# What Is Semaglutide? The GLP-1 Peptide Explained > What is semaglutide — the GLP-1 receptor agonist peptide, its structure, approved uses, and the kidney and heart evidence, explained plainly and cited. The molecule, the drug class, the approved uses, and the regulatory record — a plain-language primer on the published facts. ## The short version What is semaglutide? It is a prescription medicine that copies a natural gut hormone called GLP-1 to lower appetite and blood sugar. It belongs to a drug class called GLP-1 receptor agonists, and it is approved by the FDA for type 2 diabetes, long-term weight management, lowering heart-attack and stroke risk in certain people, and a fatty-liver disease called MASH. Chemically it is a peptide — a short chain of amino acids, the building blocks of proteins — engineered to last about a week in the body. It comes as a once-weekly injection or a once-daily tablet. In large trials it cut weight, heart events, and kidney decline [1][3][6]. This page lays out what it is, plainly; nothing here is medical advice or for sale. ## Semaglutide peptide: the molecule The semaglutide peptide is a 31-amino-acid acylated analogue of human GLP-1, sharing roughly 94% of its sequence with the natural hormone. "Acylated" means a fatty-acid chain has been attached; that chain binds albumin, a blood protein, which slows clearance and is the structural reason the drug can be dosed once weekly. Two other changes give it staying power: at position 8, the usual amino acid is replaced by alpha-aminoisobutyric acid (Aib) to block the DPP-4 enzyme that destroys native GLP-1, and at position 34 a substitution further stabilizes the molecule. Its molecular formula is C187H291N45O59 and its molecular weight is about 4,114 daltons. These design choices are what separate a fragile two-minute hormone from a once-weekly therapeutic — the same chemistry detailed on the [how does semaglutide work](/how-it-works) page. ## What drug class it belongs to Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist, also called an incretin mimetic. Incretins are gut hormones released after eating that boost insulin and curb appetite; semaglutide imitates one of them. The class includes other agents that activate the same receptor. Semaglutide is distinguished within it by its long half-life, its dual subcutaneous and oral formulations, and an unusually broad outcome record spanning weight, cardiovascular, kidney, and liver endpoints. A related but distinct molecule, tirzepatide, activates a second incretin receptor (GIP) as well — the two are compared head-to-head on the [Semaglutide research](/research) page. ## What it is approved for Semaglutide is an approved prescription medicine, not an experimental compound. The FDA has cleared it across several indications: type 2 diabetes, chronic weight management, reduction of major adverse cardiovascular events in adults with established cardiovascular disease and overweight or obesity, and, in 2025, metabolic dysfunction-associated steatohepatitis (MASH), a serious form of fatty-liver disease [9]. It is available in two formulations — a once-weekly subcutaneous injection and a once-daily oral tablet. The evidence behind these indications comes from large randomized trials: STEP for weight management [1], SUSTAIN-6 and SELECT for cardiovascular outcomes [2][3], FLOW for kidney outcomes [6], and ESSENCE for liver disease [8]. Each is summarized on the research page and listed on the references page. ## What it is used for, and what to watch In practice the molecule is used to lower blood sugar in type 2 diabetes, to support long-term weight management, and — based on the outcome trials — to reduce cardiovascular and kidney risk in the studied populations. People also describe a marked drop in appetite and cravings, summarized as anecdotal reports on [Semaglutide effects](/effects). The trade-off is tolerability. The dominant side effects are gastrointestinal — nausea, vomiting, diarrhea, constipation — mostly mild-to-moderate and worst during dose escalation [5]. There is a boxed warning related to a rare thyroid tumor seen in rodents [16], increased gallbladder disease [5], and substantial weight regain after stopping [13]. The effects page covers these with citations. This primer states what semaglutide is; it does not recommend using it. ## The regulatory record in brief Semaglutide first reached FDA approval for type 2 diabetes in 2017, with the oral tablet following in 2019-2020 and the weight-management indication in 2021 [1]. The cardiovascular indication followed the SELECT readout in 2023 [3], the kidney indication followed FLOW in 2024 [6], and the MASH indication followed in 2025 [8]. The "legal" question many readers arrive with concerns compounded versions. During a federally declared shortage from roughly 2022 to early 2025, compounding pharmacies were permitted to prepare semaglutide; that pathway was curtailed once the shortage was declared resolved [9]. The approved product and a compounded preparation are distinct under the law, and the trial evidence here describes the approved product. This is editorial commentary on the public record, not legal advice. --- A regulatory reading desk on the semaglutide record — the trials, the labeling, and the kidney-outcomes evidence summarized and cited, with no clinic behind the desk, no legal counsel offered, and nothing here prescribed or sold.