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Peptide drug (FDA approved)Human trialsFDA approved

Semaglutide

Semaglutide

Last reviewed October 27, 2026 · 26 sources · Written for general readers · Compare with another compound →

The bottom line

Semaglutide is a well studied, FDA approved drug sold as Wegovy, Ozempic and Rybelsus for weight, diabetes, heart, kidney and liver uses. In large trials people lost about 15% of their body weight on average, but most of it came back within a year of stopping. Stomach side effects are common, and copies sold online or as research products are not the approved drug.

Where the evidence stands

What it is

Semaglutide is a lab made version of GLP-1, a gut hormone that helps control appetite and blood sugar. Its chain of building blocks is about 94% the same as the human hormone.[1] It is a prescription drug made by Novo Nordisk and sold in the United States as Wegovy, Ozempic and Rybelsus.[1][2][3]

Wegovy comes as a weekly shot and as a daily pill. Both are approved for weight loss and keeping weight off in adults with obesity, or overweight plus a weight related health problem, and to lower the risk of heart attack, stroke and heart death in adults with heart disease and excess weight. The shot is also approved for teens 12 and older with obesity, and for a serious fatty liver disease called MASH with moderate to advanced liver scarring.[1]

Ozempic shots are approved for adults with type 2 diabetes to control blood sugar, lower heart risk in people with heart disease, and slow kidney decline in people with chronic kidney disease.[2] Rybelsus and Ozempic tablets are daily pills for blood sugar control and heart risk in adults with type 2 diabetes.[3]

Chemically, semaglutide is a large modified peptide (a chain of amino acids). PubChem lists its formula as C187H291N45O59.[4] Compounded semaglutide made by pharmacies is not FDA approved and is not the same as the brand products.[5]

Name
Semaglutide (Semaglutide)
Other names
Wegovy, Wegovy HD, Ozempic, Rybelsus
Type
Peptide drug (FDA approved)
CAS number
910463-68-2
Formula
C187H291N45O59
Molecular weight
About 4114 g/mol

What it does in the body

GLP-1 is a gut hormone that helps control appetite and how much you eat. Semaglutide is a lab made copy, about 94% the same as the human hormone, that binds to and switches on the same GLP-1 receptor. It is built to last long enough to be taken once a week as a shot or once a day as a pill.[1]

This is the biology, area by area. A change measured in the body, like a higher blood level, does not always mean a person feels a benefit. The claims check below covers that.

Fat and appetite

Measured in people

In a 20 week study of 72 adults with obesity, people on the weekly shot ate about 35% fewer calories at a lunch where they could eat as much as they wanted. They also reported less hunger and fewer food cravings, felt fuller, and lost 9.9% of their weight versus 0.4% on placebo.[6] The FDA label says more fat than lean mass is lost.[1]

Blood sugar and pancreas

Well established

Semaglutide makes the pancreas release more insulin and less glucagon, a hormone that raises blood sugar. It does this mainly when blood sugar is high, which the label calls a glucose dependent effect.[1] This is the basis for Ozempic and Rybelsus being approved to improve blood sugar control in type 2 diabetes.[2][3]

Stomach and gut

Measured in people

The label says semaglutide slows how fast food leaves the stomach.[1] In the 72 person study, a test of stomach emptying showed no clear delay by week 20.[6] Nausea, diarrhea, vomiting and constipation are the most common side effects, hitting roughly a quarter to nearly half of people in the weight trials.[1]

Heart and blood vessels

Measured in people

In SELECT, 17,604 adults with heart disease and excess weight but no diabetes were followed for about 40 months. Heart death, heart attack or stroke happened in 6.5% on the weekly shot versus 8.0% on placebo, a 20% lower risk.[7] Resting heart rate rises by about 1 to 4 beats per minute on average, and FDA says the reason for the heart benefit is not established.[1]

