Information and regulatory status checked on 6 November 2026. Approvals vary by country and can change.
Semaglutide became famous for weight loss, but its story began with a different question: how does the gut tell the pancreas that a meal has arrived?
Decades of research into that conversation led to medicines for type 2 diabetes, then treatments for obesity. Scientists are now testing medicines that act on two or three hormone pathways at once. Understanding that progression helps separate useful medical advances from exaggerated promises.
The discovery began long before the headlines
Researchers noticed that swallowing glucose produces a stronger insulin response than giving a comparable glucose exposure directly into the bloodstream. Gut signals help explain this “incretin effect.” Two important incretin hormones are glucose-dependent insulinotropic polypeptide, or GIP, and glucagon-like peptide-1, or GLP-1.
During the 1980s, work by several teams, including researchers Joel Habener, Svetlana Mojsov, Daniel Drucker and Jens Juul Holst, helped identify biologically active GLP-1 and explain its insulin-releasing effects. This was a shared scientific achievement built from molecular biology, physiology and clinical research. History of GLP-1 research
There was a practical obstacle: natural GLP-1 is broken down within minutes. A useful medicine needed to last longer. Exenatide, approved in the United States in 2005, was an early GLP-1 receptor medicine. Liraglutide and then semaglutide extended the approach. Novo Nordisk teams, including Lotte Bjerre Knudsen and Jesper Lau, modified the human GLP-1 molecule to resist breakdown and attach to the blood protein albumin. Semaglutide’s approximately one-week half-life made weekly injections possible. Its discovery paper appeared in 2015; U.S. approval for diabetes followed in 2017. Development of liraglutide and semaglutide · Original semaglutide discovery paper
What semaglutide does
Semaglutide activates the GLP-1 receptor, a cellular receiver for the hormone’s signal. It helps the pancreas release insulin when glucose is elevated, reduces inappropriate glucagon secretion and acts on appetite-related pathways. It also delays stomach emptying. These effects can improve glucose control and help people eat less. Semaglutide is not insulin, and the treatment effect is more complicated than simply making the stomach empty slowly. Ozempic prescribing information
The medicine’s formulation, dose, brand and approved purpose matter. Diabetes treatment and obesity treatment are not interchangeable prescriptions.
In the United States, Ozempic injection has type 2 diabetes indications, including particular cardiovascular and kidney risk-reduction indications. Wegovy has weight-management indications and, for specified patients, cardiovascular risk reduction. Wegovy injection also has an accelerated approval for certain adults with the liver disease MASH and moderate-to-advanced fibrosis, without cirrhosis. The oral and injectable products do not share every indication. Ozempic label · Wegovy label
This is a changing field: the U.S. approved oral Wegovy in December 2025 and a 7.2 mg injectable option, Wegovy HD, in March 2026. Older articles describing all obesity-dose semaglutide as a 2.4 mg weekly injection are therefore incomplete. These are regulatory facts, not instructions to change dose or switch products. Oral Wegovy approval · FDA announcement on Wegovy HD
One receptor, then two, then three
Semaglutide: GLP-1. This is a single-receptor agonist, meaning a medicine that activates one of these hormone receptors.
Tirzepatide: GIP and GLP-1. This single molecule activates both receptors. Its combined actions improve glucose regulation and reduce food intake. In the United States, tirzepatide is marketed as Mounjaro for type 2 diabetes and Zepbound for weight management. Zepbound is also approved for moderate-to-severe obstructive sleep apnoea in adults with obesity. Brand names and indications differ between countries. Mounjaro label · Zepbound label
Retatrutide: GIP, GLP-1 and glucagon. This investigational molecule adds glucagon-receptor activity. Glucagon normally helps the liver release glucose. Researchers are testing whether adding its actions can reduce food intake and increase energy use, while the incretin actions help balance glucose control. The contribution of each pathway in people is still being studied. Scientific rationale for triple agonism
Activating more receptors does not, by itself, establish that a medicine is better or safer for an individual. As of this article’s check, retatrutide remains investigational: Lilly’s 28 October 2026 statement says it is not approved by any regulator worldwide. Products sold online as “research peptides” are not approved retatrutide treatment. Retatrutide mechanism and current status
What the weight-loss numbers actually mean
Trial averages need their context. They are not predictions for a particular person.
