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What is semaglutide?

Semaglutide explained in plain English: what it is, what the research shows, side effects, legal status and dosage, plus a calculator for syringe units. Doses shown come only from the label or published trials, each with its source. Also called Ozempic, Wegovy, Rybelsus, Sema.

Semaglutide is a prescription medicine. This page is educational; use it only as prescribed by a qualified healthcare professional.

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Syringe, no result yetU-100, 1 mL syringe holding up to 100 units. Enter your dose.0102030405060708090100

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What is semaglutide?

Semaglutide is a prescription medicine made by Novo Nordisk that copies GLP-1, a hormone the gut releases after eating. It is the active ingredient in Ozempic, Wegovy and Rybelsus.

It is a peptide: a chain of 31 amino acids, modified so it lasts about a week in the body. That’s why the injections are taken once a week.

What is semaglutide used for?

Semaglutide is FDA-approved to lower blood sugar in type 2 diabetes (Ozempic and Rybelsus) and for long-term weight management (Wegovy). Wegovy is also approved to lower the risk of heart attack and stroke in people with heart disease and excess weight.

Other approvals followed: Ozempic for kidney disease in people with type 2 diabetes, and Wegovy for a fatty liver disease called MASH. In December 2025 the FDA approved a Wegovy pill for weight loss, the first GLP-1 pill for that use.

How does semaglutide work?

Semaglutide switches on GLP-1 receptors. It helps the pancreas release insulin when blood sugar is high, slows how fast the stomach empties and acts on the brain to reduce hunger.

People on it usually feel full sooner and think about food less, which is what drives the weight loss.

What do the semaglutide trials show?

In STEP 1, adults with obesity lost an average of 14.9% of their body weight over 68 weeks on weekly Wegovy-strength semaglutide, compared with 2.4% on placebo. About 86% lost at least 5% of their weight.

In the SELECT trial, semaglutide lowered the risk of heart attack, stroke or heart-related death by about 20% in people with heart disease and overweight. Weight tends to come back after stopping, so it is treated as a long-term medicine.

Semaglutide side effects

The most common side effects are nausea, vomiting, diarrhea, constipation and stomach pain, especially when the dose is being raised. They usually ease over time.

Less common but serious risks include pancreatitis, gallbladder problems, kidney injury from dehydration, and low blood sugar when combined with insulin or some other diabetes medicines. It carries a boxed warning because it caused thyroid tumors in rodents, so it isn’t used by people with a personal or family history of medullary thyroid cancer or MEN 2.

Mostly not anymore. Pharmacies were allowed to make copies while semaglutide was on the FDA shortage list, but the shortage ended in February 2025.

In April 2026 the FDA also proposed removing semaglutide from the list of ingredients large compounding facilities can use. Products sold online as “research” semaglutide are not approved for human use, and the FDA has warned about wrong strengths and contamination in unapproved versions.

How much does semaglutide cost?

In the US, list prices for Ozempic and Wegovy are over a thousand dollars a month before insurance, though Novo Nordisk offers lower cash-pay prices and coverage varies widely. There is no US generic yet; the main patent runs to 2031, while Canada approved generics in 2026.

How do you reconstitute semaglutide?

Ozempic and Wegovy come ready to use in pens, so they’re never mixed. If you have a powder vial, the calculator above turns the vial size, the bacteriostatic water and a dose into syringe units, and the reconstitution guide explains each step.

See the dosage section below for what is known about doses, with sources.

Semaglutide dosage

Semaglutide always starts at a low dose that rises every 4 weeks to limit stomach side effects. Wegovy (weight) and Ozempic (type 2 diabetes) follow different schedules, and the Wegovy tablet has its own daily schedule.

From the official prescribing information (label). Your prescriber decides your dose and when to change it.

Semaglutide doses, with sources
WhenDoseHow often
Wegovy injection, weeks 1–40.25 mg[1]Once a week
Wegovy injection, weeks 5–80.5 mg[1]Once a week
Wegovy injection, weeks 9–121 mg[1]Once a week
Wegovy injection, weeks 13–161.7 mg[1]Once a week
Wegovy injection, maintenance (week 17 on)2.4 mg (or 1.7 mg)[1]Once a week
Ozempic, weeks 1–4 (start only)0.25 mg[2]Once a week
Ozempic, from week 50.5 mg[2]Once a week
Ozempic, if needed after 4+ weeks1 mg, then up to 2 mg (maximum)[2]Once a week
Wegovy tablets, days 1–30, 31–60, 61–901.5 mg, then 4 mg, then 9 mg[3]Once a day
Wegovy tablets, maintenance (day 91 on)25 mg[3]Once a day
  1. Novo Nordisk, Wegovy prescribing information
  2. Novo Nordisk, Ozempic prescribing information
  3. Drugs.com, Wegovy dosage guide (injection and tablets, from the label)

Medical disclaimer: this dosage information is for education only and comes from the source shown for each row. It is not medical advice and not a recommendation for you. Only a licensed prescriber who knows your health can decide whether Semaglutide is right for you and at what dose. Don't start, change or stop a medicine based on this page, and don't use research peptides or unapproved drugs based on trial doses.

Semaglutide concentration chart

The concentration of a Semaglutide vial depends only on its size and the water you add. Each unit on a U-100 syringe holds one hundredth of a mL.

Semaglutide concentration by vial size and water
Vial + waterConcentrationPer unit (U-100)
5 mg + 1 mL5,000 mcg/mL (5 mg/mL)50 mcg per unit (0.05 mg per unit)
5 mg + 2 mL2,500 mcg/mL (2.5 mg/mL)25 mcg per unit (0.025 mg per unit)
5 mg + 3 mL1,666.67 mcg/mL (1.66667 mg/mL)16.67 mcg per unit (0.01667 mg per unit)
10 mg + 1 mL10,000 mcg/mL (10 mg/mL)100 mcg per unit (0.1 mg per unit)
10 mg + 2 mL5,000 mcg/mL (5 mg/mL)50 mcg per unit (0.05 mg per unit)
10 mg + 3 mL3,333.33 mcg/mL (3.33333 mg/mL)33.33 mcg per unit (0.03333 mg per unit)

Frequently asked questions

Is semaglutide the same as Ozempic?

Semaglutide is the medicine inside Ozempic. Wegovy and Rybelsus also contain semaglutide; they differ in what they're approved for and how they're taken.

How much weight do people lose on semaglutide?

In the STEP 1 trial, adults with obesity lost an average of 14.9% of their body weight over 68 weeks, compared with 2.4% on placebo. Individual results vary widely.

What happens when you stop semaglutide?

Most people regain much of the weight. In a follow-up of STEP 1, people regained about two-thirds of the weight they had lost within a year of stopping.

Is compounded semaglutide legal?

Copies were allowed during the shortage, which ended in February 2025. In April 2026 the FDA proposed removing semaglutide from the list that large compounders can use, which would end most remaining compounding.

Is there a generic semaglutide?

Not in the US, where the main patent runs to 2031. Canada approved its first generic semaglutide in April 2026 after a Canadian patent lapsed.

Sources

  1. Wilding et al. (2021), Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1), New England Journal of Medicine
  2. AJMC (2025), FDA Approves Oral Semaglutide as First GLP-1 Pill for Weight Loss
  3. Medscape (2026), FDA Proposes End to Mass GLP-1 Compounding
  4. Drug Discovery Trends (2026), Canada approves generic semaglutide

Last updated .

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