What is bioavailability and how does it affect the way you choose to take CBD? In this article, we’ll be discussing the importance of bioavailability and how delivery methods, as well as internal and external factors, can affect your body’s absorption of CBD.
Author’s note: Our articles are not a substitute for medical advice. Please consult your GP or pharmacist with any questions about CBD use. This article is for informational purposes only.
What is bioavailability?
Bioavailability is defined as the amount of a given substance which is able to enter the bloodstream when introduced into the body, allowing it to have an active effect. Essentially, the term refers to the proportion of your CBD dosage which is able to remain in circulation long enough to reach the organs and tissues you’re targeting.
Interestingly, bioavailability can vary widely depending on the method in which you take the CBD.
So, how much of your CBD dose actually gets absorbed and used by the body?
This depends on a process known as pharmacokinetics, or how a given compound is processed by the body.
Pharmacokinetics can be defined as your body’s mechanisms for absorption and elimination of compounds. Other factors which influence pharmacokinetics include the characteristics of the CBD itself, as well as external factors which can either help or hinder the way your body processes CBD.
Above all else, your chosen CBD delivery method has a significant impact on the bioavailability and pharmacokinetics involved.
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Let’s break down the various CBD delivery methods and discuss what impact they have on the bioavailability of your CBD.
Bioavailability of Oral CBD
Oral CBD—in the form of CBD edibles, capsules, and supplements—is one of the most popular ways to get your daily, longer-lasting dose of CBD. CBD taken in this form has the longest onset time of all delivery methods, but it also lasts the longest in your system.
However, orally ingested CBD has the lowest bioavailability of all delivery methods at just 6-19%. This means that of any given dose of CBD you take orally, your body only absorbs between 6-19% of the total dose.
One primary reason for this is that CBD isn’t readily absorbed when ingested, which leads to most of it being excreted without any effects. This is because CBD is fat-soluble, as opposed to water-soluble, which is harder for the body to absorb. Plus, the digestive acids and enzymes in your gastrointestinal tract end up destroying much of the CBD before it has a chance to be absorbed.
Still, the low bioavailability of oral CBD is offset by some of its advantages, such as its longer duration. One study found that peak levels of CBD in the blood were achieved between 1.5 and 3 hours after ingestion.
So, while bioavailability is low in oral CBD, there are certain important advantages to using this delivery method, particularly for those who are looking for relief from a chronic issue, like pain disorders or low mood.
Bioavailability of Inhaled CBD
CBD vapes and smoked CBD herb have the fastest onset time of any delivery method. Whereas oral CBD takes 1.5 to 3 hours to reach peak levels in the blood, inhaled CBD reaches peak levels in just 3 minutes.
Vaping is a highly efficient way of consuming CBD, as it bypasses the digestive tract and liver and is instead readily absorbed into the thin membranes lining the lungs. From here, the CBD enters the bloodstream directly. This allows the user to absorb more of their CBD dose than if the CBD was ingested orally.
The bioavailability of inhaled CBD is roughly 31%, give or take—and this is notably much higher than oral CBD’s bioavailability.
Still, this delivery method has its downsides, depending on your reasoning for taking CBD. If you’re simply using CBD to help with focus, alertness, or managing stress throughout the day, inhaled CBD is an excellent choice—but if you’re hoping to relieve a chronic problem, you may want to consider another delivery method (or supplement a secondary method on top of simply vaping CBD).
This is because inhaled CBD wears off quicker than other delivery methods. So, while inhaled CBD has a high bioavailability and is able to bypass some of the hurdles our bodies face when processing CBD, it doesn’t last as long (roughly 1 to 3 hours).
Bioavailability of Sublingual CBD
Perhaps the most popular method of ingesting CBD is via CBD oral drops, oils, and tinctures. This method requires the user to place drops of the CBD oil under the tongue, hold it there for about a minute, then swallow the leftover oil.
This delivery method is popular because it’s a middle-ground as far as onset time and duration is concerned. Peak blood levels of CBD with this delivery method are usually reached within 2 hours.
