# Semaglutide Research: The Trial Record by Outcome > Semaglutide research summarized by outcome — kidney, cardiovascular, weight, glycemic, and head-to-head trials, each finding cited to its source. Kidney, cardiovascular, weight, and glycemic evidence from the registrational program, plus the head-to-head and mechanism data — every finding attributed. ## The short version This page walks through what the semaglutide studies actually measured, organized by outcome rather than by trial name. The headline numbers: weight fell about 15% over 68 weeks in the main obesity trial [1]; heart attacks and strokes dropped 20% in people with heart disease and obesity [3]; major kidney events dropped 24% in people with diabetes and kidney disease [6]. We lead with the kidney evidence because that is this site's focus, then cover the heart, weight, and blood-sugar findings, how the drug works in the brain, and how it compares with tirzepatide. Each claim links to a study on the references page. Numbers are reported as the trials measured them, in the third person — never as advice. ## Renal outcomes: the FLOW trial The strongest kidney evidence is FLOW, a trial of 3,533 adults with type 2 diabetes and chronic kidney disease. Once-weekly semaglutide 1.0 mg reduced the primary kidney composite — kidney failure, a sustained 50% or greater fall in estimated glomerular filtration rate (eGFR, a measure of how well the kidneys filter), or death from kidney or cardiovascular causes — by 24% versus placebo (HR 0.76; 95% CI 0.66-0.88) [6]. A pre-specified analysis examined whether the benefit depended on how advanced the kidney disease was at baseline; the cardiovascular benefit was consistent across severity strata [12]. FLOW read out in 2024 and is the basis for framing semaglutide as a kidney-protective agent in this population. The mechanism is thought to combine blood-pressure, weight, and glycemic effects with direct actions at renal GLP-1 receptors, though the trial measured outcomes rather than mechanism. ## Cardiovascular outcomes Three trials anchor the cardiovascular record. In SUSTAIN-6, once-weekly semaglutide (0.5 or 1.0 mg) reduced the composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke in type 2 diabetes at high risk (HR 0.74; 95% CI 0.58-0.95) — though rates of diabetic-retinopathy complications were higher in that trial (HR 1.76; 95% CI 1.11-2.78) [2]. In SELECT, 17,604 adults with established cardiovascular disease and overweight or obesity but no diabetes had a 20% lower rate of major adverse cardiovascular events on semaglutide 2.4 mg versus placebo (HR 0.80; 95% CI 0.72-0.90; P<0.001) [3]. SELECT was pivotal because it extended cardiovascular benefit to people without diabetes. In STEP-HFpEF, semaglutide 2.4 mg improved heart-failure symptoms and physical limitation and produced greater weight loss in obesity-related heart failure with preserved ejection fraction [11]. ## Semaglutide weight loss The weight-loss evidence is large and reproducible. 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 without diabetes — a treatment difference of about 12.4 percentage points [1]. The effect is durable while treatment continues: a two-year trial reported sustained, clinically meaningful weight loss versus placebo [10]. Semaglutide also improved multiple cardiometabolic risk factors — waist circumference, blood pressure, lipids, glycemia, and inflammatory markers — in exploratory analyses [21]. The weight-lowering effect is central rather than metabolic: it reduces food intake without lowering energy expenditure (see the mechanism section). ## Glycemic control in type 2 diabetes Semaglutide's first approved use was glucose control. Across the subcutaneous (SUSTAIN) and oral (PIONEER) programs, it produced dose-dependent reductions in HbA1c (glycated hemoglobin, a marker of average blood sugar over about three months) and body weight. In a head-to-head against another weekly GLP-1 agonist, once-weekly semaglutide produced greater reductions in HbA1c and body weight than dulaglutide [7]. A meta-analysis of once-daily oral semaglutide reported efficacy in glycemic control and weight, with a cardiovascular profile consistent with the GLP-1 receptor agonist class [4]. These are glucose-lowering and weight findings; the cardiovascular and kidney benefits above came from dedicated outcome trials. ## How it works: the CNS mechanism The weight effect is driven by the brain. In rodent studies, semaglutide lowered body weight by acting through distributed central nervous system pathways: it directly reached the brainstem, area postrema (a brain region without a full blood-brain barrier), hypothalamic arcuate nucleus, and parabrachial nucleus, reducing food intake and shifting food preference without decreasing energy expenditure [22]. Mechanistically, semaglutide activates satiety-promoting POMC/CART neurons and inhibits hunger-driving NPY/AgRP neurons in the arcuate nucleus, while the area postrema and parabrachial nucleus signal meal termination. The same brainstem access that mediates appetite suppression is also implicated in nausea — the benefit and the most common side effect share an anatomy. For the plain-English version, see [how does semaglutide work](/how-it-works). ## Semaglutide vs tirzepatide The most direct comparison is SURMOUNT-5, a head-to-head trial of 751 adults with obesity. Tirzepatide — a dual GIP/GLP-1 receptor agonist — produced greater mean weight loss than semaglutide at 72 weeks (-20.2% vs -13.7%; difference statistically significant, P<0.001) [23]. The pattern held in diabetes: in an earlier head-to-head, tirzepatide produced greater HbA1c and weight reductions than once-weekly semaglutide 1.0 mg [24]. The two molecules differ by design — tirzepatide engages a second incretin receptor (GIP) in addition to GLP-1 — which is the leading explanation for the larger average effect. Semaglutide retains the more mature cardiovascular and kidney outcome record. ## Compounded semaglutide A note the "legal" framing of this site warrants: not all semaglutide is the approved manufactured product. During the federally declared shortage of roughly 2022 to early 2025, compounding pharmacies were permitted to prepare semaglutide; that pathway was curtailed once the shortage was declared resolved in 2025 [9]. The approved product carries the trial evidence summarized on this page; compounded or non-pharmaceutical preparations fall outside that approved-product evidence base. This is the published-record distinction between the approved drug and a compounded version, framed editorially — it is not legal advice, and this site does not supply either form. --- 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.