Weight is the reason almost everyone starts. It is not the strongest evidence these drugs have. Semaglutide is one of a small number of obesity treatments with a completed cardiovascular outcome trial. That trial is why a clinician may reach for this molecule in particular, rather than whichever one a seller happens to be discounting on the price boards.
SELECT, the trial the claim rests on
SELECT enrolled 17,604 patients aged 45 or older who had preexisting cardiovascular disease and a body-mass index of 27 or greater, and no history of diabetes. They were assigned 1:1 to once-weekly semaglutide 2.4 mg or placebo. The primary endpoint was a composite of death from cardiovascular causes, nonfatal myocardial infarction or nonfatal stroke.[1]
Over a mean follow-up of 39.8 months, a primary endpoint event occurred in 569 of 8,803 patients on semaglutide (6.5%) against 701 of 8,801 on placebo (8.0%), a hazard ratio of 0.80 (95% CI, 0.72 to 0.90).[1]
What a 20% relative reduction is in people
The relative figure is the one every landing page quotes. The absolute difference is 1.5 percentage points over roughly three and a quarter years. On those rates, about 67 patients were treated for that period for each primary event avoided. That is a genuinely valuable result in people who had already had a cardiovascular event. It is also a much smaller promise than “cuts heart attacks by a fifth” sounds, and both figures belong on the same page.
Discontinuation tells the other half of the story. Adverse events led to permanent discontinuation of the trial product in 16.6% on semaglutide against 8.2% on placebo.[1] Roughly one participant in six stopped, which is the practical context for the side-effect article and for any plan sold on an annual prepayment.
Who SELECT was actually about
Every participant already had established cardiovascular disease. This is a secondary-prevention trial, and its result describes risk reduction in people who have already had a heart attack, a stroke or symptomatic peripheral arterial disease. It does not establish that a 38-year-old with a BMI of 31 and no cardiac history gains the same protection.
The entry criteria are worth reading literally. Participants had to be 45 or older, carry a body-mass index of 27 or greater, and have documented cardiovascular disease, while anyone with a history of diabetes was excluded.[1] That is a narrow slice of the people who buy these drugs online, and the trial's own authors describe the result as applying to patients with preexisting cardiovascular disease and overweight or obesity but without diabetes.
That distinction survives into the buying decision. A reader whose reason for treatment is cardiovascular risk has a strong argument for this molecule at this dose. A reader whose reason is a wedding in June is making a different decision, and one whose real cost turns on how long treatment continues — the subject of the stopping article.
The diabetes trials came first
SUSTAIN-6 randomized 3,297 patients with type 2 diabetes to semaglutide 0.5 mg or 1.0 mg or placebo for 104 weeks. The primary composite occurred in 6.6% against 8.9%, a hazard ratio of 0.74 (95% CI, 0.58 to 0.95), driven largely by a reduction in nonfatal stroke.[2]
That trial also carries a finding no honest summary omits: rates of retinopathy complications were significantly higher on semaglutide, with a hazard ratio of 1.76 (95% CI, 1.11 to 2.78).[2]Anyone with existing diabetic eye disease needs that discussed before starting, not after.
The class result is older still. LEADER randomized 9,340 patients with type 2 diabetes and high cardiovascular risk to liraglutide or placebo over a median 3.8 years. The primary composite occurred in 13.0% against 14.9%, a hazard ratio of 0.87 (95% CI, 0.78 to 0.97), and death from cardiovascular causes in 4.7% against 6.0%.[3]
Heart failure and kidneys
STEP-HFpEF randomized 529 patients with heart failure with preserved ejection fraction and obesity. Symptom scores improved by 16.6 points against 8.7 on placebo, six-minute walk distance by 21.5 m against 1.2 m, and C-reactive protein fell 43.5% against 7.3%.[4]Serious adverse events were reported in 13.3% of the semaglutide group against 26.7% on placebo.
FLOW then randomized 3,533 patients with type 2 diabetes and chronic kidney disease to semaglutide 1.0 mg or placebo and was stopped early. Major kidney disease events were 24% less likely on semaglutide (hazard ratio, 0.76; 95% CI, 0.66 to 0.88), with major cardiovascular events 18% lower and death from any cause 20% lower.[5]
Read together, those trials describe a drug doing something beyond appetite in several organ systems. They were also run in populations selected for disease, which is the recurring caveat on this page. How a figure gets established here before it is published is set out in the methodology.
What this evidence does not cover
No cardiovascular outcome trial has reported for tirzepatide in this population, which is the clearest asymmetry in the class and points the opposite way from the weight figures in the molecule comparison. If cardiovascular risk is the reason for treatment, semaglutide is the molecule with the outcome data behind it.
Every trial here also studied branded, FDA-approved product at labeled doses under supervision. Compounded preparations, which is what most sellers on the review index actually dispense, have never been through that review. A hazard ratio earned by a branded product in a 17,604-patient trial is not a property that transfers to a vial by sharing a molecule name.