Bioavailability

Bioavailability is the fraction of an administered amount of a substance that reaches the bloodstream unchanged and is available to act in the body.

An intravenous dose is defined as one hundred percent bioavailable, and every other route is measured against it. Swallowed compounds must survive stomach acid, be absorbed through the gut wall, and pass through the liver before reaching general circulation, so their bioavailability is typically lower. Researchers estimate the figure by comparing the area under the concentration-time curve for a given route against the intravenous reference.

Cannabidiol is fat-soluble and poorly water-soluble, and published studies report that oral bioavailability is low and highly variable, with fatty meals and oil-based carriers raising exposure. Formulation techniques such as nanoemulsions and liposomes are marketed as ways to improve bioavailability, but the claims need product-specific data. Readers meet the word in product marketing and study abstracts. A higher bioavailability figure means more of the compound reaches the blood; it says nothing about whether that produces a particular effect.