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CBD Bioavailability: How the body absorbs and utilizes cannabidiol

Not all CBD products are created equal. Some provide instant relief while others are not as effective. Whatever your intent in consuming CBD, you need to know about bioavailability.

What is bioavailability?

What is bioavailability?

According to the American Heritage Medical Dictionary, bioavailability is the degree to which a drug or other substance becomes available to the target tissue upon administration. It is the percentage of the compound that is absorbed into the bloodstream after it is fully processed by the body. Knowing the bioavailability of your CBD product helps you choose the right one for your health and wellness goals. [R]

Intravenous administration is considered 100% bioavailable because the substance is injected directly to the bloodstream. This means that if you take CBD through an IV dose, 100% of the CBD is actively available. Other methods of administration are measured against the intravenous route as a ratio for the bioavailability percentage.

The most popular forms of CBD are tinctures, vaping oils, capsules and pills, topical creams, and edibles – each with a different bioavailability level. How you consume CBD determines how much of the substance actually gets used by your body.

What is CBD bioavailability?

What is CBD bioavailability?

Cannabinoids can be delivered in many ways, depending on user requirement and preference. In the medical practice, the comfort level of the patient plays an important factor in prescribing practices. With CBD, effectiveness should be prioritized over comfort. The route of administration can have a more pronounced effect in treating a symptom in a particular site of action.

The medical dictionary defines route of administration as the path by which a substance is taken into the body. This can be by mouth, on the skin, in the rectum, or directly into the blood. The route of administration of CBD is extremely important in determining the uptake and distribution of the substance in order to achieve the desired therapeutic effects. [R]

Bioavailability refers to the absorption of a drug or supplement from the site of administration to the bloodstream. When doctors prescribe medication, standard dosage is partly determined by bioavailability of the drug.

The high bioavailability of a dose allows you to consume CBD in lower quantities to feel the effects. High bioavailability is what makes a hemp-based product potent.

CBD bioavailability varies according to route of administration and the concentration of CBD in the product.

Factors affecting CBD bioavailability

Factors affecting CBD bioavailability

Aside from method of consumption, there are a few factors that could affect the bioavailability of CBD.

No matter what form, CBD will always be hydrophobic. This means that it does not dissolve in water. CBD adheres to fatty tissue, which reduces the actual amount that goes into the bloodstream. This is why CBD capsules and edibles have low bioavailability.

Body weight and product quality can also affect the active dosage of CBD. As with any product you put in your body, you must do research before purchasing a CBD product. Always start with a low dose and work your way up until you find your sweet spot.

What is the method of CBD consumption with the highest bioavailability?

What is the method of CBD consumption with the highest bioavailability?

While intravenous administration delivers 100% of CBD into the body, it is not the most popular option. Sticking a needle up your vein can be painful and inconvenient.

We have summarized five different routes of administration for CBD and how each one affects bioavailability.

Oral ingestion

Oral ingestion

The most common method of consumption of CBD is ingestion through the mouth. This is the easiest way to take CBD as oils, capsules and edibles are readily available and can be incorporated into many food products.

Oral CBD comes in bottled oil or a standard capsule full of CBD powder. It can be swallowed with or without food.

Any substance consumed through the mouth will have to pass through the metabolic and digestive systems. When this happens, the CBD is metabolized by the gastrointestinal tract and liver and creates a first-pass effect.

Before the CBD reaches the circulatory system, enzymes in the gut wall and liver break down the CBD which reduces its concentration significantly before sending the leftovers into the bloodstream. [R] [R]

The first-pass effect effectively prevents the absorption of cannabinoids into the blood which explains why CBD gummies and other edibles have the lowest percentages of CBD bioavailability. Sometimes even after waiting more than an hour after ingestion, you feel nothing.

