Bioavailability
The fraction of an administered dose that reaches systemic circulation unchanged. Subcutaneous injection provides 65–95% bioavailability for most peptides; oral bioavailability is typically below 1% without absorption enhancers.
Frequently Asked Questions
What is Bioavailability?
Why is Bioavailability important in peptide research?
Related Terms
The fraction of an administered dose that reaches the general circulation and is available to exert its effects throughout the body. Intravenous injection has 100% systemic bioavailability by definition.
First-pass metabolismThe metabolism of an orally administered peptide by the gut wall and liver before it reaches systemic circulation. First-pass effect dramatically reduces oral bioavailability for most peptides.
Subcutaneous injectionAn injection into the fatty tissue layer between the skin and muscle. The most common administration route for peptides, typically using insulin syringes. Preferred for its slow, steady absorption and ease of self-administration.
Oral administrationDelivery of a peptide by mouth in tablet or capsule form. Most peptides have poor oral bioavailability due to enzymatic degradation in the GI tract, though new formulations like oral semaglutide (Rybelsus) use absorption enhancers.