Semaglutide
Semaglutide is a long-acting copy of the gut hormone GLP-1. It is a prescription medicine approved for type 2 diabetes (Ozempic, Rybelsus) and for weight management and cardiovascular risk reduction in people with obesity (Wegovy).
Reference information, not medical advice. Enhanced Training Studio doesn't sell, supply or recommend any substance. Doses are left out on purpose: only a prescriber can set one. How this library is written.
What it is
Semaglutide is a man-made version of glucagon-like peptide-1 (GLP-1), a hormone released by the gut after eating. It is made by Novo Nordisk and sold as an injection (Ozempic, Wegovy) and as tablets (Rybelsus, Ozempic tablets and Wegovy tablets in the US). It is a prescription-only medicine and should only be used under medical supervision.
How it works
Semaglutide has 94% sequence similarity to human GLP-1 and acts on the GLP-1 receptor [2]. It raises insulin release and lowers glucagon release, both only when blood glucose is high, and it slows early stomach emptying after meals [2]. It appears to regulate appetite by increasing feelings of fullness and reducing hunger and food intake [4].
Semaglutide binds to the blood protein albumin, which gives it an elimination half-life of about one week, so it stays in the circulation for about five weeks after the last dose [2]. After injection, peak levels are reached in one to three days [2]. The tablets contain an absorption enhancer (SNAC), and only a small fraction of each tablet is absorbed, mainly in the stomach [3].
Approved medical uses
- Type 2 diabetes: to improve blood glucose control alongside diet and exercise, to lower the risk of major cardiovascular events in people with heart disease, and (Ozempic injection) to lower the risk of kidney disease getting worse in people with chronic kidney disease [2, 3].
- Weight management: in adults with obesity, or overweight with at least one weight-related condition, and in adolescents aged 12 and over with obesity (Wegovy) [1, 4].
- Cardiovascular risk reduction: in adults with established cardiovascular disease and obesity or overweight (Wegovy) [1, 5].
- MASH: a form of fatty liver disease with moderate to advanced scarring, under accelerated approval in the US (Wegovy injection) [1, 6].
What the research shows
- In a 68-week trial of 1,961 adults with obesity or overweight, people on semaglutide lost about 15% of body weight on average, compared with about 2% on placebo. About 84% lost at least 5% of their weight, compared with 31% on placebo [4].
- When people who had lost weight on semaglutide were switched to placebo, they regained around 7% of body weight over 48 weeks, while those who continued lost a further 8% [4]. This suggests the effect depends on continued treatment.
- The SELECT trial followed more than 17,600 adults with heart disease and overweight or obesity but without diabetes. Major cardiovascular events (heart attack, stroke or cardiovascular death) happened in 6.5% of people on semaglutide and 8% on placebo [5].
- In people with MASH and liver scarring, 63% on semaglutide had resolution of MASH without worsening scarring at 72 weeks, compared with 34% on placebo. Whether this leads to fewer liver failures or deaths is still being studied [6].
Known risks and side effects
- Common: nausea, diarrhoea, vomiting, constipation, stomach pain, headache and tiredness [1, 4].
- Thyroid tumours: semaglutide caused thyroid C-cell tumours in rodents. It is not known whether this happens in humans, but it must not be used by people with a personal or family history of medullary thyroid cancer or MEN 2 [1].
- Pancreatitis: acute pancreatitis, including rare severe and fatal cases, has been reported. The MHRA strengthened this warning in 2026 [1, 8].
- Other serious risks: gallbladder disease such as gallstones, kidney injury from dehydration, low blood sugar when used with insulin or sulfonylureas, worsening diabetic eye disease, a faster heart rate, allergic reactions and breathing in stomach contents during anaesthesia [1, 2].
- Eye: the EMA concluded that a sudden-onset optic nerve condition (NAION) is a very rare side effect, affecting up to 1 in 10,000 people [7].
- Pregnancy: it should be stopped when pregnancy is recognised and at least two months before a planned pregnancy, because of its long half-life [1].
- Unlicensed products: the FDA says compounded semaglutide is not reviewed for safety, effectiveness or quality, and it has received reports of harm from dosing errors and fraudulent products [9]. The MHRA has warned about fake semaglutide pens, some of which appeared to contain insulin and led to hospital admissions [10].
Blood tests commonly monitored
- Blood glucose: in people with diabetes, especially when combined with insulin or sulfonylureas [1, 2].
- Kidney function: in people who have vomiting, diarrhoea or dehydration [1, 2].
- Calcitonin: the label notes that routine calcitonin testing has uncertain value for detecting thyroid cancer; raised levels are investigated further [1].
- Lipase and amylase: raised levels are seen in some people; their meaning without symptoms of pancreatitis is unclear [1].
If you and your doctor are monitoring treatment, Enhanced Training Studio keeps a private log on your phone: what you take and when, your blood test results over time, and how you feel. How tracking works.
Sources
- US Food and Drug Administration / Novo Nordisk. Wegovy (semaglutide) injection and tablets: prescribing information. DailyMed, US National Library of Medicine, revised 2026. DailyMed: Wegovy
- US Food and Drug Administration / Novo Nordisk. Ozempic (semaglutide) injection: prescribing information. DailyMed, US National Library of Medicine, revised 2026. DailyMed: Ozempic
- US Food and Drug Administration / Novo Nordisk. Rybelsus and Ozempic (semaglutide) tablets: prescribing information. DailyMed, US National Library of Medicine, revised 2026. DailyMed: Rybelsus and Ozempic tablets
- European Medicines Agency. Wegovy (semaglutide): an overview of Wegovy and why it is authorised in the EU. EMA, 2023. EMA: Wegovy medicine overview
- US Food and Drug Administration. FDA approves first treatment to reduce risk of serious heart problems specifically in adults with obesity or overweight. FDA, 2024. FDA press announcement
- US Food and Drug Administration. FDA approves treatment for serious liver disease known as "MASH". FDA, 2025. FDA: MASH approval
- European Medicines Agency. PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy. EMA, 2025. EMA: NAION and semaglutide
- Medicines and Healthcare products Regulatory Agency. GLP-1 and dual GIP/GLP-1 receptor agonists: strengthened warnings on the risk of acute pancreatitis. Drug Safety Update, 2026. MHRA Drug Safety Update
- US Food and Drug Administration. FDA's concerns with unapproved GLP-1 drugs used for weight loss. FDA, updated 2026. FDA: unapproved GLP-1 drugs
- Medicines and Healthcare products Regulatory Agency. MHRA warns of unsafe fake weight loss pens. GOV.UK, 2023. MHRA: fake weight loss pens
Related
Last reviewed 7 October 2026. General information, not medical advice. Found a mistake? Email [email protected].