What Is Semaglutide?

Semaglutide is a GLP-1 receptor agonist. GLP-1 is a hormone your gut releases after you eat. It tells your pancreas to release insulin, tells your liver to stop dumping glucose into your bloodstream, slows how quickly food leaves your stomach, and signals your brain that you're full.

Natural GLP-1 breaks down within minutes. Semaglutide is a modified version engineered to survive in the body for about a week — which is why the injectable form is taken once weekly rather than several times a day.

The result: better blood sugar control, reduced appetite, and — for most people who take it at weight-management doses — meaningful weight loss.

Semaglutide acts on GLP-1 receptors in several places at once:

In the pancreas.It increases insulin release when blood glucose is elevated and suppresses glucagon, the hormone that raises blood sugar. Because this effect is glucose-dependent, semaglutide alone carries a low risk of hypoglycemia — though that risk rises when it's combined with insulin or sulfonylureas.

In the stomach. It slows gastric emptying, so food sits longer and you feel full sooner and for longer after a meal. This is also the source of most of its side effects.

In the brain.Receptors in the hypothalamus and brainstem regulate hunger and satiety. Many patients describe the effect as a reduction in “food noise” — the persistent background chatter about what and when to eat next.

In blood vessels and other tissues. GLP-1 receptors appear throughout the cardiovascular system, which is part of why semaglutide has demonstrated benefits beyond glucose and weight.

All of these contain the same active ingredient. The differences are dose, delivery, and approved indication.

A few notes on the differences:

• Ozempic and Wegovy are the same drug at different ceilings. Ozempic maxes out at 2 mg weekly for diabetes; Wegovy goes to 2.4 mg for weight management. Insurance coverage and labeling, more than pharmacology, drive which one a patient ends up on.
• Oral semaglutide is a newer arrival. The first oral GLP-1 approved for chronic weight management reached the US market in early 2026. Rybelsus, the original oral semaglutide for type 2 diabetes, has been superseded in the US by a reformulated tablet under the Ozempic name.
• The oral and injectable forms are not milligram-for-milligram interchangeable. Switching between them is a clinical decision, not a substitution.

Weight. In the STEP 1 trial, adults with obesity taking semaglutide 2.4 mg weekly lost an average of about 15% of body weight over 68 weeks, versus roughly 2.5% on placebo. Individual results varied widely — some participants lost far more, some far less.

Cardiovascular events. The SELECT trial studied adults with established cardiovascular disease and overweight or obesity, but without diabetes. Semaglutide reduced major adverse cardiovascular events — cardiovascular death, heart attack, stroke — by roughly 20% compared to placebo. This was the finding that repositioned GLP-1s from weight-loss drugs to cardiometabolic drugs.

Blood sugar. Across the SUSTAIN program, semaglutide produced HbA1c reductions that generally exceeded other injectable diabetes medications it was tested against.

Kidney and liver. Semaglutide has since been approved for slowing kidney disease progression in patients with type 2 diabetes and chronic kidney disease, and — under accelerated approval — for metabolic dysfunction-associated steatohepatitis (MASH) with liver fibrosis.

Oral formulation. In the OASIS 4 trial, adults taking oral semaglutide 25 mg daily lost an average of about 16.6% of body weight at 64 weeks among those who stayed fully adherent, versus about 2.7% on placebo.

Semaglutide is started at a low dose and increased gradually over several months. This isn't arbitrary — the escalation schedule exists to let the gastrointestinal system adapt. Starting at a full therapeutic dose would make most people miserable.

The injectable form is a subcutaneous injection into the abdomen, thigh, or upper arm, taken once a week on the same day each week. The needle is short and fine; most patients describe it as considerably less unpleasant than they expected.

The oral form is taken once daily. Absorption of oral semaglutide is sensitive to food and fluid, so the specific tablet's instructions on fasting windows matter.

Common.Nausea, vomiting, diarrhea, constipation, abdominal pain, and burping. These are most pronounced during dose escalation and typically ease over time. Eating smaller portions, stopping before you're full, and avoiding high-fat meals helps considerably.

Less common but serious. Pancreatitis, gallbladder disease including gallstones, kidney injury from dehydration secondary to vomiting, and worsening of diabetic retinopathy in some patients with diabetes.

Boxed warning. Semaglutide carries an FDA boxed warning for thyroid C-cell tumors, based on findings in rodents. Whether this translates to humans is unknown, but the drug is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.

Pregnancy. Semaglutide is contraindicated in pregnancy and is not recommended while breastfeeding. Because it can improve fertility in some patients, contraception planning is a real and frequently overlooked conversation.

Anesthesia.Because semaglutide delays gastric emptying, tell your surgical or anesthesia team you're taking it well before any procedure requiring sedation.

This is not a complete list. Full prescribing information for any specific product should be reviewed with a licensed clinician.

Semaglutide treats obesity as a chronic condition, not as a finite course of therapy. In the STEP 4 withdrawal study, participants who discontinued regained a substantial share of the weight they'd lost within a year, and cardiometabolic improvements largely reverted alongside it.

This isn't a failure of the drug or the patient — it's how the underlying biology works. Appetite regulation returns to its prior set point when the medication is withdrawn. It's worth understanding this before starting, because it shapes what a realistic long-term plan looks like.

During the 2022–2025 shortages of Ozempic and Wegovy, US compounding pharmacies were permitted to prepare semaglutide under specific regulatory exemptions. The FDA declared the shortage resolved in early 2025, and the conditions permitting large-scale compounding of copies changed accordingly.

Two things are worth knowing regardless of what you're offered:

1. Compounded medications are not FDA-approved.They aren't reviewed for safety, efficacy, or manufacturing quality the way branded products are. That's true of all compounded drugs, not just semaglutide.
2. “Semaglutide” isn't always semaglutide. Products marketed as semaglutide salts — sodium or acetate forms — are different substances from the active ingredient in approved products, and the FDA has specifically flagged them.

If you're evaluating any semaglutide product, ask which pharmacy is dispensing it, whether it's a 503A or 503B facility, whether it's registered and in good standing with its state board, and whether third-party potency and sterility testing is available.