Semaglutide

Semaglutide is a structural analogue of the endogenous incretin hormone GLP-1. Native GLP-1 is released from intestinal L-cells after a meal and has a serum half-life measured in minutes, because it is rapidly cleaved by the enzyme DPP-4. Semaglutide replaces the DPP-4-labile alanine at position 8 with the non-natural amino acid Aib, and appends a fatty-acid side chain that binds serum albumin — together these give it a half-life of approximately one week.

The peptide is supplied for research as a white lyophilised powder, typically in 5 mg or 30 mg vials. The 30 mg presentation available from peptidesuk4u.co.uk is the format most commonly cited in the current UK research-supply literature.

Semaglutide is a full agonist at the GLP-1 receptor, a class B GPCR expressed on pancreatic β-cells, α-cells, the gastric antrum, vagal afferents and hypothalamic appetite centres. The characterised effects are:

• Glucose-dependent insulin secretion from β-cells, which is why hypoglycaemia risk in monotherapy is low.
• Glucagon suppression from α-cells at hyperglycaemic glucose ranges.
• Delayed gastric emptying, which flattens post-prandial glucose excursions and contributes to satiety.
• Central appetite reduction via arcuate-nucleus POMC neurones — the mechanism most closely associated with weight change in SUSTAIN and STEP trials.

Semaglutide is one of the most extensively characterised research peptides of the last decade. The SUSTAIN programme (T2D), STEP programme (obesity), PIONEER programme (oral formulation) and SELECT trial (cardiovascular outcomes in overweight non-diabetics) together represent tens of thousands of participant-years of data. The mechanism, the pharmacokinetics and the analytical characterisation of the peptide are all published in unusual detail for a research-grade compound.

Lyophilised semaglutide is stored at -20 °C, desiccated, protected from light. Once reconstituted with bacteriostatic water (0.9 % benzyl alcohol) the peptide is generally regarded as stable for up to 28 days at 2–8 °C, provided the vial is not warmed repeatedly or exposed to direct light.

Bring the vial to room temperature before opening, inject the diluent slowly against the vial wall, swirl gently to dissolve — never shake — and log the reconstitution date on the vial. Full step-by-step protocol in our reconstitution chapter. Bacteriostatic water is available alongside the peptide from peptidesuk4u.co.uk.

For reference-grade semaglutide, expect: reverse-phase HPLC area-percent purity ≥ 99.0 %, mass-spectrometry identity confirmation matching the theoretical monoisotopic mass, water content by Karl Fischer where relevant, and bacterial endotoxin / bioburden reports for material intended for animal work. Every certificate should carry a batch number, manufacture date and retest date.

Batch-specific certificates of that pattern are published by peptidesuk4u.co.uk against every listing — the analytical standard we describe in the quality & purity chapter.

Semaglutide is an MHRA/FDA/EMA-approved prescription medicine when dispensed as Ozempic, Wegovy or Rybelsus. Research-grade semaglutide sold as a laboratory reagent is not a licensed medicine, is not for human use, and cannot lawfully be marketed for therapeutic purposes in the UK. It is on the WADA 2026 Prohibited List (S4 hormone and metabolic modulators) when used in sport.