Clinical trials

SELECT Trial Explained: Semaglutide and Heart Health

The SELECT trial followed 17,604 people with heart disease and excess weight for about four years and found semaglutide cut major cardiac events by 20% — here is what that number means and what it does not.

Last verified September 14, 2026·13 sources cited·Wegovy

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Before SELECT, semaglutide was a drug that lowered blood sugar and reduced body weight. After SELECT, it became a drug that prevents heart attacks and strokes. That shift is the single biggest reason semaglutide moved from a lifestyle conversation into a cardiology conversation, and it is why insurers who would not pay for weight loss started paying for something else.

This page explains what SELECT tested, what the results were, how to read the numbers honestly, and what the trial did not settle.

What was the SELECT trial?

SELECT stands for Semaglutide Effects on Cardiovascular Outcomes in People with Overweight or Obesity. It was registered as NCT03574597, sponsored by Novo Nordisk, and ran from October 2018 to June 2023 [1].

The design was a multicenter, double-blind, randomized, placebo-controlled, event-driven superiority trial. That is a mouthful, so here is what each part means:

Double-blind: neither participants nor investigators knew who was getting the drug.
Placebo-controlled: the comparison group received matching injections containing no active drug, on top of whatever standard care they were already receiving — statins, blood pressure drugs, aspirin and so on.
Event-driven: the trial did not stop on a fixed date. It ran until enough cardiac events had accumulated to answer the question.
Superiority: the goal was to show semaglutide was better than placebo, not merely safe.

Who was enrolled matters just as much. Participants had to be 45 or older, have a body mass index of 27 or higher, have established cardiovascular disease — a prior heart attack, prior stroke, or symptomatic peripheral artery disease — and not have diabetes [2]. That exclusion was deliberate. Earlier trials such as SUSTAIN 6 had already shown a cardiovascular benefit in people with type 2 diabetes [3]. The open question was whether the benefit held in people whose main risk factor was excess weight.

A total of 17,604 people were randomized, 8,803 to semaglutide 2.4 mg once weekly and 8,801 to placebo. Mean exposure was 34.2 months and mean follow-up was 39.8 months [2].

What did SELECT find?

The primary endpoint was the first occurrence of any one of three things: death from cardiovascular causes, a nonfatal heart attack, or a nonfatal stroke. Cardiologists call this composite “three-point MACE,” short for major adverse cardiovascular events.

A primary endpoint event occurred in 569 of 8,803 people on semaglutide (6.5%) and 701 of 8,801 people on placebo (8.0%). The hazard ratio was 0.80, with a 95% confidence interval of 0.72 to 0.90 and a p-value below 0.001 [2].

That is the headline: a 20% relative reduction in major cardiac events.

Each individual component of the composite pointed in the same direction. Only the difference in nonfatal heart attacks reached statistical significance on its own, which is normal — composite endpoints exist precisely because individual components are usually too rare to test separately [4].

How should you interpret “20% lower risk”?

This is where a lot of coverage goes wrong, so it is worth slowing down.

A 20% relative reduction sounds enormous. The absolute reduction was 1.5 percentage points — from 8.0% down to 6.5% over roughly three and a half years. Both numbers describe exactly the same result. They just answer different questions.

Another way to express it: roughly 67 people with this risk profile would need to take semaglutide for about 40 months to prevent one major cardiac event. That is a respectable number for a preventive therapy. For comparison, it sits in the same general territory as many widely used cardiovascular medications. But it also means most people who take the drug for this purpose will not personally avoid an event they would otherwise have had — which is true of essentially every preventive treatment in medicine.

Whether that trade-off makes sense for any individual depends on their baseline risk, their tolerance for side effects, and cost. Those are questions for a healthcare provider who knows the full picture.

Did the heart benefit come from the weight loss?

Not entirely, and this is one of the most interesting open questions in the field.

