# Semaglutide: What the Diabetes, Weight & Heart Trials Measured > Semaglutide is a GLP-1 receptor agonist with a deep clinical record — glycemic control first, then weight, heart and kidney outcomes. Plain-English, cited summaries. A calm, cited reading of the published record, glycemic control first: what SUSTAIN, STEP, SELECT and FLOW actually measured, with every number pinned to its study. ## The short version Semaglutide is a once-weekly (or once-daily, in tablet form) medicine for type 2 diabetes and weight management. It copies a natural gut hormone called GLP-1 (a signal your body releases after a meal that tells the pancreas to make insulin and tells the brain you are full). Because it lasts about a week in the body, one dose keeps working for days. In diabetes, it lowers blood sugar and trims weight. In a large weight-loss trial it cut body weight by about 15% on average. It also lowered the risk of heart attacks and strokes in people with heart disease, and slowed kidney decline in people with diabetes and kidney disease. The trade-off is mostly the stomach: nausea, and changes in bowel habits, worst early on. What people report — including the downsides — is laid out plainly on [the effects page](/effects). Nothing here is medical advice or a dose to follow. ## What is semaglutide Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist — a man-made copy of the gut hormone GLP-1 that has been re-engineered to last far longer in the body [1][14]. Native GLP-1 is destroyed within about two minutes by an enzyme called DPP-4 (dipeptidyl peptidase-4, a protein-cutting enzyme in the blood). Semaglutide swaps one building block at position 8 for a non-standard amino acid (Aib) that DPP-4 cannot cut, and attaches a long fatty-acid chain that clings reversibly to albumin (the most abundant carrier protein in blood). That albumin grip shields the molecule from the kidneys and stretches its half-life to roughly one week [14]. The practical result is a medicine you can dose once a week by injection, or once a day as a tablet, rather than several times a day. It is approved across several conditions: type 2 diabetes, chronic weight management, reducing major heart events in people with established cardiovascular disease and excess weight, and, as of 2025, a form of fatty liver disease called MASH [3][13]. The pages here read each of those approvals back through the trials that earned them, starting with the glycemic (blood-sugar) evidence. ## The glycemic and cardiovascular record, first In type 2 diabetes, the headline finding is a reliable drop in HbA1c — the blood marker that reflects average glucose over about three months. Across the SUSTAIN program, once-weekly semaglutide lowered HbA1c and body weight versus placebo and versus comparator drugs, with the 2.0 mg dose lowering HbA1c more than 1.0 mg [8][11][12]. The cardiovascular evidence is what moved semaglutide from a glucose drug to a cardiometabolic one. In SUSTAIN-6, once-weekly semaglutide (0.5 or 1.0 mg) cut the combined rate of cardiovascular death, nonfatal heart attack and nonfatal stroke by 26% (hazard ratio 0.74; 95% CI 0.58-0.95) in people with type 2 diabetes at high cardiovascular risk [2]. The same trial flagged a real caution: among people who already had diabetic eye disease and whose blood sugar fell quickly, retinopathy complications were more frequent (HR 1.76) [2]. The full picture, including the safety signals, is in the [Semaglutide research](/research). ## Weight, kidney and the once-weekly peptide The same molecule that steadies blood sugar also drives substantial weight loss. In STEP 1, once-weekly subcutaneous semaglutide 2.4 mg produced a mean body-weight change of -14.9% from baseline to week 68, versus -2.4% with placebo, in adults with overweight or obesity who did not have diabetes [1]. In SELECT (n=17,604), the same 2.4 mg dose cut major adverse cardiovascular events by 20% (HR 0.80) in people with established heart disease and excess weight but no diabetes [3]. The kidney is the newest chapter. In FLOW (n=3,533), once-weekly semaglutide 1.0 mg lowered the risk of major kidney-disease events — kidney failure, a large fall in filtration, or kidney or cardiovascular death — by 24% (HR 0.76) in type 2 diabetes with chronic kidney disease [6]. As a semaglutide peptide, this is a 31-amino-acid acylated analogue of human GLP-1 — a small protein, not a small-molecule pill in the classic sense, which is why the injectable form is dosed weekly and the oral form needs a special absorption helper. How it produces all of this, from the pancreas to the appetite centers of the brain, is covered in [how does semaglutide work](/how-it-works) and in [semaglutide mechanism of action](/mechanism-of-action). --- A calm, glycemic-first reading of the semaglutide record — the SUSTAIN, STEP, SELECT and FLOW figures logged where the trials confirm them, the boxed thyroid warning and the still-unconfirmed cancer signals kept in plain sight, and the community reports pinned to one side as anecdote; no clinic behind the name, no prescription written, and nothing here dosed, compounded, or sold.