Glossary entry
Bioavailability
Definition
The proportion of a drug that reaches systemic circulation in active form. Injectable GLP-1s (Wegovy, Mounjaro) have higher bioavailability than oral semaglutide (Rybelsus).
Related terms
A1C (HbA1c)
A blood test that measures average blood glucose over the past 2-3 months. A1C ≥6.5% indicates diabetes. GLP-1 medications typically lower A1C by 1-2 percentage points.
BMI (Body Mass Index)
A screening calculation of body weight relative to height (kg/m²). FDA-approved weight-management GLP-1s require BMI ≥30, or ≥27 with a weight-related comorbidity.
Compounded medication
A medication custom-prepared by a licensed compounding pharmacy, often using the same active ingredient as a brand-name drug. The FDA allowed compounded semaglutide during the 2022-2025 shortage; access has tightened since.
Comorbidity
A second medical condition occurring with the primary one. Hypertension, type 2 diabetes, dyslipidemia, and obstructive sleep apnea are common weight-related comorbidities that lower the BMI threshold for GLP-1 eligibility to 27.
Contraindication
A specific situation in which a drug should not be used. GLP-1 contraindications include personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2).
FDA prescribing information (PI)
The official drug label, including approved uses, dosing, contraindications, warnings, and clinical trial data. Located on accessdata.fda.gov. The primary citation source for every medication page on this site.