it went directly into the bloodstream. This is because the substance is processed and affected by the liver before circulating through your body.

Why is Bioavailability Important?

Knowing a substance's level of bioavailability can give you an idea of its likely magnitude of biological activity. Bioactivity refers to how effective a substance is at doing what it's supposed to do: helping your body function properly.

This measure can help you understand how well a given drug, supplement, or nutrient is working and whether it's worth taking again. A more bioavailable substance will be faster-acting and/or yield more effect per dose than a less bioavailable substance. In fact, a low-bioavailability substance may barely make it into your system at all!

For instance, if your aim is to get 10 mg of a drug into your bloodstream, it could be better to take 20 mg of a 50% bioavailable drug than 100 mg of a 10% bioavailable drug.

To be clear, this is a call that needs to be made based on the situation at hand. But, the point is that there may be other options on the table that you should consider. Ones that could be much more likely to work effectively and safely for you.

Maria Calabrese, Founder of Green Bee Life, trying a HOLISTIK Wellness CBD & Collagen drink mix. The mix is water-soluble for greater bioavailability.

CBD & Bioavailability

Let's narrow our focus a bit now and look at bioavailability as it relates to CBD.

When CBD is consumed, it enters your body either directly into the bloodstream or via the digestive system (and then into your bloodstream from there). The bioavailability of CBD plays a role in how quickly and to what extent your body is able to process and utilize the cannabidiol.

So, what can you expect from a CBD oil product with greater bioavailability?

  • You'll likely notice the onset of effects sooner. For example, instead of waiting 90 minutes to feel something, it may take just 15 minutes.
  • Because it's kicking in more quickly, your CBD effect may peak faster or end sooner. This is largely dependent upon the type (isolate, broad-spectrum, or full-spectrum) and formulation (e.g., tincture or gummies) of CBD you take.
  • Your CBD will probably be more effective and efficient for a given amount. Mg for mg or mL for mL, you're deriving more goodness from your CBD.
  • You'll get more bang for your CBD buck. It may not take as much CBD to achieve desired outcomes — using less means buying less.

While all cannabinoids interact with endocannabinoid system receptors in the body, CBD has been shown to have particularly strong interactions with CB1 receptors. This means that — the more bioavailable the CBD is (5) the more it can influence its effectiveness at providing relief from conditions like chronic pain and other desired outcomes.

CBD bioavailability can also affect whether or not you experience side effects from taking CBD oil products.(6)

The Bioavailability of CBD

It’s impossible to nail down an “average bioavailability” of CBD. So, let’s see what some of the scientific literature is reporting.

Here are some numbers to mull over for different formulations and methods of administration:(8,9,10,11)

  • Vaped CBD (inhaled). 56%
  • Smoked CBD (inhaled). 31-45%
  • Rectal CBD (suppositories). 13-40%
  • Buccal/Oromucosal CBD (via the cheeks or gums). Greater than sublingual
  • Sublingual CBD (under the tongue). 19-35%
  • Intranasal CBD (via the nose). 34-46%
  • Oral CBD (ingested, including edibles). 6-20%
  • Transdermal CBD (through the skin barrier). Unknown (not studied yet)
  • Topical CBD (applied externally). 3%*

Injected CBD has a bioavailability of almost 100%. However, intravenous CBD is only done in medical settings by qualified professionals as it can be dangerous to consume CBD intravenously. In animal studies, this method of administration sometimes caused sudden high levels of CBD in the bloodstream, which can result in dangerously low blood pressure.(12)

* To clarify, this is not saying topicals are or aren’t effective. It’s simply indicating that the CBD from topicals doesn’t leach into the bloodstream much. Which is just how topical CBD is supposed to work.

Maximizing the Bioavailability of Your CBD Oil Products

CBD is available in various formulations — gummies, tinctures, softgels, etc. — and can be taken in several ways — ingested, intranasally, topically, etc.

As we’ve shown, the bioavailability of CBD is strongly influenced by the form, concentration, and consumption method. Each preparation and administration protocol translates into different levels of bioavailability. And, therefore, the necessity to adjust the strength and dosage of the product you take as well.