Kidneys

Measured in people

In FLOW, 3,533 adults with type 2 diabetes and chronic kidney disease took weekly Ozempic or placebo for a median of 3.4 years. The combined risk of kidney failure, a large drop in kidney function, or death from kidney or heart causes was 24% lower on the drug, and kidney function declined more slowly each year.[8]

Liver

Measured in people

In ESSENCE, an early look at 800 adults with MASH (fatty liver with inflammation) and moderate or advanced scarring, liver inflammation cleared without worse scarring in 62.9% after 72 weeks on the shot versus 34.3% on placebo. Scarring improved in 36.8% versus 22.4%.[9]

Brain and mood

Measured in people

Animal studies show semaglutide acts on nerve cells in brain areas that control food intake.[1] In people, a 9 week trial in 48 adults with alcohol use disorder found less craving and less drinking in a lab session.[10] But in 3,808 adults with early Alzheimer's disease, two years of semaglutide pills did not slow memory decline, even though some blood markers of the disease improved.[11]

How it works

Semaglutide acts like the body's own GLP-1 hormone by switching on the GLP-1 receptor, the same docking spot the natural hormone uses.[1]

  • The GLP-1 receptor is found in brain areas that control hunger, and animal studies show semaglutide reaches and activates nerve cells there. This helps explain lower appetite and food intake.[1]
  • The label also describes effects on insulin, on glucagon (a hormone that raises blood sugar) and on how fast the stomach empties, which together help lower blood sugar.[1]
  • How it lowers heart risk is not established, and its liver benefit may come partly from weight loss and partly from other pathways.[1]

The receptor action is well established. The exact reasons for the heart, kidney and liver benefits are still being studied.

What the research shows

We keep animal and human evidence apart. A result in animals is a reason to study something in people, not proof that it works in people.

Animal and lab studies

Animal studies matter mostly for safety, especially thyroid tumors

  • In two year studies, semaglutide raised the rate of thyroid C cell tumors in both male and female mice and rats, and thyroid cancers rose in male rats.[1]
  • In pregnant rats, rabbits and monkeys, it was linked to pregnancy loss, smaller fetuses and some birth defects, often along with weight loss in the mothers.[1]
  • In a mouse model of fatty liver disease, it improved liver fat, inflammation and scarring along with weight loss and lower food intake.[1]
  • Animal studies show the drug reaches brain areas that control hunger and switches on nerve cells there.[1]

Limit: No one knows yet whether the rodent thyroid finding applies to people, which is why the label carries a boxed warning.

Human studies

Strong evidence from large, placebo controlled trials

  • In STEP 1, 1,961 adults with obesity, or overweight plus a weight related health problem, took a weekly shot or placebo for 68 weeks. Average weight loss was 14.9% on semaglutide versus 2.4% on placebo, and 4.5% stopped because of stomach side effects versus 0.8% on placebo.[12]
  • In STEP UP, 1,407 adults with obesity took the higher Wegovy HD dose, the standard dose or placebo for 72 weeks. Counting everyone who started, weight fell 18.7%, 15.6% and 3.9%. Stomach side effects hit 70.8%, 61.2% and 42.8%, and odd skin feelings such as tingling or burning (dysesthesia) hit 22.9% on the higher dose versus 6.0% and 0.5%.[14]
  • In SURMOUNT-5, a head to head trial of 751 adults with obesity over 72 weeks, average weight loss was 13.7% on semaglutide versus 20.2% on tirzepatide.[20]
  • In STEP 5, 304 adults took a weekly shot or placebo for two years. Weight fell 15.2% versus 2.6%, and 77% versus 34% lost at least 5%. Stomach side effects, mostly mild to moderate, hit 82% versus 54%.[13]
  • In STEP 4, 803 adults who had already taken the drug for 20 weeks were split into two groups. Over the next 48 weeks, those who stayed on it lost another 7.9%, while those switched to placebo regained 6.9%.[17]
  • In the STEP 1 follow up, 327 people were tracked for a year after stopping. They regained about two thirds of the weight they had lost, ending a net 5.6% below their starting weight, and blood pressure and other heart measures drifted back.[16]
  • In a 20 week study of 72 adults with obesity, people on the shot ate about 35% fewer calories at a free choice lunch, felt less hungry and had fewer cravings than people on placebo.[6]
  • SELECT followed 17,604 adults with heart disease and excess weight for about 40 months. Major heart events happened in 6.5% on Wegovy versus 8.0% on placebo. Side effects made 16.6% stop the drug for good, versus 8.2% on placebo.[7]
  • FLOW followed 3,533 adults with type 2 diabetes and kidney disease for a median of 3.4 years. Major kidney events or kidney or heart death fell by 24% on Ozempic, and serious side effects were slightly less common than on placebo (49.6% versus 53.8%).[8]
  • In ESSENCE, a planned early look at 800 adults with MASH, liver inflammation cleared without worse scarring in 62.9% on the shot versus 34.3% on placebo, and weight fell 10.5% versus 2.0%.[9]
  • In a 9 week trial of 48 adults with alcohol use disorder, the weekly shot cut drinking in a lab session and weekly craving, but not the number of drinking days.[10]
  • In two trials of 3,808 adults with early Alzheimer's disease, a daily semaglutide pill taken for two years did not slow decline compared with placebo.[11]

