Definition / Renal-outcomes lens
What Is Semaglutide? The GLP-1 Peptide Explained
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 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 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.
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.