Participants in a 1986 study consumed chocolate cookies with 40mg of CBD. The results showed only a 6% bioavailability rate. A more recent study conducted in 2009 reported oral CBD bioavailability between 4% and 20%. In a pharmacokinetic study performed on dogs, CBD had a higher oral bioavailability of 13% to 19%. While these findings differ significantly, all are pretty low compared to other routes of administration, with a 20% bioavailability rate being the most optimistic scenario. [R] [R]

In a clinical trial conducted on patients with Huntington’s disease, oral CBD also showed very low bioavailability levels. CBD was present in low concentrations in the blood plasma and within a relatively narrow range. Among 14 patients, the mean levels ranged from 5.9ng/ml to 11.2ng/ml. [R]

With 20% bioavailability, eating a CBD gummy that contains 100mg of CBD means only 20mg of the substance will actually reach your bloodstream.

Apart from inefficient absorption, another issue with oral CBD is that it can take as long as two hours to work. The good news is that despite their low bioavailability, CBD edibles produce effects that may last longer.

There are a number of ways to increase the bioavailability rate of oral CBD.

In a 2009 study published by the U.S. National Library of Medicine, research suggests that swallowing CBD with fatty acids may bypass the first-pass effect and increase absorption rates of CBD after ingestion. [R]

Long-chain triglycerides or fatty acids can help bypass the first-pass metabolism in the liver. The proposed mechanism for this is through the left internal jugular and left subclavian veins in the intestinal lymphatic system, bypassing the liver in the process. [R]

Another way to improve bioavailability is to simply take a higher dose of CBD oil.

CDB is able to reach the bloodstream faster if you take it sublingually. This means holding it under the tongue for a few minutes before swallowing. The mucus membranes of the mouth will absorb the CBD instead of going through the digestive system – bypassing the liver entirely.

Sublingual drops

Sublingual drops

Sublingual delivery of CBD refers to placing the oil under your tongue. The sublingual gland, a vein under the tongue, enables direct absorption of CBD into the bloodstream. The sublingual route of administration bypasses first-pass metabolism when CBD is absorbed by the capillaries below the tongue. [R]

The bioavailability of consuming CBD sublingually has reported rates of 12% to 35% which is significantly higher than oral consumption. [R]

A 2007 study performed on rabbits compared the bioavailability of oral and sublingual CBD solutions. Results showed that sublingual CBD had significantly higher bioavailability than oral CBD. [R]

Because sublingual consumption transfers the CBD into your blood more directly, it takes effect faster than oral consumption. It also maintains higher availability as the compound is only degraded by saliva. Most people feel the effects from a sublingual CBD dose within 20 minutes.

When it comes to comfort, the sublingual route of administration is on par with the oral route. Sublingual CBD is available in tinctures, lozenges, strips, tablets and sprays.

Smoking and vaping

Smoking and vaping

According to a clinical study, the psychoactive effects of THC are felt faster when inhaled than taken orally. The bioavailability of THC after inhalation was estimated to be at 18% whereas THC in a chocolate cookie had 6% bioavailability. Since THC and CBD are similar in lipophilicity, bioavailability data correlates between the two. [R] [R]

The high bioavailability of inhaling CBD may be attributed to the fact that the lungs have a large absorptive surface area, high permeability, and good blood supply for CBD to enter the circulatory system. It bypasses first-pass metabolism in a similar way as sublingual administration except vapor reaches the bloodstream faster.

A key observation from this study was that the clinical effects of oral administration had a slower onset but lasted for a longer period of time. While the inhaled route had a faster onset, the rapid elimination of CBD resulted in shorter lasting effect.

Like smoking, vaping utilizes the lungs to absorb CBD. It has fewer harmful side effects because you are inhaling vapor and not smoke. Decarboxylation is required to activate cannabinoids, and a vaporizer does this by heating the compound to a certain temperature. In contrast, smoking uses combustion to ignite a joint.

Inhaling CBD-infused vapor is one of the quickest ways to deliver CBD into the bloodstream. During this process, the CBD enters the lungs and passes through tiny air sacs called alveoli. CBD travels through the thin walls of the alveoli and goes directly into the bloodstream with decreased breakdown rates.