Limit: Most trials were run by the maker, weight returns when the drug stops, and the liver approval is an accelerated approval that a longer trial must still confirm.[16][19]

Claims check

The most common claims about this compound, and what studies actually found. Verdicts rate the evidence, not whether you should use it.

Causes major weight loss

Shown in people

In STEP 1, 1,961 adults with obesity or overweight took a weekly shot or placebo for 68 weeks and lost 14.9% of their weight on average, versus 2.4% on placebo.[12] In STEP 5, 304 adults lost 15.2% over two years, versus 2.6% on placebo.[13] In STEP UP, 1,407 adults took the higher Wegovy HD dose, the standard dose or placebo for 72 weeks, and counting everyone who started, weight fell 18.7%, 15.6% and 3.9%.[14]

Lowers the risk of heart attack and stroke

Shown in people

SELECT enrolled 17,604 adults with heart disease and excess weight, but no diabetes, and followed them for about 40 months. Heart death, heart attack or stroke happened in 6.5% on the weekly shot versus 8.0% on placebo.[7] FDA approved Wegovy for this use in 2024.[15]

Protects the kidneys

Shown in people

In FLOW, 3,533 adults with type 2 diabetes and chronic kidney disease were followed for a median of 3.4 years. Serious kidney events or death from kidney or heart causes were 24% less likely on weekly Ozempic than placebo, and death from any cause was 20% less likely.[8] Ozempic is approved to slow kidney decline in this group.[2] This has not been tested in people without diabetes.

The weight stays off after you stop

No benefit in trials so far

In a STEP 1 follow up of 327 people, those on the drug had lost 17.3% by week 68. One year after stopping they had regained about two thirds of that loss, and most heart and blood sugar gains faded too.[16] In STEP 4, 803 adults took the drug for 20 weeks. Those switched to placebo regained 6.9% over the next 48 weeks, while those who stayed on it lost another 7.9%.[17]

You lose fat, not muscle

Mixed results

The FDA label says semaglutide lowers weight with more fat lost than lean mass (muscle, organs, water and bone), so some lean mass is still lost.[1] In a body scan substudy of 160 SURMOUNT-1 participants, 124 of them on tirzepatide, a related drug, about a quarter of the weight lost was lean mass, the same share seen on placebo.[18] Whether this lean loss changes strength or daily function has not been settled by these trials.

