Ozempic (semaglutide) has been studied in clinical trials lasting up to five years, and the overall safety profile is reassuring for most people. The largest and longest trial, called SELECT, followed over 17,000 participants for a median of about 40 months and found a 20% reduction in major cardiovascular events like heart attacks and strokes. That said, long-term use does come with specific risks worth understanding, particularly around muscle loss, bone health, and what happens if you stop.
What the Longest Trials Tell Us
Most medications are tested over weeks or months before approval. Semaglutide has more long-term data than many drugs in its class. The SELECT trial ran for up to five years, tracking cardiovascular outcomes in people with obesity who did not have diabetes. The result was not just neutral safety but an active benefit: participants on semaglutide had 20% fewer heart attacks, strokes, and cardiovascular deaths compared to those on placebo.
For people with type 2 diabetes, the SUSTAIN series of trials provided additional data over one to two years. These trials established that blood sugar control remained stable over time without new safety signals emerging as treatment continued. The picture from clinical trials, taken together, is that semaglutide doesn’t appear to become more dangerous the longer you take it.
Muscle Loss Is a Real Concern
When you lose weight on Ozempic, not all of it comes from fat. In the STEP-1 trial, participants lost an average of 15.3 kg (about 34 pounds), but roughly 7 kg of that was lean mass, meaning muscle and other non-fat tissue. That works out to about 45% of total weight loss coming from lean mass, which is significantly higher than the general expectation that about one-quarter of weight loss should come from lean tissue.
This matters because losing muscle affects your metabolism, physical strength, and balance, especially as you age. The concern isn’t theoretical. People who lose large amounts of muscle are more prone to falls, fatigue, and a slower metabolic rate that can make weight maintenance harder down the road. Resistance training and adequate protein intake are the most effective ways to counteract this, and many clinicians now recommend both as standard practice alongside the medication.
Bone Health in Older Adults
The relationship between semaglutide and bone density is still being sorted out, but early signals deserve attention. A 52-week trial that produced significant weight loss (around 8.8% more than placebo) found measurably lower bone density at the hip and lumbar spine in the semaglutide group. Markers of bone breakdown were also elevated.
More concerning, data from a longer trial with over 40 months of follow-up found nearly a five-fold higher incidence of hip and pelvic fractures in adults aged 75 and older who were taking semaglutide compared to placebo. A shorter 20-week pilot trial in older adults with prediabetes or type 2 diabetes found no significant bone density changes, but the treatment period was likely too brief and the weight loss too modest to trigger the effect. The pattern suggests that bone risk scales with the amount of weight lost and the age of the person taking it. If you’re over 65 and on semaglutide long term, bone density monitoring is worth discussing with your doctor.
Thyroid Cancer: What the Warning Means
Ozempic carries an FDA black box warning about medullary thyroid carcinoma (MTC), a rare form that accounts for roughly 3% of all thyroid cancer diagnoses. This warning exists because early animal studies showed that rodents given semaglutide developed thyroid C-cell tumors at higher rates.
However, recent research has challenged whether this risk translates to humans. Rodent thyroid cells respond to this class of drug differently than human cells do, and population-level studies in people taking semaglutide have not confirmed an increased rate of MTC. The black box warning remains in place as a precaution, and the medication is not recommended for anyone with a personal or family history of MTC or a rare condition called Multiple Endocrine Neoplasia syndrome type 2.
Pancreatitis Risk Appears Low
Early concerns about GLP-1 drugs and pancreas inflammation have largely been addressed by accumulating data. A meta-analysis of semaglutide trials specifically found no increased risk of acute pancreatitis compared to placebo, with an odds ratio of 0.7 regardless of dose, formulation, or whether the drug was being used for diabetes or weight loss. A broader analysis pooling data from over 102,000 participants across multiple GLP-1 drugs reached the same conclusion: the relationship between these medications and pancreatitis is statistically neutral.
That said, symptoms of pancreatitis (severe abdominal pain that radiates to your back, especially after eating) should always be taken seriously. People with a history of pancreatitis may face a different risk profile than what clinical trial averages reflect.
Eye Health for People With Diabetes
If you have type 2 diabetes and already have some degree of diabetic retinopathy, this is one area where Ozempic carries a specific caution. In the two-year SUSTAIN-6 trial, retinopathy complications (including bleeding in the eye and conditions requiring laser treatment) occurred in 3.0% of participants on semaglutide compared to 1.8% on placebo. The risk was concentrated among people who already had retinopathy at the start: 8.2% experienced complications on semaglutide versus 5.2% on placebo.
The leading theory is that rapid drops in blood sugar can temporarily worsen retinopathy, similar to what has been seen with insulin therapy. Later real-world studies comparing GLP-1 drugs to other diabetes medications have not found a significant difference in retinopathy worsening, but the initial trial data prompted an official label warning. If you have existing diabetic eye disease, regular eye exams during treatment are important.
What Happens When You Stop
One of the most practical long-term considerations isn’t a side effect of taking Ozempic. It’s what happens when you stop. A systematic review and meta-analysis published in The Lancet found that within one year of stopping a GLP-1 drug, people regained about 60% of the weight they had lost during treatment. The researchers estimated that weight regain eventually plateaus at around 75% of the original weight lost.
This means that if you lost 30 pounds on Ozempic, you could expect to regain roughly 18 pounds within a year of stopping, with the total creeping toward 22 to 23 pounds over time. This isn’t a failure of willpower. The medication suppresses appetite and changes how your body regulates hunger hormones, and when it’s removed, those signals return. For many people, this means semaglutide is an ongoing treatment rather than a temporary intervention, which makes the long-term safety profile all the more relevant.
Ongoing Monitoring While on Treatment
If you’re taking Ozempic for type 2 diabetes, your doctor will typically check your A1C (a measure of average blood sugar over three months) at least twice a year, along with periodic kidney function tests through blood or urine samples. Home blood sugar monitoring is also standard. For people with a history of diabetic retinopathy, regular eye exams should continue throughout treatment.
For those using semaglutide primarily for weight management, monitoring tends to focus on nutritional status, muscle mass preservation, and metabolic markers. There are no special lab tests unique to semaglutide, but staying aware of symptoms like persistent nausea, unusual abdominal pain, or vision changes helps catch uncommon complications early.