Numerous medical studies report that the bioavailability rates of vaping CBD is around 34% to 46% or even as high as 56%. [R] [R]

In a 2016 study of medical cannabis entitled In Vitro Validation of Vaporizers for the Smoke-Free Inhalation of Cannabis, the potential to dramatically increase the bioavailability of cannabis with vaping was established as a fact. The research focused on both THC and CBD and found that vaping is the best way to dose on each substance. [R]

CBD bioavailability after inhalation was found to have a mean value of 31% which is significantly higher than ingesting CBD. [R]

If you are suffering from an acute condition such as pain and anxiety, and you need relief right now, having 40% to 50% available CBD at your fingertips is great news. But in chronic situations, vaping may not be the best option as the effects easily wear off.

Of course if you are administering CBD to children or pets, vaping is a no-no.

Vaporized CBD may be the best in terms of bioavailability but it should only be used in certain instances.

Topical CBD

Topical CBD

CBD-infused skincare products are hot right now. You can find CBD in almost any topical formula – creams, lotions, balms, rubs, lubes and more. This route of administration has no psychoactive side effect. Even if your cream contains THC and you liberally rub it on your skin, it cannot get you high. Cannabinoids are hydrophobic and the skin acts as a barrier that prevents THC or CBD from reaching the bloodstream.

Topical CBD products are designed to deliver targeted relief to a specific area. The skin has several cannabinoid receptors that absorb and interact with CBD when it is applied to the surface.

Do note that absorption rates are very low so you need to smear topical CBD products generously for them to work. Also, make sure your topical salves contain very high levels of CBD to achieve desired results.

The only form of topical CBD that is able to penetrate the skin and enter the bloodstream is the transdermal CBD patch. By definition, transdermal means crossing the skin barrier to reach the blood. [R]

Rectal suppositories

Rectal suppositories

The rectal route of CBD administration is not the most popular but it is effective in cases where oral delivery is not possible. Once such scenario is when patients have trouble swallowing or are suffering from nausea and vomiting.

According to data from pharmacokinetic studies, the rectal route of administration of THC approximately doubles the bioavailability of oral delivery. Out of the three veins in the venous drainage of the rectum, only the superior rectal vein connects to the liver so there is only a partial first-pass metabolism effect. The bioavailability of THC from a rectal formulation is found to be 13.5% which explains why suppositories have a faster onset of action than oral CBD forms. [R] [R]s

In a 2012 study, researchers compared the effects of oral CBD and rectal CBD administered to mice induced with colon inflammation. Results showed that rectal CBD significantly reduced inflammation in the rectum whereas oral CBD had no effect. [R]

Rectal and intravenous routes of CBD administration deliver CBD into the bloodstream very quickly because of the method of absorption. Suppositories send CBD through mucous membranes while needles directly inject CBD into the blood. However, they are the least popular forms of CBD administration since nobody wants to inject CBD or insert suppositories unless the patient is severely ill.

Inhalation vs. ingestion

Inhalation vs. ingestion

In a study published in the US National Library of Medicine, researchers compared three routes of cannabinoid administration: oral, inhaled and intravenous. They found that the oral route provided the longest period of clinical effects despite producing the lowest plasma concentration. [R]

Although inhaling CBD can provide a more rapid onset, it also has a shorter clinical effect. It begins to clear after approximately one to three hours. This is due to the fact that the plasma concentrations peak extremely fast and CBD is quickly eliminated from the bloodstream.

In the oral route of administration, CBD is slowly released into the bloodstream. It maintains low concentrations of CBD in the blood over a period of around seven hours and is eliminated at a slower rate.

To give you an idea how CBD edibles and CBD vapor differ, let's say you purchased a 500mg CBD edible for $50 and a 500mg CBD e-liquid for the same price.

With a bioavailability rate of roughly 10% in CBD edibles, 50mg of CBD would enter your bloodstream which means you would be paying $1 per milligram of CBD.

With a bioavailability rate of around 35% in CBD e-liquids, 175mg of CBD would enter your bloodstream which means you would be paying $0.28 per milligram of CBD.

That translates to 72% cost savings from vaping CBD than eating CBD edibles!

