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| GLP-1 | Semaglutide | |
|---|---|---|
| What it is | A natural gut hormone that helps lower blood sugar after meals; the same name is used for drugs that copy it12 | A GLP-1 analog and receptor agonist that shares 94% of its sequence with human GLP-13 |
| Active ingredient | The hormone itself, or in drugs a mimic such as exenatide, liraglutide, dulaglutide or semaglutide2 | Semaglutide, a chain of 31 amino acids (C187H291N45O59, 4113.58 g/mol)83 |
| Maker | Made in the intestine; drug versions come from more than one company, among them Novo Nordisk and Eli Lilly139 | Novo Nordisk, maker of Ozempic, Rybelsus and Wegovy364 |
| Form | In drugs: daily or weekly injections, or daily tablets1136 | Weekly injection (Ozempic, Wegovy) or daily tablet (Rybelsus, Ozempic tablets, Wegovy tablets)364 |
| Approved uses | Type 2 diabetes for most GLP-1 drugs, and weight management for some2 | Type 2 diabetes, weight reduction, cardiovascular and kidney risk reduction, and MASH, split across its brands346 |
| Dosing schedule | Set per drug, from daily (Saxenda, stepped up to 3 mg) to weekly (Ozempic)113 | Ozempic 0.25 to 2 mg weekly, Wegovy up to 7.2 mg weekly, tablets 1.5 to 25 mg daily; the prescriber sets the dose346 |
| First US approval | 2005, the first GLP-1 receptor agonist (Byetta)2 | December 5, 2017, as Ozempic5 |
Key differences
Agonist, not inhibitor
"GLP-1" can mean the hormone or the drugs built to copy it. The hormone comes from the intestine. It lowers blood sugar after a meal and works on the parts of the brain that govern appetite and food intake.1 Semaglutide is one of the copies. It selectively binds to and activates the GLP-1 receptor, the same target the natural hormone uses.4 That makes it a receptor agonist: it switches the receptor on. It is not a GLP-1 inhibitor, and PubChem lists its FDA pharmacologic class as GLP-1 receptor agonist.8
Through the receptor, semaglutide raises insulin release and lowers glucagon, both in a glucose-dependent way. It also causes a minor delay in stomach emptying soon after a meal.3 GLP-1 is a natural regulator of appetite and calorie intake, and its receptor sits in brain areas involved in appetite. Semaglutide lowers calorie intake, likely by acting on appetite, and in animal studies it reached and activated neurons in brain regions that regulate food intake.4
How semaglutide differs from the hormone
Semaglutide is a modified copy. Compared with human GLP-1, it has two amino acid substitutions: Aib at position 8 and Arg at position 34.7 The lysine at position 26 carries a C18 fatty diacid, attached through a hydrophilic spacer.3 The label names albumin binding as the main reason semaglutide lasts so long, and says it is also stabilized against breakdown by the DPP-4 enzyme. Its elimination half-life is about 1 week.34 The finished molecule still shares 94% of its sequence with the human hormone. In the approved products, its peptide backbone is made by yeast fermentation.3
The weekly design was the goal from the start. The 2015 discovery paper set out to make a once-weekly analogue by raising albumin binding and securing stability against breakdown, and it selected semaglutide as the optimal candidate. In mini-pigs, semaglutide had a plasma half-life of 46.1 hours after an IV dose and a mean residence time of 63.6 hours after an injection under the skin.7 In people, it stays in the circulation for about 5 to 7 weeks after the last 2.4 mg or 7.2 mg injection.4
The route changes the dose. About 89% of an injected dose reaches the bloodstream, against about 1% to 2% of a tablet dose.4 So tablet doses are much larger: approved tablets go up to 25 mg a day, while approved injections run from 0.25 mg to 7.2 mg once a week.463 In adults with overweight or obesity and no type 2 diabetes, the Wegovy label predicts that a 25 mg daily tablet gives semaglutide levels comparable to a 2.4 mg weekly injection.4
