What is CBD Bioavailability, and Why Does it Matter?

CBD bioavailability measures how well and how quickly your body absorbs a substance. But many oral CBD products —like capsules, gummies, or oils you add to your morning coffee or mix into a smoothie—are notorious for having low or unpredictable bioavailability. That's because CBD is an oily substance: Our bodies are around 60 percent water, and oil and water don't mix. One report estimates that the bioavailability of CBD oil is as little as 6 percent. In other words, when we take CBD oil, as much as 94 percent of it might not be absorbed.

Bioavailability solves this problem. When you ingest something that's highly bioavailable, you're absorbing all of it—or nearly all. That's why with so many forms of CBD to choose from, you'll get the most value when you pick the form that's most bioavailable. 

CBD pharmacokinetics

To understand a product's bioavailability, you need to apply Pharmacokinetics (PK)—the science of tracing the path bioactive substances (like CBD) take in the body. It reveals the differences between what we consume, what we absorb, what we excrete, and the rate and efficiency of absorption. 

Many CBD products make claims to "high bioavailability" or "better absorption" based on studies with lab animals or extrapolate from research conducted with similar, non-cannabinoid substances like curcumin (turmeric). But humans are not lab rats, and intrapersonal variability of absorption is varied enough as is. 

In 2021, researchers from Colorado State University published the first-ever human clinical study of commercially available CBD products in the medical journal Pharmaceuticals special issue. The study was a breakthrough in our understanding of the pharmacokinetics of CBD. Researchers followed rigorous protocols: The study was double-blind, meaning neither the researchers nor the subjects knew which products they were being given. It also used a crossover design. Each participant received each product in random order, and each served as their control, ensuring that the results accounted for the differences in people's body chemistries.

The study observed the impact of many CBD edible formulations on pharmacokinetics — if you're not absorbing it, you're not getting its benefits. CBD in its native form is hydrophobic. It does not dissolve in water. However, CBD can be converted into water-soluble formats when adequately mixed with food-grade emulsifiers. The study was designed to ascertain the absorption differences between water-soluble and fat-based edible formats and the impact of product design within different water-soluble formulations.

The differences in CBD absorption between the different formulations was astonishing.

For example, the water-soluble CBD formulations from Caliper absorbed much faster and much more significantly in all three product formats tested. How fast? Measurable within 10 minutes, with peak absorption concentrations (Cmax) ranging from 45 to 90 minutes. The total amount of CBD absorbed over 4 hours (AUC) was quantified for comparison.  

All water-soluble formulations were processed to form "nanoemulsions." A nanoemulsion is one-billionth of a meter — it's tiny. An average hair is 100,000 nanometers wide. The conventional thinking is that smaller is better for nanoemulsions to transport from your small intestines into your bloodstream. But the study proved that smaller wasn't necessarily better—the best formulation also had the largest emulsion fingerprint.  

Why was this the case? Because formulation matters, including which emulsifiers are incorporated. There is only one way to truly know how a product will be absorbed by a human, and that's to measure it in humans.

So what about the fat-soluble CBD? The researchers investigated both CBD in MCT (Medium Chain Triglycerides) carrier oil and CBD in its purest form, CBD isolate. Both fat-soluble CBD formats took a long time to get into the bloodstream and were absorbed at a much lesser amount after four hours. For the first 60 minutes, almost no CBD was absorbed into the bloodstream. Peak absorption wasn't until 2 hours or longer, with significantly lesser amounts than any double water format.

What does this all mean?

Many popular CBD formats in the marketplace may not provide the benefits consumers want. The products are either taking too long to work or just not being absorbed enough to make an impact. Who wants to wait 2 hours to feel the effect? Consumers demand products that deliver benefits in a predictable, timely manner. Having clinical research and human studies to back claims is a step toward creating cannabinoid-based products that are more likely to provide consumers with tangible benefits. CBD formulation design matters.