CBD taken this way is absorbed by the mucous membranes in your mouth, which again bypasses the digestive tract for a quicker and more efficient CBD dose. The bioavailability of sublingual CBD is roughly 35%, which is slightly higher than inhaled CBD. Plus, this method has a longer duration than inhaled CBD at 2 to 4 hours.
The best way to maximise the bioavailability of your sublingual CBD dose is to ensure you hold the oil under your tongue for at least 30 seconds, up to one minute for maximum effect.
Bioavailability of Topical CBD
Topical CBD—in the form of a CBD lotion, salve, balm, and so on—is often used by athletes or those who have chronic pain or inflammation of the joints or muscles. This method can help with localised pain and inflammation, but the CBD doesn’t actually enter the bloodstream this way.
This is because, as we previously mentioned, CBD is highly fat-soluble. The CBD tends to be repelled by the water-soluble layer of skin.
There are some methods of topical CBD which introduce ethanol to the equation, making the CBD more water-soluble and thus able to permeate the skin and increase absorption. Still, most topical CBD products on the commercial market do not have this ingredient, so the CBD used this way does not enter the bloodstream.
Factors Affecting CBD Bioavailability
The pharmacokinetic effects of CBD can be influenced by other factors aside from the compound itself. Below, you’ll find a few of these factors influencing your CBD’s bioavailability.
Your health can affect CBD absorption significantly, and as a result, you may have to adjust your dosage or delivery method accordingly.
One condition which can heavily impact CBD’s bioavailability is an impairment of your liver function. Because the liver is so vital in removing the CBD from circulation in your body, impaired liver function can lead to your CBD dose remaining in your body at peak levels for longer. In one study, participants with moderate to severe liver impairment had higher CBD concentrations in their blood and a longer duration after the same dose compared to control subjects.
This means that if you suffer from impaired liver function, more of your CBD dose will reach general circulation and will remain in your body longer. In addition, you may experience greater effects than a healthy person taking the same dose.
Neurological disorders and other health conditions may impact your CBD’s bioavailability as well. For instance, a study conducted on Huntington’s disease patients found that participants had low peak absorption levels and few to no beneficial effects from CBD.
Research is still ongoing as to which conditions may positively or negatively affect the pharmacokinetics of CBD. When in doubt, ask a healthcare professional.
Considering our current knowledge of CBD, experts suggest that you can push for better absorption of your CBD by taking slightly higher doses. Essentially, a higher dose of CBD will lead to greater absorption.
However, there does appear to be a ceiling on this benefit. According to research, any doses above 400mg to 800mg won’t have greater absorption properties than doses below this point.
Experts believe that this may, in part, be due to the tissues in your body becoming saturated and unable to absorb more CBD beyond this threshold.
Empty vs. Full Stomach
Studies suggest that CBD absorption is significantly higher—3 to 5 times higher—when taken with food compared to taking it on an empty stomach.
Remember the whole fat-soluble conundrum you face when taking CBD orally? Well, this is the same reason it’s better to take CBD with food. Better yet, taking your CBD with foods which are high in healthy fats—including eggs, avocado, nuts and seeds, and fish high in omega-3s—will help you absorb even more of the CBD. This is because the CBD is able to dissolve in the dietary fats, dispersing into smaller particles which are easier for the body to absorb.
In addition, food can slow the rate at which CBD is removed from the body. CBD can leave the body up to 9 times quicker during a “fasted state” (in which you haven’t eaten) compared to a “fed state.”
Summary: CBD Bioavailability
Bioavailability, defined as the proportion of a substance which enters circulation and has an active effect in the body, is an important measurement of how effective your CBD dose will be.
Above all else, you should now be aware of the big role your delivery method can play in the absorption of your CBD. Here’s a quick breakdown of each method’s bioavailability:
- Oral CBD: 6 – 19% bioavailability
- Inhaled CBD: 31% bioavailability
- Sublingual CBD: 35% bioavailability
You should also be aware that a number of external and internal factors, from underlying health conditions to what you’ve eaten that day, can impact the absorption of your CBD dose.
As always, research about CBD and its effectiveness in treating certain ailments is still ongoing. When in doubt, please consult a healthcare professional—such as your GP or pharmacist—for advice on whether CBD is right for you.