What It Is
Semaglutide is a synthetic analog of glucagon-like peptide-1 (GLP-1), an incretin hormone the body releases after eating to help regulate blood sugar and appetite.[1] Structural modifications — including a fatty-acid side chain that promotes albumin binding and resistance to enzymatic breakdown — extend its half-life to roughly a week, supporting once-weekly dosing in injectable form.[2]
Semaglutide is the active ingredient in three FDA-approved prescription products: Ozempic and Rybelsus for type 2 diabetes, and Wegovy for chronic weight management, each with its own approved indication, dose, and label.[3] This approved pharmaceutical status is distinct from the unapproved, compounded, and "research peptide" semaglutide products discussed below.
How It Works
Semaglutide activates the GLP-1 receptor, found on pancreatic beta cells and in central appetite-regulating pathways in the brain. Receptor activation increases glucose-dependent insulin secretion, suppresses inappropriately elevated glucagon, slows gastric emptying, and reduces appetite and food intake.[4] Because insulin release is glucose-dependent, semaglutide alone carries a lower intrinsic hypoglycemia risk than insulin or sulfonylureas, though that risk rises when it is combined with those drugs.[3]
What the Research Shows
Semaglutide has one of the most extensive human evidence bases of any peptide drug, spanning the STEP program for weight management, the SUSTAIN and PIONEER programs for type 2 diabetes, and dedicated cardiovascular-outcomes trials.[5] In the STEP 1 trial, adults with obesity or overweight lost significantly more body weight on semaglutide 2.4 mg than on placebo over 68 weeks, and the SELECT cardiovascular-outcomes trial reported fewer major adverse cardiovascular events in adults with established cardiovascular disease and overweight or obesity, without diabetes.[6]
SUSTAIN-6 similarly reported reduced cardiovascular events in people with type 2 diabetes at high cardiovascular risk. These are large, randomized, FDA-reviewed trials — a materially stronger evidence base than exists for most other peptides — though results are population- and dose-specific, and stopping treatment has been associated with weight regain in extension studies.[7]
Safety & Side Effects
Gastrointestinal effects — nausea, vomiting, diarrhea, constipation, and abdominal pain — are the most common adverse effects and a frequent reason for discontinuation.[3] Serious risks noted in labeling include pancreatitis, gallbladder disease, and acute kidney injury, along with a boxed warning about thyroid C-cell tumors observed in rodent studies; the drug is contraindicated in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2.[3]
Because semaglutide delays gastric emptying, it can affect absorption of other oral medications, and labeling advises discontinuation before a planned pregnancy given limited human reproductive data.[3]
Regulatory Status
Semaglutide is FDA-approved, but approval is product- and indication-specific: Ozempic and Rybelsus for type 2 diabetes, and Wegovy for chronic weight management and select cardiovascular risk reduction.[3] The European Medicines Agency has separately authorized semaglutide products for defined indications in Europe, though labeling and availability differ by jurisdiction.[9] None of these approvals extend automatically to off-label uses outside their studied populations.
Compounded & Grey-Market Semaglutide
The surge in demand for GLP-1 drugs has fueled a large market in compounded and online "research" semaglutide, often sold in vials for self-injection outside any prescription relationship. The FDA has specifically warned about dosing errors associated with compounded injectable semaglutide, and has noted that some products use salt forms — semaglutide sodium or semaglutide acetate — that are chemically different from the semaglutide used in Ozempic, Wegovy, and Rybelsus.[8]
A product being marketed as "semaglutide" does not mean it has been manufactured, dosed, or tested to the same standard as the approved drug. Compounded medicines are not reviewed by the FDA for safety, effectiveness, or quality before they reach the market, and buyers have no independent assurance of what is actually in the vial.