Semaglutide Side Effects: The Muscle-Loss Question, the Nausea, and What's Actually Serious

What are the most common semaglutide side effects?

Semaglutide slows digestion and turns down hunger signals in the brain. Almost every common side effect traces back to that. The best count of how often each one happens is Wegovy's FDA label, which pools its main weight-loss trials. In those trials, 73% of people on semaglutide had some stomach or bowel side effect, against 47% on placebo. Placebo here means a look-alike shot with no drug in it.

Severe stomach side effects were much rarer. They affected 4.1% of people on the drug, against 0.9% on placebo. Here is how the main side effects compare.

• Nausea: 44% on semaglutide, against 16% on placebo. It is the top complaint and peaks after each dose increase.
• Diarrhea: 30%, against 16% on placebo.
• Vomiting: about 1 in 4 people, against 6% on placebo. It is more likely early in treatment.
• Constipation: 24%, against 11% on placebo.
• Stomach pain: 20%, against 10% on placebo. Bloating, burping, gas and heartburn are also more common on the drug.
• Headache and tiredness: headache 14% against 10%, tiredness 11% against 5%. Dizziness is also a little more common.
• Changes in skin sensation: tingling, burning or sensitive skin, in 2% against 1% on placebo. This one rises sharply at the stronger 7.2 mg dose.
• Injection-site reactions: uncommon, at about 1 in 100 people, close to the placebo rate.

None of this means something has gone wrong. These effects come with how the drug works. That is why the dose starts low and climbs slowly. In the trials, about 7 in 100 people on semaglutide stopped it because of side effects, against about 3 in 100 on placebo.

How to relieve nausea from semaglutide

Wegovy's label says stomach side effects show up most during the dose increases. A few habits cover most of what happens in those weeks.

• Keep the climb slow. Each dose step is spaced out so your gut can adjust. If a step is hard to tolerate, the label lets your prescriber delay the next increase by 4 weeks. That is a fair thing to ask for.
• Eat smaller, lower-fat meals. Semaglutide already slows how fast your stomach empties. A large or fatty meal on top of that is a common nausea trigger.
• Drink enough fluids. Vomiting and diarrhea dry you out. The label warns that dehydration can lead to kidney problems.
• Notice when nausea peaks in your week. You can move your shot day if it helps. The label allows it as long as your last dose was at least 2 days before.

How long do semaglutide side effects last?

Stomach side effects tend to flare after each dose increase, then ease as your body adjusts. In the STEP 1 trial, nausea and diarrhea were usually mild to moderate. They were mostly short-lived and faded with time. So the hardest stretch is usually the climb to your maintenance dose, the steady dose you stay on.

Hair shedding runs on a slower clock. It usually starts a few months into steady weight loss. It usually settles once your weight levels off.

Which side effects need same-day medical attention?

The everyday stomach upset above is one thing. The symptoms below are different, because they can signal one of the serious risks. In Wegovy's trials, gallstones affected 1.6% of people on the drug, against 0.7% on placebo. The label says the gap held even after accounting for how much weight people lost. Pancreatitis, an inflamed pancreas, was rare but confirmed more often on the drug.

This list follows the Wegovy Medication Guide, the FDA-approved leaflet for patients.

• Possible pancreatitis: severe stomach pain that will not go away, with or without vomiting. The pain can spread to your back. The guide says to stop the drug and call right away.
• Possible gallbladder problems: pain in your upper stomach, fever, yellow skin or eyes, or clay-colored stools.
• Dehydration: nausea, vomiting or diarrhea that does not go away. Losing that much fluid can harm your kidneys.
• Serious allergic reaction: swelling of your face, lips, tongue or throat, severe rash or itching, a very fast heartbeat, trouble breathing or swallowing, or fainting. Get medical help right away.
• Possible thyroid tumor: a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath.
• A racing heart at rest: a pounding or racing heartbeat that lasts several minutes.
• Low blood sugar, if you have type 2 diabetes: shakiness, sweating, dizziness, confusion or a fast heartbeat. The risk is higher if you also take insulin or a sulfonylurea, a type of diabetes pill.
• Vision changes, if you have type 2 diabetes.

Any one of these is worth a same-day call to your prescriber or urgent care, not a message that waits until morning.

Does semaglutide cause muscle loss, especially in perimenopause?

Yes, some. When you lose weight fast, part of what goes is lean tissue, meaning muscle and other non-fat tissue. STEP 1, semaglutide's main weight-loss trial, scanned a group of people to split fat from lean mass. About 6 in 10 pounds lost were fat. Most of the rest was lean tissue.

Timing is what changes the stakes. In your 40s and 50s, muscle is already harder to keep, and the menopause years add to that. So lean tissue lost on the drug comes out of a smaller reserve. That is why women over 40 ask this question so often. For the research, how semaglutide and tirzepatide compare, and what protects your muscle, see GLP-1s and muscle loss in perimenopause.

Does semaglutide cause hair loss?

It can, mostly as a side effect of losing weight. Wegovy's label says hair loss in its trials was linked to weight reduction. Among women, it was reported in 4% on the drug, against 2% on placebo. At the stronger 7.2 mg dose, it reached 8.4% of women, against 1.5% on placebo.

The usual pattern is telogen effluvium, a temporary shedding that fast weight loss can trigger. It tends to start a few months after the weight loss begins, not right after the first shot. It usually settles as your weight stabilizes. If you also notice perimenopausal thinning, perimenopause hair loss explains how it differs from pattern hair loss and what helps.

Do the semaglutide pill and the stronger shot have different side effects?

Semaglutide also comes as a daily pill. Wegovy's label says the common side effects of the 25 mg Wegovy pill were similar in type and frequency to the shot. A few stand out in the pill trial. Severe stomach side effects affected 2% on the pill, against none on placebo. Gallstones affected 2.5%, against 1% on placebo.

