Bioavailability is the percentage of a drug that actually reaches your bloodstream and becomes available to work in your body. When you swallow a pill, not all of it makes it into circulation. This publication discusses the basic concepts of bioavailability and the factors affecting it. We also looked at various methods of assessing bioavailability, both in the laboratory and in the clinic. Bioavailability refers to the extent and rate at which the active moiety (drug or metabolite) enters the systemic circulation, thereby accessing the site of action. Bioavailability (F) describes the fraction of a dose of drug that reaches the systemic circulation. Bioavailability of a single drug may vary significantly depending on the route of administration. This Research Topic is aimed to collect research work related to systemic studies of bioaccessibility, bioavailability, and the bioactive properties of bioactive molecules, as well as the strategies to enhance them in favor of human health. In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. [1] Bioavailability (BA) refers to the fraction of an administered dose that reaches systemic circulation in its active form. It describes both the rate and extent of absorption.