Semaglutide among the GLP-1 drugs
FDA's 2024 list of approved GLP-1 receptor agonists shows how crowded the class is. It runs from Byetta (2005) through Victoza (2010), Trulicity and Saxenda (2014), Adlyxin (2016), Ozempic (2017), Rybelsus (2019) and Wegovy (2021) to Mounjaro (2022) and Zepbound (2023).2 Three of those brands contain semaglutide: Ozempic, Rybelsus and Wegovy.2 The 2026 tablet label adds Ozempic tablets, so the Ozempic name now covers a daily pill as well as the weekly pen.6 Tirzepatide, in Mounjaro and Zepbound, is on the list too, but its label calls it a GIP receptor and GLP-1 receptor agonist because it acts on a second hormone receptor.9
Semaglutide has been tested head to head against liraglutide, an older GLP-1 drug, as both an injection and a tablet. In STEP 8, 338 adults with overweight or obesity and no diabetes were randomized to weekly semaglutide 2.4 mg, daily liraglutide 3.0 mg or placebo for 68 weeks. Mean weight change was -15.8% on semaglutide vs -6.4% on liraglutide. Treatment was stopped by 13.5% vs 27.6%, and stomach and gut side effects were about as common in both groups (84.1% vs 82.7%).10 Liraglutide 3 mg a day is the Saxenda maintenance dose, reached in weekly steps from 0.6 mg.11 In a 26-week label trial of 711 adults with type 2 diabetes, Rybelsus 14 mg tablets lowered HbA1c by 1.2 percentage points vs 1.1 for daily liraglutide 1.8 mg injections, which met the test for non-inferiority, with more weight loss (4.4 kg vs 3.1 kg).6
What semaglutide shares with the class
The Ozempic label shows the main safety points. It carries a boxed warning: semaglutide caused thyroid C-cell tumors in mice and rats, it is unknown whether it does so in humans, and it must not be used with a personal or family history of medullary thyroid carcinoma or MEN 2.3 Stomach and gut effects are the most common side effects, and the label raises the dose slowly to reduce them.3
Rates rise with dose. On Ozempic, nausea affected 15.8% of people on 0.5 mg and 20.3% on 1 mg, vs 6.1% on placebo.3 In Wegovy's weight trials at 2.4 mg, it affected 44% vs 16% on placebo.4 These figures come from different trials, so they show a pattern rather than a head-to-head result. FDA's January 2026 review of 91 placebo-controlled trials with 107,910 patients found no increased risk of suicidal thoughts or behavior with GLP-1 receptor agonists.1
Which page to read next
Begin with What is GLP-1?, which covers the hormone and its drug class, and GLP-1 dosage for label schedules across the class. For the molecule, read What is Semaglutide? and Semaglutide side effects; Semaglutide and weight loss covers the weight trials. Related pairs: Ozempic vs semaglutide, semaglutide vs Wegovy and GLP-1 vs Mounjaro. The comparisons hub lists the rest.
Frequently asked questions
Is semaglutide a GLP-1 inhibitor?
No. Semaglutide is a GLP-1 receptor agonist, which means it switches the receptor on rather than blocking it. It selectively binds to and activates the GLP-1 receptor, the same target the body's own hormone uses.4 Through that receptor it raises insulin release and lowers glucagon, both in a glucose-dependent way, and causes a minor delay in stomach emptying soon after meals.3
Is semaglutide the same as GLP-1?
No, but it is closely modeled on it. Semaglutide shares 94% of its sequence with human GLP-1.3 Compared with the hormone, it has two swapped amino acids, Aib at position 8 and Arg at position 34,7 and a C18 fatty diacid on the lysine at position 26. Binding to albumin in the blood is the main reason it lasts, and it is also stabilized against breakdown by the DPP-4 enzyme, giving an elimination half-life of about 1 week.34 The natural hormone is released by the intestine and helps lower blood sugar after eating.1
What type of medicine is semaglutide?