The Most Bioavailable CBD Is...

It’s important to choose a delivery system that will allow for optimal absorption and avoid any resistance from the body. For example, using sublingual CBD oil drops allows for quick and easy absorption into the bloodstream.

Which leads us to the most bioavailable forms of CBD oil. Inhaled CBD is reportedly the most bioavailable. However, there are health risks associated with smoking and vaping. If you’re concerned about lung health, sublingual or intranasal varieties of CBD — like CBD tinctures — are probably going to be your go-tos. These formulations are designed to enter directly into the bloodstream.

Improving the Bioavailability of Your CBD

There are other tips and tricks to making your CBD more bioavailable. You can try:(13)

  • Using sublingual or intranasal CBD
  • Try water-soluble formulations
  • Consuming CBD on a full stomach
  • Taking your CBD with a snack or meal that has some fat in it
  • Using full-spectrum CBD or broad-spectrum CBD that has other cannabinoids, terpenes, and flavonoids
  • Supplementing with complementary compounds, like pepper and turmeric
  • Finding CBD products that leverage technology (e.g., nanotechnology or liposomal encapsulation)(14,15)

Absorb This: Bioavailability’s a Good Thing, Especially for Your CBD

Bioavailability refers to how absorbable a substance is. Absorbability impacts how quickly and fully that substance can enter your body and be effective.

Generally speaking, greater bioavailability is desirable when it comes to nutrition, plant medicine, or any other instance in which you’re trying to derive benefit from that substance.

FAQs Buzzin’ Through the Hive

What is bioavailability?

Bioavailability is the proportion of a substance — like CBD — that’s introduced to your body that your body is able to absorb and utilize.

How do you increase CBD absorption?

Start by taking high-quality full-spectrum CBD or broad-spectrum CBD that has plenty of terpenes and flavonoids in it, ideally sublingually or intranasally. Consume your CBD with food, especially those that contain healthy fats and complementary compounds like pepper and turmeric.

What is the bioavailability of CBD?

It depends on the formulation and method of administration. On the high end of the spectrum are inhaled and sublingual CBD; topical and ingested CBD are on the lower end.


  1. Choudhary, A. (2022). Bioavailability of Drugs. Pharmaguideline.
  2. Galanakis, C. (2017). What is the Difference Between Bioavailability Bioaccessibility and Bioactivity of Food Components? SciTech Connect. Elsevier.
  3. (2022). Bioavailability. Wikipedia.
  4. Choudhary, A. (2022). What factors affect the bioavailability of drugs? Pharmaguideline.
  5. Vučković, S, et al. (2018). Cannabinoids and Pain: New Insights From Old Molecules. Frontiers in Pharmacology.
  6. Huestis, MA, et al. (2019). Cannabidiol Adverse Effects and Toxicity. Current Neuropharmacology.
  7. Millar, SA, et al. (2020). Towards Better Delivery of Cannabidiol (CBD). Pharmaceuticals.
  8. Millar, SA, et al. (2018). A Systematic Review on the Pharmacokinetics of Cannabidiol in Humans. Frontiers in Pharmacology.
  9. Huestis, Marilyn A. (2007). Human Cannabinoid Pharmacokinetics. Chemistry & Biodiversity.
  10. Paudel, K, et al. (2022). Cannabidiol bioavailability after nasal and transdermal application: effect of permeation enhancers. Drug Development and Industrial Pharmacy.
  11. Sultan, SR, et al. (2017). A Systematic Review and Meta-Analysis of the Haemodynamic Effects of Cannabidiol. Frontiers in Pharmacology.
  12. (2021). 7 foods to elevate the effects of CBD supplements. The Guardian.
  13. Conte, R, et al. (2017). Recent Advances in Nanoparticle-Mediated Delivery of Anti-Inflammatory Phytocompounds. International Journal of Molecular Sciences.
  14. McCabe, K. (2019). Using liposomes to safely deliver CBD and other Pharmaceuticals. Microfluidics.
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About the Author

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GBL Staff Writer

Green Bee Life is your resource for accurate, transparent, and up-to-date content and products related to cannabis.

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