The Ozempic pill is a daily tablet for type 2 diabetes, in 1.5, 4 and 9 mg strengths. It shares one FDA label with Rybelsus, but the two are not interchangeable milligram for milligram. Its side-effect data come from Rybelsus trials in type 2 diabetes. At the top 14 mg Rybelsus dose, nausea affected 20% of people, against 6% on placebo.

The weekly shot now also comes in a stronger 7.2 mg dose, sold as Wegovy HD. Most side effects look much like the usual 2.4 mg dose. The big change is in skin sensations, such as tingling, burning or sensitive skin. They affected 22% of people at 7.2 mg, against 6% at 2.4 mg.

Is semaglutide safe?

For most people, yes. Semaglutide has been FDA-approved since 2017, first for type 2 diabetes. Its weight-loss dose has its own large trials. One of them, SELECT, found fewer major heart events in adults with heart disease and overweight or obesity. That is a combined count of heart attacks, strokes and heart deaths. The FDA now approves Wegovy for that use.

Ozempic and Wegovy share the same active ingredient but carry different approvals. Ozempic is approved for type 2 diabetes, including lowering heart and kidney risks in people with diabetes. It is not approved for weight loss, so using it that way is off-label. Ozempic tops out at 2 mg a week, while Wegovy's usual dose is 2.4 mg. Insurance coverage for one use does not carry over to the other.

Two points from the label matter in your 40s. If you might want to get pregnant, stop semaglutide at least 2 months before trying, because it stays in the body a long time. Before any surgery or sedation, tell the team you take it. The drug slows your stomach, and leftover food can get into the lungs under anesthesia.

You may have heard about a link to suicidal thoughts. In January 2026, the FDA said its review found no increased risk of suicidal thoughts or behavior with GLP-1 drugs, the family semaglutide belongs to. It asked the makers of Wegovy, Saxenda and Zepbound to remove that warning. Wegovy's label dropped it in February 2026. Ozempic's label never carried it.

Does semaglutide cause cancer?

Semaglutide carries a boxed warning, the FDA's strongest label warning, about thyroid C-cell tumors. In mice and rats, it caused these tumors at exposures similar to those in people. The label says it is unknown whether it does the same in humans. Cases of medullary thyroid cancer have been reported in people taking liraglutide, an older drug in the same family. Those reports can neither prove nor rule out a link.

Medullary thyroid cancer is a rare type, different from the common thyroid cancers. You should not take semaglutide if you or a family member has had it. The same goes if you have MEN 2, an inherited condition that causes tumors in hormone glands.

For other cancers, the best recent evidence is reassuring. A 2026 review in the Annals of Internal Medicine pooled 48 placebo-controlled trials with about 94,000 people. It found GLP-1 drugs probably have little or no effect on the risk of pancreatic, thyroid, breast or kidney cancer. Results held when the authors looked at semaglutide and tirzepatide trials. Those trials ran a few years at most, so this is not a lifetime answer.

What are the long-term side effects of semaglutide?

Semaglutide's longest record comes from people with type 2 diabetes. Weight-loss use is newer, often at higher doses and for longer. Bones are one thing to watch after menopause. In the SELECT heart trial, women on Wegovy had more hip and pelvis fractures than women on placebo: 1% against 0.2%.

Stopping is the other big question. In the STEP 1 extension, people stopped semaglutide and the trial's lifestyle program, then were followed for a year. They regained about two-thirds of the weight they had lost. Most of their gains in blood pressure, blood sugar and cholesterol slid back toward the start. The authors concluded that ongoing treatment is needed to keep the benefits.

Researchers are still learning how many years of weight loss on the drug affect bone and muscle. Real-world use is now far larger than the trials, so that picture will keep filling in.

Compounded vs. brand semaglutide: does the source change your side-effect risk?

Many online programs sell compounded semaglutide. A licensed pharmacy mixes it, instead of Novo Nordisk making it as Wegovy or Ozempic. The active ingredient can be the same. But the FDA does not review compounded versions for safety, effectiveness and quality before they are sold. Quality depends on the pharmacy that fills your order.

Dosing is the clearest added risk. The FDA has received reports of side effects, some needing a hospital stay, linked to dosing errors with compounded semaglutide shots. Patients measured the wrong amount from a vial, and sometimes clinicians miscalculated the dose. A prefilled brand pen with set doses avoids that kind of mistake.

As of May 2026, the FDA had 990 reports of side effects tied to compounded semaglutide. Many look like the side effects of the approved drug. The FDA says the real number is likely higher, because regular compounding pharmacies do not have to report them.

Compounding is still allowed in some cases, when a licensed pharmacy makes the drug for one named patient with a prescription. In April 2026, the FDA proposed not to add semaglutide to the 503B bulks list. That list would let large outsourcing pharmacies make it from bulk powder. No final decision had been published as of October 2026.

Before you sign up anywhere, ask which pharmacy fills your prescription. Ask for its certificate of analysis, a lab report on the batch. A legitimate program will answer plainly.

If you take Ozempic, Ozempic side effects covers the same ground for that product. Wegovy side effects goes deeper on the weight-loss brand. The broader GLP-1 side-effect guide helps if you are weighing semaglutide against tirzepatide.

Choosing where to start, with side effects in mind

If side effects are part of your decision, three things differ between programs. Some charge more as your dose rises, so a slower climb to ease nausea also keeps your bill lower. Some let you switch between a shot and a tablet without changing provider. Some include a dietitian, which helps when appetite changes are the hard part. Our reviews of Mochi Health, Henry Meds, Fridays and Willow cover each one, with current prices. Brand-name Wegovy is made to one FDA-approved standard, so it does not vary from pharmacy to pharmacy.