A peptide drug: PubChem describes a linear chain of 31 amino acids and lists its FDA pharmacologic class as GLP-1 receptor agonist.8 In the US it is the active ingredient of Novo Nordisk's prescription brands Ozempic and Rybelsus, for type 2 diabetes, and Wegovy, for weight reduction, cardiovascular risk and a liver disease called MASH.364 The forms are weekly injections and daily tablets, and the prescriber sets the dose.36
Is liraglutide better than semaglutide?
One head-to-head trial favored semaglutide for weight. In STEP 8, 338 adults with overweight or obesity and no diabetes were randomized to weekly semaglutide 2.4 mg, daily liraglutide 3.0 mg or placebo for 68 weeks. Mean weight change was -15.8% on semaglutide vs -6.4% on liraglutide, and 13.5% vs 27.6% stopped treatment.10 Liraglutide 3 mg a day is the Saxenda dose.11 A trial average does not decide which drug suits one person; that is a choice for the patient and prescriber.
Why is semaglutide given once a week?
It was designed for weekly dosing. The discovery paper set out to raise albumin binding and secure stability against breakdown, and semaglutide was selected as the best once-weekly candidate.7 The Ozempic label names albumin binding as the main reason for its long half-life and says it is stabilized against the DPP-4 enzyme.3 The elimination half-life is about 1 week, so after the last 2.4 mg or 7.2 mg injection semaglutide stays in the circulation for about 5 to 7 weeks.4 In mini-pigs, its plasma half-life was 46.1 hours after an IV dose.7
Are all GLP-1 drugs made from semaglutide?
No. FDA's 2024 list of approved GLP-1 receptor agonists includes exenatide (Byetta, Bydureon BCise), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity) and lixisenatide (Adlyxin), alongside the semaglutide brands Ozempic, Rybelsus and Wegovy.2 Tirzepatide (Mounjaro, Zepbound) is also on that list, but its label calls it a GIP receptor and GLP-1 receptor agonist, because it acts on a second hormone receptor.29
Written by D2C Peptides Editorial Team.
Pending qualified review.
Updated .
Sources
- FDA Requests Removal of Suicidal Behavior and Ideation Warning from Glucagon-Like Peptide-1 Receptor Agonist (GLP-1 RA) Medications (Drug Safety Communication, 01-13-2026). U.S. Food and Drug Administration, 2026.
- Update on FDA's ongoing evaluation of reports of suicidal thoughts or actions in patients taking a certain type of medicines approved for type 2 diabetes and obesity (Drug Safety Communication, 01-11-2024). U.S. Food and Drug Administration, 2024.
- OZEMPIC (semaglutide) injection, solution: prescribing information, Medication Guide and Instructions for Use (Revised 5/2026, SPL version 20). U.S. National Library of Medicine, DailyMed (label from Novo Nordisk), 2026.
- WEGOVY (semaglutide) injection and tablets: prescribing information (Revised 6/2026). U.S. National Library of Medicine, DailyMed (label from Novo Nordisk), 2026.
- Drugs@FDA: NDA 209637 OZEMPIC product and approval history. U.S. Food and Drug Administration, 2026.
- OZEMPIC (oral semaglutide) tablet; RYBELSUS (oral semaglutide) tablet: prescribing information (Revised 1/2026). U.S. National Library of Medicine, DailyMed (label from Novo Nordisk), 2026.
- Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide (Lau et al.), PubMed abstract PMID 26308095. Journal of Medicinal Chemistry (abstract via NLM PubMed E-utilities), 2015.
- Semaglutide, PubChem CID 56843331: record descriptions (ChEBI, NCI Thesaurus, LiverTox, FDA Pharmacologic Class). PubChem, U.S. National Library of Medicine.
- MOUNJARO (tirzepatide) injection Prescribing Information, Medication Guide and Instructions for Use, revised 08/2026 (NDA 215866/S-044, S-045). U.S. Food and Drug Administration (Drugs@FDA), 2026.
- Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes (STEP 8; Rubino et al.), PubMed abstract PMID 35015037. JAMA (abstract via NLM PubMed E-utilities), 2022.
- SAXENDA (liraglutide) injection, prescribing information (revised 6/2026). U.S. National Library of Medicine, DailyMed (label by Novo Nordisk), 2026.