Semaglutide
Ozempic · Wegovy · Rybelsus · NN9535 · semaglutida · semaglutid
Coming soon
What Semaglutide is
Semaglutide is a modified version of GLP-1, a 31-amino-acid hormone made in the gut. Novo Nordisk designed it by changing two amino acids and attaching a fatty-acid chain to one lysine. These changes protect the molecule from a common breakdown enzyme and help it bind to albumin in the blood, so it lasts much longer in the body than natural GLP-1. It is sold under the brand names Ozempic, Wegovy and Rybelsus. Many products sold as research-grade or compounded semaglutide also exist, and they are made outside that approved supply chain.
Semaglutide is one of the most heavily studied peptide drugs. Most of the large clinical trials were funded by its manufacturer, and they tested the approved products, not research-grade or compounded material. FDA has approved semaglutide as a prescription drug. It has also warned that compounded versions are not FDA-approved, that semaglutide salt forms are different active ingredients, and that counterfeit and "research use" products may contain the wrong amount of drug or the wrong ingredient. Published test purchases have found vials with the wrong amount of semaglutide, low purity and endotoxin. Labels on these products cannot be trusted at face value, and lots can differ, so each lot needs to be tested for identity, content, purity and contamination.
| Sequence | His-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu-Gly-Gln-Ala-Ala-Lys(side chain)-Glu-Phe-Ile-Ala-Trp-Leu-Val-Arg-Gly-Arg-Gly-OH |
|---|---|
| One-letter code | HXEGTFTSDVSSYLEGQAAKEFIAWLVRGRG |
| Length | 31 amino acids |
| Molecular formula | C187H291N45O59 |
| Molecular weight | ≈4113.58 Da |
| Expected m/z | [set when the lab validates the method] |
Modifications and look-alikes
Modifications
Analogue of human GLP-1(7-37) with two amino-acid substitutions and one acylation (GLP-1 numbering). Position 8 (residue 2 of the chain, X in the one-letter code) is Aib (alpha-aminoisobutyric acid), which protects against DPP-4 cleavage. Position 34 (residue 28) is Arg instead of the native Lys, so only one lysine is left for acylation. Lys26 (residue 20) carries, on its side-chain amine, a hydrophilic spacer joined to a C18 fatty diacid (octadecanedioic acid); this drives albumin binding. The spacer is commonly described as two 8-amino-3,6-dioxaoctanoic acid (OEG/AEEA) units plus one gamma-glutamic acid; that composition reproduces the C187H291N45O59 formula but was not read from a cited source in this draft. C-terminus is a free acid (Gly-OH), not an amide. Monoisotopic mass 4111.1154 Da (KEGG D10025). The approved drug's peptide backbone is produced by yeast fermentation (FDA-approved Ozempic label); research-grade material is typically made by other routes, which is one source of differing impurity profiles.
What it gets confused with
(1) Salt forms. FDA states that semaglutide sodium and semaglutide acetate are different active ingredients from the semaglutide base in approved drugs. The counterion does not change the peptide ion an LC-MS method detects, but it does change how much powder corresponds to a given amount of semaglutide, so content results must state whether they are expressed as semaglutide base. (2) Brand names. Ozempic, Wegovy and Rybelsus are Novo Nordisk brand names for products containing semaglutide; they are not separate molecules. Kyinsu is a combination product of insulin icodec and semaglutide (KEGG D13245). (3) Other GLP-1 agents. Liraglutide is a related acylated GLP-1 analogue with a different sequence and side chain, and tirzepatide and retatrutide are different molecules altogether. A vial labelled "semaglutide" or "GLP-1" could contain one of these; identity testing by expected mass tells them apart. (4) Oral versus injectable products. Tablet products contain the absorption enhancer SNAC as well as semaglutide, so the sample matrix differs from a lyophilised vial.
Identity sources: pubchem.ncbi.nlm.nih.gov · kegg.jp · dailymed.nlm.nih.gov · doi.org · fda.gov
Regulatory status. FDA-approved prescription drug marketed by Novo Nordisk (brands include Ozempic and Wegovy). Compounded semaglutide is not FDA-approved, and FDA does not review it for safety, effectiveness or quality. FDA states that semaglutide sodium and semaglutide acetate are different active ingredients from the one in approved drugs, and that it knows of no lawful basis for using them in compounding. FDA has warned about counterfeit semaglutide and about products falsely labelled 'for research purposes' or 'not for human consumption'. On 21 February 2025, FDA declared the semaglutide injection shortage resolved, which ended the temporary shortage-based allowances for compounding near-copies. Vialidate tests research-grade and compounded material for product quality only; a test result does not mean a product is approved, safe or suitable for use.
Read the research summary and referencesSemaglutide test results
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Vialidate Labs reports analytical results only. Nothing on this page is medical advice or a recommendation to use any compound.