Semaglutide

A long-acting glucagon-like peptide-1 (GLP-1) receptor agonist and one of the most heavily studied metabolic research compounds.

What it is

Semaglutide is a synthetic analogue of the human incretin hormone glucagon-like peptide-1 (GLP-1). It shares roughly 94% sequence homology with native GLP-1 (7-37) but carries two engineered modifications that give it a long circulating half-life: an aminoisobutyric acid (Aib) substitution at position 8, which blocks degradation by dipeptidyl peptidase-4 (DPP-4), and a C18 fatty diacid chain attached at lysine-26 through a gamma-glutamate and hydrophilic linker, which drives strong, reversible albumin binding.

Because of that albumin anchoring and DPP-4 resistance, semaglutide has a half-life of about one week, which is what makes the once-weekly dosing schedules used in the trial literature possible. It belongs to the GLP-1 receptor agonist class and is the parent structure behind several widely referenced metabolic research programs. Supplied strictly for laboratory research use only, not for human or veterinary use.

How it works

Semaglutide is a selective agonist at the GLP-1 receptor, a class B G-protein-coupled receptor. Binding activates adenylate cyclase through Gs coupling, raising intracellular cyclic AMP in pancreatic beta cells. This potentiates glucose-dependent insulin secretion, meaning insulin release is amplified only when blood glucose is elevated, while glucagon secretion from alpha cells is suppressed. Because the insulinotropic effect is glucose-dependent, the mechanism carries a low intrinsic hypoglycemia signal in the literature.

Beyond the pancreas, GLP-1 receptors are expressed in the central nervous system, and semaglutide reaches hypothalamic and hindbrain regions that regulate appetite and satiety. Activation of these circuits, together with slowed gastric emptying, reduces energy intake in research models. This central appetite pathway is the leading mechanistic explanation for the large body-weight reductions seen in the clinical literature, distinct from the glycemic pathway acting at the islet.

What the research shows

Semaglutide has been characterised across a large program of randomized controlled trials spanning obesity (the STEP series), type 2 diabetes with cardiovascular risk (SUSTAIN), and cardiovascular disease without diabetes (SELECT). The headline signals are consistent: substantial body-weight reduction in overweight and obese populations, meaningful HbA1c lowering in diabetic populations, and a reduction in major adverse cardiovascular events. The figures below are drawn from the primary trial publications.

Side Effects

Semaglutide's side-effect profile is dominated by gastrointestinal effects, which are common but usually transient and mild to moderate, alongside a small set of serious warnings carried in the FDA prescribing information. The figures below come from the FDA labels on DailyMed for Ozempic (type 2 diabetes) and Wegovy (obesity), plus the pivotal STEP and SUSTAIN trial publications. Reported frequencies differ by product and dose, since Wegovy uses a higher 2.4 mg dose than Ozempic. The serious warnings are far less common than the routine GI complaints but define the drug's contraindications and monitoring.

In short, the routine GI effects such as nausea, vomiting, diarrhea and constipation are frequent but usually mild, dose-related, and fade over time. The serious warnings, including the rodent thyroid C-cell tumor signal, pancreatitis, gallbladder disease, acute kidney injury and diabetic retinopathy complications, are much rarer but are the reasons the label carries contraindications and monitoring guidance.

At a glance

Dosing

Semaglutide is sold under several brand names with different routes and approved uses, and every FDA label starts patients at a low dose and titrates up slowly to limit gastrointestinal effects. Ozempic and Rybelsus are approved for type 2 diabetes (injectable and oral), while Wegovy is approved for chronic weight management and related indications. The doses below are the approved prescribing schedules and the doses studied in the SUSTAIN and STEP trials, not instructions for use.

The slow, stepwise titration exists to reduce nausea and other GI effects while the body adjusts, and the 0.25 mg injectable start and 3 mg oral start are deliberately sub-therapeutic. Effective maintenance doses can sit below the labeled maximum: many diabetes patients are controlled at 0.5 or 1 mg rather than 2 mg. This is educational information on approved and studied doses for laboratory research use only, not medical advice.

Preparing it

Reconstitute the lyophilized powder with bacteriostatic or sterile water, added slowly down the side of the vial and swirled gently, never shaken, until fully dissolved. The volume of water you add sets the concentration of the finished solution, so work this out before drawing anything.

For the full procedure see reconstitution, and to work out concentration per unit see concentration & math.

Compared with related compounds

Semaglutide is a single GLP-1 receptor agonist. Newer research compounds layer on further incretin activity: tirzepatide is a dual GIP / GLP-1 agonist, and retatrutide adds glucagon receptor activity as a triple agonist. Semaglutide remains the most extensively characterised of the group and the usual point of comparison when the newer multi-receptor molecules are studied.

Where to go next

Last updated on July 3, 2026