GLP-1 Agonists: What They Are & What Makes Them Unique

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Curious about the science behind today’s most talked-about diabetes and weight-management treatments? Our new, four-part blog series on GLP-1 Agonists will break down everything you need to know — from how these drugs work, to their real-world results, side effects, and what’s coming next in the pipeline.

GLP-1 stands for glucagon-like peptide-1. It’s an incretin hormone produced in the gut that stimulates insulin secretion (when glucose is high), suppresses glucagon, slows gastric emptying and increases feeling of fullness.

GLP-1 receptor agonists (GLP-1 RAs) are drugs that mimic or augment the effect of GLP-1. They are used mainly in patients with type 2 diabetes mellitus (T2DM) for improving glycemic control, and many are also approved (or used off-label) for weight management / obesity.

They generally have a low risk of causing hypoglycemia when used alone (because their insulin-stimulating effect depends on blood glucose). They also can help reduce appetite and lead to weight loss.

Currently Available and Approved GLP-1s

The below table shows a summary of GLP-1 receptor agonists approved by U.S. and Canadian federal health authorities as of mid-2025, the primary indication they are used for, and key differentiators between them:

Drug (brand-name / generic)	Manufacturer(s)	Frequency / Route	Approved Indications*	Key Notes / Advantages & Limitations
Semaglutide — Ozempic® (injection)	Novo Nordisk	Once weekly subcutaneous injection	T2DM; also cardiovascular risk reduction in T2DM in certain patients with cardiovascular disease (CVD).	Very effective at lowering HbA1c; good for weight loss though full obesity dose = different brand (see Wegovy). Some GI side effects.
Semaglutide — Wegovy® (higher dose injection)	Novo Nordisk	Once weekly SC injection	For weight management / obesity (in adults and adolescents 12+ in many regions) with or without T2DM.	The obesity-approved dose is higher than the dose in diabetes treatment. Tend to get more weight loss. More cost and possibly more side effects.
Semaglutide — Rybelsus® (oral)	Novo Nordisk	Daily oral tablet	T2DM only (for glycemic control)	Oral option is helpful for those who dislike or cannot use injections. Bioavailability is lower; may need specific administration instructions (e.g., empty stomach, water only, waiting before food) to maximize absorption. Side effects typically similar GI types.
Liraglutide — Victoza®	Novo Nordisk	Daily injection	T2DM; also reduces cardiovascular events in some patients.	Has been around longer, good track record. Dose is daily rather than weekly, which some may find less convenient.
Liraglutide — Saxenda®	Same (higher dose)	Daily injection	For obesity / weight management (adults (and adolescents depending on region) meeting obesity or overweight + comorbidity criteria)	The obesity dose is higher; side effects generally similar (GI, etc.). Requires daily administration.
Dulaglutide — Trulicity®	Eli Lilly	Once weekly injection	T2DM; also has cardiovascular risk-reduction evidence in T2DM with risk factors.	Weekly dosing is convenient. Less heavy data for obesity (versus some others) though weight loss is a side effect.
Exenatide — Byetta® (twice daily) & Bydureon® / Bydureon BCise (extended-release weekly)	AstraZeneca	Twice daily for Byetta; once weekly for Bydureon ER/BCise	T2DM glycemic control	The twice daily version has more GI side effects and requires more frequent dosing; extended release is more convenient. Less potent in weight loss than some newer agents. Note: some formulations may not be marketed in all countries.
Lixisenatide — Adlyxin® (U.S.) / Adlyxine (other regions)	Sanofi	Daily injection	T2DM glycemic control	Short-acting; useful in certain situations like postprandial glucose spikes; fewer data for weight loss vs others.
Tirzepatide — Mounjaro® (for diabetes) / Zepbound® (for weight)	Eli Lilly	Once weekly injection	Dual GLP-1 / GIP receptor agonist. Approved for T2DM (Mounjaro) and obesity (Zepbound) in adults.	Among the most potent for weight loss. Dual-mechanism may offer advantages in efficacy. Side effects tend to be more pronounced especially GI; cost is higher; long-term safety still being accumulated.

In Part 2, we evaluate how to choose between GLP-1 molecules, using a goal-based approach. It’s releasing exclusively on our blog November 6th, so make sure to add us to your bookmarks to stay up to date!: https://joinastudy.ca/canadian-health-blog/

Sources

https://my.clevelandclinic.org/health/treatments/13901-glp-1-agonists

https://www.canada.ca/en/health-canada/services/drugs-health-products/medeffect-canada/health-product-infowatch/december-2024.html

https://pubmed.ncbi.nlm.nih.gov/26371721/

https://www.endocrinologyadvisor.com/ddi/glp-1-agonists/

https://hopkinsdiabetesinfo.org/medications-for-type-2-diabetes-glp-1-agonists/

https://www.ncbi.nlm.nih.gov/books/NBK551568/

https://www.ncbi.nlm.nih.gov/books/n/rc72848269830370/

https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-shortages/information-consumers/supply-notices/ozempic.html

https://www.practicenursing.com/content/clinical/glp-1-receptor-agonists-and-their-role-in-managing-type-2-diabetes

https://www.drugs.com/medical-answers/glp-1-drug-best-weight-loss-3579236/

https://www.primetherapeutics.com/en/glp-1-pipeline-update-november-2024