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Medical Weight Loss questions

Answers drawn from published trials and FDA labels. Treatment depends on an exam by a licensed medical provider.

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Answers

What patients ask

How much weight do people lose on semaglutide?

In STEP 1, adults on semaglutide 2.4 mg weekly lost a mean 14.9% of body weight at 68 weeks, against 2.4% on placebo. Half lost 15% or more.[1]

Is tirzepatide stronger than semaglutide?

In SURMOUNT-5, 751 adults on the highest tolerated dose lost 20.2% on tirzepatide and 13.7% on semaglutide at 72 weeks.[1]

What is the difference between Ozempic and Wegovy?

Both are semaglutide. Ozempic is labeled for type 2 diabetes. Wegovy is labeled for chronic weight management and for cardiovascular risk reduction. Mounjaro and Zepbound are the same pair for tirzepatide.[1][2][3]

Is compounded semaglutide the same as Wegovy?

No. Compounded drugs are not FDA approved or reviewed for safety, effectiveness or quality. FDA warns that some use salt forms, semaglutide sodium or acetate, which are different active ingredients.[1]

Can pharmacies still compound semaglutide and tirzepatide?

FDA declared the tirzepatide shortage resolved on December 19, 2024 and the semaglutide shortage on February 21, 2025. Grace periods ended by May 22, 2025. Pharmacies may not regularly make essentially copies of an approved drug unless a prescriber documents a significant difference for a patient.[1]

What happens when I stop the injections?

In the STEP 1 extension, people regained two-thirds of the lost weight one year after stopping semaglutide. In SURMOUNT-4, people switched off tirzepatide regained 14.0%.[1][2]

What are the most common side effects?

Gastrointestinal: nausea 44%, diarrhea 30%, vomiting 24% and constipation 24% in Wegovy trials. With tirzepatide they occurred mostly while the dose was being raised.[1][2]

Do GLP-1 drugs cause thyroid cancer?

They cause thyroid C-cell tumors in rodents. It is unknown whether they do in humans. They carry a boxed warning and are not used with a personal or family history of medullary thyroid carcinoma or MEN 2.[1][2]

Do I lose muscle on these drugs?

Some. In a 22-trial meta-analysis, lean mass was about 25% of the weight lost on GLP-1 drugs.[1]

Do I need to tell my surgeon I take a GLP-1 drug?

Yes. Current Ozempic and Zepbound labels report pulmonary aspiration during general anesthesia or deep sedation and tell patients to inform providers of any planned surgery or procedure.[1][2]

Sources

Sources

Checked 2026-10-25. Every fact links to its source.

  1. Wilding et al., STEP 1: once-weekly semaglutide in adults with overweight or obesity, N Engl J Med 2021
  2. Jastreboff et al., SURMOUNT-1: tirzepatide once weekly for the treatment of obesity, N Engl J Med 2022
  3. Pi-Sunyer et al., SCALE: 3.0 mg of liraglutide in weight management, N Engl J Med 2015
  4. Rubino et al., STEP 4: continued semaglutide vs placebo for weight maintenance, JAMA 2021
  5. Wilding et al., weight regain after withdrawal of semaglutide: STEP 1 trial extension, 2022
  6. Lincoff et al., SELECT: semaglutide and cardiovascular outcomes in obesity without diabetes, N Engl J Med 2023
  7. Aronne et al., SURMOUNT-4: continued tirzepatide for maintenance of weight reduction, JAMA 2024
  8. Aronne et al., SURMOUNT-5: tirzepatide compared with semaglutide for obesity, N Engl J Med 2025
  9. Gadde et al., CONQUER: low-dose controlled-release phentermine plus topiramate, Lancet 2011
  10. Greenway et al., COR-I: naltrexone plus bupropion in overweight and obese adults, Lancet 2010
  11. Holst et al., truncated glucagon-like peptide I, an insulin-releasing hormone from the distal gut, 1987
  12. Mojsov, Weir, Habener, insulinotropin: glucagon-like peptide I (7-37) stimulates insulin release, 1987
  13. Eng et al., isolation and characterization of exendin-4 from Heloderma suspectum venom, 1992
  14. Connolly et al., valvular heart disease associated with fenfluramine-phentermine, N Engl J Med 1997
  15. He et al., GLP-1 receptor agonists and risk of gallbladder and biliary diseases, meta-analysis, JAMA Intern Med 2022
  16. Lau et al., discovery of the once-weekly GLP-1 analogue semaglutide, J Med Chem 2015
  17. Lambson et al., administration errors of compounded semaglutide reported to a poison control center, 2023
  18. Karakasis et al., GLP-1 receptor agonists and co-agonists and body composition, network meta-analysis, 2025
  19. Drucker, mechanisms of action and therapeutic application of glucagon-like peptide-1, Cell Metab 2018
  20. FDA, WEGOVY (semaglutide) injection prescribing information, 2021
  21. FDA, WEGOVY NDA 215256 approval letter, 2021
  22. FDA, ZEPBOUND (tirzepatide) injection prescribing information, 2023
  23. FDA, ZEPBOUND NDA 217806 approval letter, 2023
  24. FDA news release, FDA approves new medication for chronic weight management (Zepbound), November 8, 2023
  25. FDA news release, first treatment to reduce risk of serious heart problems in adults with obesity or overweight (Wegovy), March 8, 2024
  26. FDA, SAXENDA (liraglutide) injection prescribing information, 2014
  27. FDA, SAXENDA NDA 206321 approval letter, 2014
  28. FDA, QSYMIA (phentermine and topiramate extended-release) prescribing information, 2012
  29. FDA, CONTRAVE (naltrexone and bupropion extended-release) prescribing information, 2014
  30. FDA, ADIPEX-P (phentermine hydrochloride) prescribing information
  31. FDA, OZEMPIC (semaglutide) injection prescribing information, 2017
  32. FDA, MOUNJARO (tirzepatide) injection prescribing information, 2022
  33. FDA, BYETTA (exenatide) injection prescribing information, 2005
  34. FDA, FDA's concerns with unapproved GLP-1 drugs used for weight loss, content current as of 10/01/2026
  35. FDA, FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize, updates 2024-2026
  36. FDA, dosing errors associated with compounded injectable semaglutide products
  37. FDA, FDA warns consumers not to use counterfeit Ozempic (semaglutide), December 5, 2025
  38. FDA openFDA drug label API, ZEPBOUND current label (effective 2026-08-28)
  39. FDA openFDA drug label API, OZEMPIC current label (effective 2026)