Bioavailability is the amount of a substance that the body can readily absorb and use. Different substances have differing levels of bioavailability, as do different methods of ingesting or applying those substances.
Because CBD is an oil, it is not readily absorbed by the body. In fact, when CBD is ingested and passes through the digestive system, most of it is destroyed. A World Health Organization review of CBD studies shows that bioavailability of CBD when taken orally (meaning swallowed and entering digestion) can be as low as 6% (https://www.who.int/medicines/access/controlled-substances/CannabidiolCriticalReview.pdf).
Your body processes CBD differently when it goes through digestion than it does when CBD is inhaled or applied topically, so the way you are using CBD can have a major impact to how much is actually being utilized by your body. According to www.cannabislaw.report/cbd-bioavailability, “oral CBD bioavailability ranges from about 6-15% while vaporizing can be up to 50%. Topical and transdermal products have a bioavailability rate around 45%, and nasal sprays around 40%.” Cannabinoid suppositories have been shown to have bioavailability up to twice that of products taken orally (https://pubmed.ncbi.nlm.nih.gov/8897084/).
The best way to increase bioavailability of CBD is by using a nanoemulsion, which is a blend of purified water with emulsifiers, and CBD oil broken into ultra-tiny droplets that cross into the bloodstream directly. Because Nano CBD’s small particles cross directly into the bloodstream, they absorb more readily into the body, and any Nano CBD that does make it into the digestive tract is not destroyed as readily as oil-based CBD because it is encapsulated in a bubble of surfactants. This means that almost all of the Nano CBD taken is absorbed and used by the body.