Now multiply that to a year of consumption. If you take 1,000 milligrams of CBD per month, or 12,000 milligrams of CBD per year, you would be spending $12,000 on edibles compared to just $3,360 on vapes.

CBD bioavailability of isolate vs. full-spectrum

CBD bioavailability of isolate vs. full-spectrum

The cannabis plant has more than 100 cannabinoids. CBD is just one of them. Scientists have found ways to isolate CBD from the rest of the pack – a product now known as CBD isolate. This compound is more stable and completely THC-free.

While pure CBD has plenty of benefits, some experts believe that combining CBD with other cannabinoids theoretically improves the bioavailability and efficacy of the CBD. These products are called CBD full-spectrum and are often associated with the entourage effect.

Trace compounds in cannabis interact synergistically to create an entourage effect – a term coined by scientists to describe the amplified therapeutic benefits of each individual component in a plant. This entourage effect makes the medicinal impact of a whole plant greater than the sum of its parts.

Here are some of the known cannabinoids and their potential benefits to living systems:

CBD benefits

  • Antibacterial
  • Inhibits cancer cell growth
  • Neuro-protective
  • Promotes bone growth
  • Reduces seizures and convulsions
  • Reduces blood sugar levels
  • Reduces inflammation
  • Reduces risk of artery blockage
  • Reduces small intestine contractions
  • Reduces vomiting and nausea
  • Relieves pain
  • Relieves anxiety
  • Slows down bacteria growth
  • Suppresses muscle spasms
  • Tranquilizer effect
  • Treats psoriasis
  • Vasorelaxant

CBDA benefits

  • Reduces inflammation
  • Inhibits cancer cell growth

CBG benefits

  • Aids sleep
  • Inhibits cancer cell growth
  • Promotes bone growth
  • Slows down bacteria growth

CBGA benefits

  • Reduces inflammation
  • Relieves pain
  • Slows down bacteria growth

CBC benefits

  • Inhibits cancer cell growth
  • Promotes bone growth
  • Reduces inflammation
  • Relieves pain

CBCA benefits

  • Reduces inflammation
  • Treats fungal infection

THCA benefits

  • Aids sleep
  • Inhibits cancer cell growth
  • Suppresses muscle spasms

THC benefits

  • Reduces vomiting and nausea
  • Relieves pain
  • Stimulates appetite
  • Suppresses muscle spasms

THCV benefits

  • Reduces convulsions and seizures
  • Promotes bone growth

By understanding how CBD bioavailability works, you can choose the most effective CBD product for your symptoms and not overspend on methods that do not work.

What is the best route of CBD administration?

What is the best route of CBD administration?

Balancing bioavailability and convenience, the sublingual and inhalation routes are the most efficient ways to deliver CBD into the bloodstream if your symptoms require quick relief. For chronic ailments, oral CBD can produce effects that last longer.

Keep in mind that there is no one-size-fits-all solution when it comes to supplementing on CBD. There is no right or wrong way to take CBD. The various routes of administration should be applied in situations where they are most effective.

If comfort is a priority, oral administration is the easiest way to treat symptoms. Oral CBD is ideal in situations that require a small concentration of CBD in the circulatory system for a longer period of time.

The bioavailability rate of CBD edibles is low, but that can be resolved by combining CBD with fatty acids or taking CBD at a higher dosage. Another way to improve the bioavailability of oral CBD is to take it sublingually. CBD tinctures have increased absorption rates when placed under the tongue.

If you feel an anxiety attack coming, inhaling CBD is the fastest way to achieve relief. The downside to vaping CBD is that some ingredients in the e-liquid may be harmful to your lungs and throat. The therapeutic effects of vaping are also short-lived.

Rectal CBD administration can be incredibly effective as the CBD bypasses the digestive system and reaches the bloodstream quickly. It has shown potential in treating colon diseases by reducing inflammation. With high bioavailability, suppositories can deliver a higher concentration of CBD to the target area in the body.

Talk to your doctor before you start taking CBD. The route of administration you choose will depend on the bioavailability of the CBD product and specific symptoms you aim to treat.


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