What is Semaglutide?

Semaglutide (Novo Nordisk development code NN9535) is a long-acting synthetic peptide developed as a research tool for probing signalling through the glucagon-like peptide-1 (GLP-1) receptor. It is described in the academic literature as a selective, high-affinity GLP-1 receptor agonist and has become the canonical single-receptor reference compound for laboratory groups studying incretin biology, insulin secretion and body-weight regulation.

BuyRetaUK supplies semaglutide as a sterile lyophilised powder at ≥99% HPLC purity, with a batch-specific Certificate of Analysis, packed for research handling in temperature-controlled UK storage. It is strictly for in-vitro laboratory use and is not approved by BuyRetaUK for human or veterinary administration.

Semaglutide is the active peptide behind clinically branded medicines such as Ozempic and Wegovy; the research-grade material supplied here is the underlying peptide entity, not a branded medicinal product.

Semaglutide was disclosed by Novo Nordisk as NN9535 and characterised across a body of peer-reviewed pharmacology work from 2012 onward. The peptide was engineered from the native GLP-1 backbone with two amino-acid substitutions and a C18 fatty diacid moiety, extending plasma half-life via reversible albumin binding to enable weekly dosing regimens in the studies that reference it.

The compound is supported by the Novo Nordisk SUSTAIN clinical trial programme (type-2 diabetes research) and the STEP programme (body-weight research). For laboratory buyers, semaglutide's status as the archetypal single GLP-1 receptor agonist makes it the standard comparator when characterising newer dual and triple agonist molecules such as tirzepatide and retatrutide.

NN9535 is the Novo Nordisk internal development code for semaglutide. The two names refer to the same 31-amino-acid synthetic peptide bearing a C18 fatty diacid side chain, which extends plasma half-life through non-covalent albumin binding in the studies that report its pharmacokinetics. Laboratory suppliers frequently list the compound under both names, and analytical certificates typically reference NN9535 in the identity block alongside the semaglutide INN.

When cross-referencing publications, NN9535 is the term most likely to appear in preclinical and mechanism-of-action papers, while semaglutide is more common in clinical and metabolic literature.

A GLP-1 receptor agonist is a molecule — peptide or small molecule — that activates the GLP-1 receptor to mimic the action of the endogenous incretin hormone GLP-1. Semaglutide sits within this class as a peptide agonist; alongside it are earlier compounds such as exenatide, liraglutide and dulaglutide, all engineered to resist degradation by dipeptidyl peptidase-4 (DPP-4).

In receptor pharmacology assays semaglutide is characterised as a potent, near-full agonist of the GLP-1 receptor with a residence time and half-life optimised for extended exposure. This receptor profile is the primary mechanistic feature that distinguishes semaglutide from dual agonists (tirzepatide, GLP-1 + GIP) and triple agonists (retatrutide, GLP-1 + GIP + glucagon) currently in wide research use.

Endogenous GLP-1 is a 30-amino-acid peptide released from intestinal L-cells in response to nutrient intake. Once secreted it is degraded within one to two minutes by DPP-4 and neutral endopeptidases — a half-life too short for extended experimental readouts. Semaglutide was designed to overcome this: a substitution at position 8 (aminoisobutyric acid) resists DPP-4 cleavage, while a spacer-linked C18 fatty diacid promotes reversible binding to serum albumin.

The net effect in the literature is a plasma half-life of approximately one week rather than minutes, enabling stable receptor occupancy across long experimental windows without the sub-minute clearance characteristic of native GLP-1. Aside from these pharmacokinetic modifications the peptide retains high sequence homology with native GLP-1 across the receptor-binding regions.

Published research references semaglutide across metabolic, glycaemic and body-composition models — investigating the effect of sustained GLP-1 receptor activation on insulin secretion, food intake, gastric emptying and energy balance. Because it acts as a selective single-receptor agonist, semaglutide is a natural benchmark in studies that partition the receptor-level contribution of the GLP-1 axis to overall incretin response.

A full research-workflow summary lives at /retatrutide-research and applies equally to semaglutide-based experimental designs.

The SUSTAIN clinical trial programme evaluated semaglutide across a series of Phase 3 studies in type-2 diabetes research. The STEP programme extended the evidence base into body-weight and obesity research. Both programmes are frequently referenced by laboratory groups needing an established human pharmacology background against which to frame in-vitro semaglutide work.

For a comparative view of related trial programmes — SURPASS and SURMOUNT for tirzepatide, TRIUMPH for retatrutide — see the /glp-1-research-hub overview.

Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist that adds GIP receptor activity; retatrutide is a triple agonist that further adds glucagon receptor activity. For laboratories building comparative datasets, semaglutide typically appears as the single-agonist reference alongside tirzepatide (dual) and retatrutide (triple).

Our dedicated comparison guide at /retatrutide-vs-semaglutide covers the full side-by-side receptor and class analysis.

Lyophilised semaglutide vials are stored at 2–8°C protected from light. For long-term storage below -20°C is acceptable; repeated freeze-thaw of the lyophilised powder is not recommended. Once reconstituted with bacteriostatic water the peptide is stored refrigerated (2–8°C) and used within approximately 30 days.

Volume-per-dose calculations for laboratory dilution are handled by our /reconstitution-calculator. A future /semaglutide-storage guide will expand this into a full cold-chain protocol.

BuyRetaUK semaglutide is released at ≥99% HPLC purity with mass spectrometry identity confirmation. The purity value on the batch-specific COA is derived from reverse-phase HPLC with UV detection, expressed as the percentage of total peak area. Identity is confirmed against the theoretical monoisotopic mass of semaglutide.

A future /semaglutide-purity guide will provide the detailed analytical protocol.

Every BuyRetaUK batch is produced to research-grade specifications, quarantined until analytical release, then dispatched from temperature-controlled UK storage with a batch-specific Certificate of Analysis. Full batch traceability — sequence identity, purity, appearance and cold-chain history — is maintained for every lot.

For a full account of our quality workflow see the Laboratory Quality Standards guide at /laboratory-quality.

Vials are lyophilised under sterile conditions, sealed under inert gas and quarantined at 2–8°C pending analytical sign-off. Shipping is temperature-controlled and every order arrives with the batch-specific COA that matches the lot printed on the vial.

Each semaglutide lot ships with a batch-specific Certificate of Analysis covering identity (mass spectrometry), purity (reverse-phase HPLC with UV detection at ≥99%), appearance and endotoxin (LAL assay). The lot number on the COA matches the lot printed on the vial, so any batch can be independently cross-referenced.

For the full anatomy of a peptide COA — how the HPLC, mass spectrometry and endotoxin sections are structured — see /knowledge-hub/certificate-of-analysis-guide.