Treats fatty liver disease

Shown in people

In ESSENCE, 800 adults with MASH and moderate or advanced liver scarring took a weekly shot or placebo for 72 weeks. Liver inflammation cleared without worse scarring in 62.9% versus 34.3%, and scarring improved in 36.8% versus 22.4%.[9] This is an accelerated approval, so the longer part of the trial must still show it prevents serious liver outcomes.[19]

Cuts alcohol cravings

Mixed results

One small trial gave 48 adults with alcohol use disorder a weekly shot or placebo for 9 weeks. The drug group drank less in a lab drinking session, drank less on the days they drank, and reported less craving, but their number of drinking days and average daily drinks did not change.[10] Larger trials are needed.

Protects the brain from Alzheimer's disease

No benefit in trials so far

Two large trials gave 3,808 adults aged 55 to 85 with early Alzheimer's disease a daily semaglutide pill or placebo for two years. The drug did not slow memory and thinking decline, even though some blood markers of the disease improved.[11]

Known risks and side effects

  • Boxed warning for thyroid tumors. People with a personal or family history of medullary thyroid cancer or MEN 2 (an inherited tumor syndrome) should not use it. The warning is based on rodent studies.[1]
  • Stomach and gut side effects are very common. In the weight trials, nausea hit 44% versus 16% on placebo, diarrhea 30% versus 16%, vomiting 24% versus 6%, constipation 24% versus 11% and belly pain 20% versus 10%. About 6.8% stopped the shot because of side effects versus 3.2% on placebo.[1] In the long SELECT heart trial, 16.6% stopped for side effects versus 8.2%.[7]
  • Gallbladder, pancreas and kidney problems. Gallstones were reported in 1.6% on the shot versus 0.7% on placebo. The label also warns about inflamed pancreas (pancreatitis) and kidney injury from fluid loss.[1]
  • Heart rate, eyes and skin sensations. Resting heart rate rose by 1 to 4 beats per minute on average. In people with type 2 diabetes, eye damage from diabetes was reported in 4% versus 2.7%. Odd skin feelings (dysesthesia) hit 22% on the higher Wegovy HD dose versus 6% on the standard dose.[1] Europe's drug agency concluded in 2025 that a sudden optic nerve stroke called NAION, which can cause vision loss, is a very rare side effect, affecting up to 1 in 10,000 users.[21]
  • Compounded, fake and research only products. FDA has reports of people taking too much compounded semaglutide from vials, some needing hospital care.[22] FDA also says counterfeit Ozempic has been found in the US, and research only or salt form products are of unknown quality and are not the approved drug.[23]

Regulatory status

Today: Semaglutide is FDA approved as Wegovy, Ozempic and Rybelsus. FDA declared the shortage over in February 2025, its temporary leeway for pharmacies to make copies ended in spring 2025, and FDA says the salt forms have no lawful basis in compounding.[24][5][23] It is not banned in sport, but WADA keeps it on its 2027 monitoring list, which tracks use by athletes.[25]

  1. FDA approved Wegovy to lower the risk of heart attack, stroke and heart death in adults with heart disease and obesity or overweight.[15]
  2. FDA warned of dosing errors with compounded semaglutide, some leading to hospital stays.[22]
  3. FDA formally declared the semaglutide shortage resolved.[24]
  4. Leeway for state licensed pharmacies to copy semaglutide ended after a court declined to block FDA on April 24.[5]
  5. Leeway for outsourcing facilities ended on May 22.[5]
  6. Europe's drug safety committee concluded that the eye condition NAION is a very rare side effect of semaglutide.[21]
  7. FDA gave Wegovy accelerated approval for MASH with moderate to advanced liver scarring.[19]
  8. Novo Nordisk reported that its two Alzheimer's trials of semaglutide pills failed.[11]
  9. The Wegovy label removed its separate warning section on suicidal behavior and thoughts.[1]
  10. FDA approved Wegovy HD, a higher dose version.[26]
  11. WADA published its 2027 monitoring program, which again lists semaglutide for tracking in and out of competition.[25]
  12. FDA reported 990 adverse event reports tied to compounded semaglutide as of May 31, 2026, and noted these are likely undercounted.[23]

