Is Semaglutide Safe to Take for Years? What the Long-Term Trial Data Actually Shows

The Question Nobody Asked Five Years Ago

When semaglutide first hit pharmacy shelves, everyone wanted to know one thing: does it work? Now, millions of prescriptions later, the question has shifted. People aren't wondering if they'll lose weight anymore. They're wondering what happens to their bodies after taking this medication for five, ten, maybe fifteen years.

It's a fair concern. We've been burned before. Remember fen-phen? That weight loss combination seemed miraculous until heart valve damage started showing up years later. So when your doctor suggests staying on semaglutide indefinitely, you deserve more than reassurance. You deserve data.

Good news: we finally have some. The SELECT trial, published in the New England Journal of Medicine in 2023, followed 17,604 adults for a mean of 39.8 months, and other large trials—FLOW for kidneys and the STEP program for weight maintenance and mental health—fill in more of the picture. Together they give us a real, if still incomplete, window into longer-term semaglutide use.

What the SELECT Trial Actually Found After 5 Years

The SELECT trial wasn't designed to study weight loss. It enrolled adults aged 45 or older with established cardiovascular disease and a BMI of 27 or higher, but without diabetes—the kind of patients whose doctors lose sleep worrying about heart attacks. Half got semaglutide 2.4 mg weekly. Half got placebo. Then researchers watched and waited.

After a mean follow-up of 39.8 months, the results were striking. Major adverse cardiovascular events—cardiovascular death, nonfatal heart attack, and nonfatal stroke—occurred in 6.5% of the semaglutide group versus 8.0% on placebo, a 20% relative reduction (hazard ratio 0.80). That's not a small number for people already receiving standard heart care.

But here's what matters for the safety conversation: the trial also tracked every side effect, every hospitalization, every concerning lab value. And the picture that emerged was more nuanced than either enthusiasts or skeptics expected.

Tolerability was the main trade-off. Adverse events led to permanent discontinuation in 16.6% of the semaglutide group versus 8.2% on placebo. Gastrointestinal effects such as nausea, vomiting and diarrhea are the most common side effects of semaglutide and occur mostly during dose escalation.

The Muscle Mass Question Gets Real Answers

If you've spent any time in weight loss communities, you've heard the worry: "Sure, you lose fat, but you're also losing muscle." This concern isn't unfounded. According to a 2024 review in Diabetes, Obesity and Metabolism, the share of weight lost as lean mass in GLP-1 trials has varied widely—from about 15% or less in some studies to 40-60% in others.

The same review adds nuance: lean mass is not the same as muscle (it also includes organs, bone and water), and MRI-based studies suggest muscle changes on GLP-1 therapy are largely proportional to the weight lost, with improved muscle quality. The authors still flag older age and severe disease as reasons for caution because of sarcopenia risk. Adequate protein and resistance training remain the commonly recommended countermeasures, though long-term trial data on them are limited.

Thyroid Concerns: Separating Signal from Noise

Every semaglutide package carries a black box warning about thyroid C-cell tumors. This warning exists because rodent studies showed increased thyroid cancer risk. But rodent thyroid biology differs substantially from human thyroid biology. So what do five years of human data tell us?

Human data so far are reassuring but not definitive. A Scandinavian cohort study in the BMJ (2024), following 145,410 GLP-1 users for a mean of 3.9 years, found no increased risk of thyroid cancer compared with DPP-4 inhibitor users (hazard ratio 0.93, 95% CI 0.66-1.31). A French case-control study in Diabetes Care (2023), however, linked 1-3 years of GLP-1 use to a higher risk (hazard ratio 1.58), so the question isn't fully closed.

For people with personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2, the calculus is different. These conditions remain absolute contraindications. But for the general population, five years of surveillance hasn't revealed the thyroid cancer signal that some feared.

Gallbladder Disease: The Underappreciated Risk

Here's something that doesn't get enough attention: gallbladder problems. Rapid weight loss has always increased gallstone risk—this isn't unique to GLP-1 medications. But a 2022 meta-analysis of 76 randomized trials (103,371 patients) in JAMA Internal Medicine found that GLP-1 receptor agonists raised the risk of gallbladder or biliary disease (relative risk 1.37). In Wegovy's U.S. label, gallstones were reported in 1.6% of treated adults versus 0.7% on placebo.