Participants on semaglutide lost weight steadily for about 65 weeks and then held roughly flat. At 208 weeks, mean weight reduction was 10.2% versus 1.5% on placebo, waist circumference was down 7.7 cm versus 1.3 cm, and waist-to-height ratio was down 6.9% versus 1.0% [5]. Blood pressure, HbA1c, cholesterol and C-reactive protein all improved [4].

But the event curves in SELECT separated early — within the first few months — before most of the weight loss had accumulated. And the benefit appeared across every baseline BMI category, including people who started closer to a BMI of 27 than 40 [5]. Several analyses have also found the benefit was largely independent of how much HbA1c changed.

Taken together, that pattern suggests semaglutide is doing something to blood vessels and inflammation directly, not only through the scale. The exact mechanism is not settled.

What happened to people’s weight over four years?

SELECT is the longest randomized semaglutide dataset in existence, which makes its weight curve unusually valuable.

The prespecified weight analysis published in Nature Medicine in 2024 showed the shape clearly: weight fell continuously for about 65 weeks, then plateaued and stayed there through week 208 [5]. There was no slow creep back up while people remained on treatment. Clinically meaningful weight loss occurred in both sexes and across every race, body size and geographic region studied.

This is the best available answer to “does it keep working?” As long as treatment continues, the weight loss appears to hold for at least four years. What happens at year six or year ten is genuinely unknown.

What about side effects and dropouts?

SELECT is also the most useful trial for understanding tolerability at scale, simply because it is so large and ran so long.

Adverse events leading to permanent discontinuation of the trial product occurred in 1,461 people on semaglutide (16.6%) versus 718 on placebo (8.2%), a statistically significant difference driven mainly by gastrointestinal symptoms [2]. Overall study drug discontinuation for any reason reached 26.7% in the semaglutide group and 23.6% on placebo over roughly three years, and by two years about 77% of the semaglutide group were on the full 2.4 mg target dose [4].

There is a counterintuitive finding worth noting. Serious adverse events were less frequent with semaglutide than placebo, across every BMI category [5]. That is not a contradiction — nuisance side effects like nausea drive discontinuation, while serious events like hospitalizations were reduced along with cardiac risk.

Where does SELECT fit among the other outcome trials?

SELECT is one piece of a larger picture that now includes four major outcome trials for semaglutide:

SUSTAIN 6 (2016): 3,297 people with type 2 diabetes; MACE hazard ratio 0.74 [3].
SELECT (2023): 17,604 people with cardiovascular disease and excess weight, no diabetes; hazard ratio 0.80 [2].
FLOW (2024): 3,533 people with type 2 diabetes and chronic kidney disease; major kidney events down 24%, cardiovascular death down 29%, death from any cause down 20% [6].
SOUL (2025): 9,650 people with type 2 diabetes and high cardiovascular risk, using the daily tablet; MACE hazard ratio 0.86 [7].

Four separate trials, four different populations, four different primary endpoints, all pointing the same direction. That consistency is what makes the cardiovascular story credible rather than a single fortunate result.

There is also a heart failure thread. Two trials, STEP-HFpEF and STEP-HFpEF DM, showed semaglutide substantially improved symptoms and walking distance in people with obesity-related heart failure with preserved ejection fraction [8][9]. Neither was designed to count hospitalizations. A post-hoc pooled analysis of 3,743 participants with this type of heart failure across SELECT, FLOW and the two STEP-HFpEF trials found cardiovascular death or worsening heart failure occurred in 5.4% on semaglutide versus 7.5% on placebo, a hazard ratio of 0.69 [10]. That is encouraging but, because it is post-hoc, it is suggestive rather than definitive.

What did SELECT not answer?

Several important things.

It did not test people without heart disease. Everyone in SELECT already had a prior heart attack, stroke or peripheral artery disease. Nothing in this trial tells you whether semaglutide prevents a first cardiac event in someone with obesity and no existing cardiovascular disease. That question has not been answered by any completed trial.

It did not compare semaglutide against another GLP-1 drug. The comparison was against placebo plus standard care. Tirzepatide’s equivalent trial in people with obesity and without diabetes, SURMOUNT-MMO, enrolled 15,374 participants; as of September 2026 it is active but not recruiting, with an estimated primary completion date of October 2027 [12]. Until it reports, semaglutide is the only drug in this class with proven heart-event reduction in this population.