- Semaglutide, STEP 1: Among 1,961 adults with obesity, or overweight plus a related condition, without diabetes, weekly semaglutide 2.4 mg plus lifestyle support produced average weight loss of 14.9% at 68 weeks, compared with 2.4% with placebo plus lifestyle support. STEP 1 trial
- Tirzepatide versus semaglutide, SURMOUNT-5: In a direct, open-label study of 751 adults without diabetes, participants received their maximum tolerated weekly dose of tirzepatide, 10 or 15 mg, or semaglutide, 1.7 or 2.4 mg. Average weight loss at 72 weeks was 20.2% versus 13.7%. This supports a comparison of those regimens in that population. It did not compare tirzepatide with the newer 7.2 mg semaglutide regimen. SURMOUNT-5 trial
- Retatrutide, TRIUMPH-1: Lilly’s May 2026 report described a phase 3 trial of 2,339 adults without diabetes. At 80 weeks, the 12 mg group had 25.0% average weight loss versus 3.9% with placebo in the analysis including outcomes regardless of treatment adherence. A different analysis, estimating results if participants remained on treatment without prohibited weight-management treatments, reported 28.3% versus 2.2%. These are different questions, not competing versions of the same statistic. Side effects led 11.3% of the 12 mg group to discontinue treatment, versus 4.9% with placebo. TRIUMPH-1 company report and analysis definitions
The last trial should not be placed beside the first two as a simple league table. Participants, doses, follow-up, comparison groups and statistical methods differ. Larger weight loss also does not automatically prove greater long-term cardiovascular benefit.
The next wave is broader than triple agonists
Researchers are also combining GLP-1 with amylin, another hormone involved in fullness and eating. Examples include CagriSema, a combination of semaglutide and the amylin analogue cagrilintide, and zenagamtide, formerly called amycretin. Current manufacturer sources describe these as investigational. Trial success and a regulatory application do not guarantee approval. CagriSema status · Zenagamtide development
Oral treatment is advancing too. Orforglipron should no longer be described as merely a future U.S. option: the FDA approved this GLP-1 tablet, branded Foundayo, for eligible adults needing weight management on 1 April 2026. That U.S. decision does not establish approval in India or elsewhere. FDA approval
A note for readers in India
Semaglutide and tirzepatide are already part of India’s prescription-treatment landscape. Wegovy injection was launched in June 2025, and Lilly’s India information lists tirzepatide for type 2 diabetes and chronic weight management in eligible adults. The appropriate product, indication and prescriber requirements must be checked against the current Indian approval, rather than copied from U.S. websites. Wegovy India announcement · Lilly India product information
India’s health ministry warned in March 2026 about unauthorised sales and misleading promotion, stressing specialist prescribing conditions and clinical supervision. An online seller’s listing is not evidence that its product or advertised use is approved. Ministry of Health and Family Welfare advisory
Benefits need a safety plan
Nausea, vomiting, diarrhoea and constipation are common with these approved medicines. Important warnings include pancreatitis, gallbladder problems, dehydration-related kidney injury and severe gastrointestinal problems. Low blood glucose is a particular concern when treatment is combined with insulin or sulfonylureas. Tell the surgical team before anaesthesia because delayed stomach emptying can matter. Zepbound prescribing information
U.S. semaglutide and tirzepatide labels contraindicate use in people with a personal or family history of medullary thyroid carcinoma or MEN2, and in people with relevant serious drug hypersensitivity. The thyroid warning comes from rodent findings; whether these medicines cause these tumours in humans is unknown. These medicines are not recommended for people with severe gastroparesis, a condition in which the stomach empties too slowly. Wegovy label · Mounjaro label
Weight-loss treatment is not appropriate during pregnancy. Discuss pregnancy plans in advance: semaglutide’s label advises stopping at least two months before a planned pregnancy. Tirzepatide can reduce oral contraceptive effectiveness, with additional or non-oral contraception advised for four weeks after starting and after each dose increase. Wegovy label · Mounjaro label
Eye symptoms also deserve attention. The UK regulator updated semaglutide information in February 2026 for the very rare eye condition NAION. Sudden loss of vision or rapidly worsening eyesight needs urgent medical assessment. MHRA safety update
Finally, the plan should include what happens if treatment stops. In a STEP 1 extension, participants regained about two-thirds of their previous weight loss within a year after both semaglutide and structured lifestyle support were withdrawn. This supports planning for ongoing care, rather than assuming a short course will permanently reset weight. STEP 1 extension
The practical takeaway: These medicines can be valuable treatments for appropriately selected patients. The right choice depends on the condition being treated, other illnesses and medicines, tolerability, access and a sustainable follow-up plan. A bigger trial percentage is not a prescription.
This article provides general education, not an individual diagnosis, prescription or dosing plan. Consult a qualified clinician and use the current locally approved product information.
#EYI #HealthExplained #GLP1 #Semaglutide #Tirzepatide #DiabetesEducation #ObesityCare #MedicalResearch
Sources and further reading
- History of GLP-1 research
- Development of liraglutide and semaglutide
- Original semaglutide discovery paper
- Ozempic prescribing information
- Wegovy label
- Mounjaro label
- Retatrutide mechanism and current status
- STEP 1 trial
- SURMOUNT-5 trial
- TRIUMPH-1 company report and analysis definitions
- FDA approval
- Ministry of Health and Family Welfare advisory
- MHRA safety update
- STEP 1 extension