The risk was higher in weight-loss trials, at higher doses, and with longer use. The Wegovy label also notes that acute gallbladder disease was more common with the drug even after accounting for the degree of weight loss. Part of the mechanism is familiar: when you lose fat rapidly, your liver secretes more cholesterol into bile, which can crystallize into stones.

Ursodeoxycholic acid is sometimes used to prevent gallstones after bariatric surgery, but it isn't a standard recommendation for people on GLP-1 medications. At minimum, knowing the symptoms of gallbladder disease—right upper abdominal pain, especially after fatty meals, fever, or yellowing of the skin or eyes—seems prudent for anyone on long-term therapy, and those symptoms warrant prompt medical care.

Kidney Function Over Time

The kidney story is actually encouraging. GLP-1 receptor agonists appear to have protective effects on kidney function, separate from their weight loss benefits. The FLOW trial (completed in 2024) specifically examined kidney outcomes in people with type 2 diabetes and chronic kidney disease.

After a median follow-up of 3.4 years, semaglutide lowered the risk of major kidney disease events—kidney failure, a sustained drop of 50% or more in kidney function, or death from kidney or cardiovascular causes—by 24%. The yearly decline in kidney function was slower, and death from any cause was 20% lower.

For people without kidney disease, the main kidney caution is short-term: the label warns that dehydration from vomiting or diarrhea can lead to acute kidney injury, so staying hydrated during GI side effects matters. Periodic kidney function tests remain reasonable, but the trial data so far don't suggest that long-term GLP-1 exposure harms the kidneys.

Mental Health: The Complicated Picture

In 2023, European regulators investigated reports of suicidal thoughts among GLP-1 users. In April 2024, the EMA's safety committee concluded that the available evidence does not support a causal link. Trial data provide further context.

A post hoc analysis of the STEP 1, 2, 3 and 5 trials (JAMA Internal Medicine, 2024) found that semaglutide 2.4 mg did not increase depressive symptoms or suicidal ideation or behavior compared with placebo; 1% or fewer of participants reported suicidal ideation or behavior, with no difference between groups. In January 2026, the suicidal behavior and ideation warning was removed from the U.S. Wegovy label.

However, those trials excluded people with known major psychiatric disorders. So we can't extrapolate these findings to everyone. What we can say: in people without pre-existing major mental illness, semaglutide didn't increase psychiatric adverse events.

Anecdotally, some users report feeling "flat" or experiencing reduced food-related pleasure. This isn't captured well in clinical trial endpoints. It's worth discussing with your healthcare provider if you notice mood changes, even subtle ones.

What Happens When You Stop?

The STEP trials paint a consistent picture: most people regain weight after stopping semaglutide. In the STEP 1 extension, participants who had lost 17.3% of their body weight over 68 weeks regained about two-thirds of it within a year of stopping. In STEP 4, people switched to placebo after 20 weeks regained 6.9% of their body weight, while those who stayed on semaglutide lost a further 7.9%.

This isn't a failure of the medication. It reflects biology. Obesity involves persistent changes in hunger hormones, metabolic rate, and brain reward circuitry. When you remove the medication that was helping regulate these systems, the underlying drivers of weight gain remain.

Some researchers now frame GLP-1 medications like blood pressure medications or statins—tools for managing chronic conditions rather than short-term fixes. Whether that framing is appropriate remains debated, but it does align with what the data shows about weight regain after discontinuation.

Making Sense of Five Years of Evidence

So, is semaglutide safe to take for years? The honest answer is: safer than we had any right to expect, with caveats.

The cardiovascular benefits are real and substantial. A 20% reduction in heart attacks and strokes isn't trivial—for high-risk patients, this rivals the benefit of medications we've used for decades. Kidney protection appears genuine. The thyroid cancer fears, while not completely dismissed, haven't materialized into clear human risk.

The trade-offs are also real. Gastrointestinal side effects bother some people indefinitely. Muscle loss requires active countermeasures. Gallbladder disease risk increases, especially with rapid weight loss. And we still don't know what fifteen or twenty years of use looks like.

That's about as confident as medical science gets. Five years of data from thousands of participants tells us a lot. It doesn't tell us everything. For now, the evidence suggests that for most people, the benefits of long-term semaglutide use outweigh the known risks—especially when combined with lifestyle measures that protect muscle mass and when monitored appropriately for emerging concerns.