Sources

  1. Novo Nordisk. WEGOVY (semaglutide) injection and tablets: prescribing information. Revised 06/2026. FDA label
  2. Novo Nordisk. OZEMPIC (semaglutide) injection: prescribing information. Revised 10/2025. FDA label
  3. Novo Nordisk. RYBELSUS and OZEMPIC (semaglutide) tablets: prescribing information. Revised 01/2026. FDA label
  4. National Center for Biotechnology Information. PubChem Compound Summary for CID 56843331, Semaglutide. PubChem CID 56843331
  5. U.S. Food and Drug Administration. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize. Content current as of April 1, 2026. FDA
  6. Friedrichsen M, Breitschaft A, Tadayon S, Wizert A, Skovgaard D. The effect of semaglutide 2.4 mg once weekly on energy intake, appetite, control of eating, and gastric emptying in adults with obesity. Diabetes Obes Metab. 2021;23(3):754-762. PMID 33269530
  7. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med. 2023;389(24):2221-2232. PMID 37952131
  8. Perkovic V, Tuttle KR, Rossing P, et al. Effects of Semaglutide on Chronic Kidney Disease in Patients with Type 2 Diabetes. N Engl J Med. 2024;391(2):109-121. PMID 38785209
  9. Sanyal AJ, Newsome PN, Kliers I, et al. Phase 3 Trial of Semaglutide in Metabolic Dysfunction-Associated Steatohepatitis. N Engl J Med. 2025;392(21):2089-2099. PMID 40305708
  10. Hendershot CS, Bremmer MP, Paladino MB, et al. Once-Weekly Semaglutide in Adults With Alcohol Use Disorder: A Randomized Clinical Trial. JAMA Psychiatry. 2025;82(4):395. doi 10.1001/jamapsychiatry.2024.4789
  11. Novo Nordisk. evoke phase 3 trials did not demonstrate a statistically significant reduction in Alzheimer's disease progression. Company announcement, November 24, 2025. Company announcement
  12. Wilding JPH, Batterham RL, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989-1002. doi 10.1056/NEJMoa2032183
  13. Garvey WT, Batterham RL, Bhatta M, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28(10):2083-2091. doi 10.1038/s41591-022-02026-4
  14. Wharton S, Freitas P, Hjelmesæth J, et al. Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. Lancet Diabetes Endocrinol. 2025;13(11):949-963. PMID 40961952
  15. U.S. Food and Drug Administration. FDA Approves First Treatment to Reduce Risk of Serious Heart Problems Specifically in Adults with Obesity or Overweight. March 8, 2024. FDA news release
  16. Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564. doi 10.1111/dom.14725
  17. Rubino D, Abrahamsson N, Davies M, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414-1425. doi 10.1001/jama.2021.3224
  18. Look M, Dunn JP, Kushner RF, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. Diabetes Obes Metab. 2025;27(5):2720-2729. doi 10.1111/dom.16275
  19. U.S. Food and Drug Administration. FDA Approves Treatment for Serious Liver Disease Known as 'MASH'. August 15, 2025. FDA news release
  20. Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. N Engl J Med. 2025;393(1):26-36. doi 10.1056/NEJMoa2416394
  21. European Medicines Agency. PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy. June 6, 2025. EMA
  22. U.S. Food and Drug Administration. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. July 26, 2024. FDA safety alert
  23. U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Content current as of October 1, 2026. FDA
  24. U.S. Food and Drug Administration. Declaratory Order: Resolution of Shortages of Semaglutide Injection Products (Ozempic and Wegovy). February 21, 2025. FDA declaratory order
  25. World Anti-Doping Agency. The 2027 Monitoring Program. Published September 2026. WADA 2027 Monitoring Program
  26. U.S. Food and Drug Administration. FDA Approves Fourth Product Under National Priority Voucher Program, Higher Dose Semaglutide. March 19, 2026. FDA news release
Medical disclaimer

This page is educational information only. It is not medical advice and does not replace care from a licensed medical provider. Do not use this page to decide whether to take any substance. Talk to a licensed medical provider first.

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