It did not run beyond four years. SELECT-LIFE, an observational follow-on study of 3,439 former SELECT participants, finished data collection in August 2025, but no results had been published as of September 2026 [11]. It is also worth being clear about what a follow-on of this kind can and cannot show: once the trial ended, so did the randomized comparison, so any long-term findings will be observational rather than randomized evidence.

It did not establish a mortality benefit as a primary result. Death from any cause was lower numerically, but it was not the primary endpoint, and headlines claiming semaglutide “saves lives” overstate what SELECT can support on its own.

How did SELECT change what happens in a doctor’s office?

Concretely, in three ways.

First, the FDA approved a new indication for Wegovy in March 2024: reducing the risk of major cardiovascular events in adults with established cardiovascular disease and either obesity or overweight. That is a distinct indication from weight management.

Second, that new indication created a coverage pathway. Medicare Part D is statutorily barred from covering drugs used for weight loss, but not from covering drugs used to reduce cardiovascular risk. SELECT is the reason that distinction exists in practice.

Third, it repositioned the conversation. A cardiologist can now discuss semaglutide as cardiovascular secondary prevention in the same breath as statins and blood pressure control, which is a different conversation from a weight-loss consultation.

None of that means semaglutide is right for any particular person. It has real side effects, real costs, and a substantial discontinuation rate even inside a well-supported clinical trial. Anyone weighing it should talk through their own cardiovascular risk, other medications and tolerance for gastrointestinal symptoms with a healthcare provider.

Sources

Questions people ask

What was the SELECT trial?

SELECT was a randomized, double-blind, placebo-controlled trial of once-weekly semaglutide 2.4 mg in 17,604 adults aged 45 and older who had established cardiovascular disease and a BMI of 27 or higher but did not have diabetes. It ran from 2018 to 2023 and was published in the New England Journal of Medicine in November 2023.

What did the SELECT trial find?

Over an average follow-up of about 40 months, the combined rate of cardiovascular death, nonfatal heart attack and nonfatal stroke was 6.5% in the semaglutide group and 8.0% in the placebo group. That is a hazard ratio of 0.80, usually described as a 20% relative reduction.

What does a 20% reduction actually mean for one person?

In absolute terms, the event rate dropped by about 1.5 percentage points over roughly three and a half years. Put another way, roughly 67 people needed to be treated for about 40 months to prevent one major cardiac event. Whether that trade-off is worthwhile depends on your individual risk, which is a conversation for a healthcare provider.

Did SELECT show semaglutide saves lives?

Death from any cause was numerically lower in the semaglutide group, but all-cause mortality was not the trial's primary endpoint and the result was part of a hierarchical testing sequence. SELECT is best described as reducing major cardiac events rather than as proving a mortality benefit.

Do you need to be diabetic for the SELECT findings to apply?

No — the opposite. SELECT deliberately excluded people with diabetes. Participants had established cardiovascular disease and a BMI of 27 or higher. The earlier SUSTAIN 6 trial covered people with type 2 diabetes.

How much weight did SELECT participants lose?

Mean weight reduction was 10.2% at 208 weeks versus 1.5% on placebo, with waist circumference down 7.7 cm. Weight loss continued for roughly 65 weeks and then held steady for the rest of the four years.

Did SELECT change insurance coverage?

It contributed to it. SELECT supported the FDA's March 2024 approval of a cardiovascular risk-reduction indication for Wegovy, which created a route for Medicare Part D plans to cover semaglutide for that specific purpose rather than for weight loss alone.

How many people stopped taking semaglutide in SELECT?

16.6% of the semaglutide group permanently stopped because of adverse events, compared with 8.2% on placebo. Overall study drug discontinuation reached 26.7% versus 23.6%.

This article summarizes FDA labeling, published research and company information current as of September 14, 2026. It is not medical advice and does not replace a conversation with your own healthcare provider. How we research and verify.