Hormone Journal

GLP-1 medications

Also known as: GLP-1 agonists, Ozempic, Wegovy, Mounjaro, semaglutide, tirzepatide

Medically reviewed by Hormone Journal Editorial Team · Last reviewed 2026-05-22

GLP-1 medications are injectable or oral drugs that mimic the gut hormone GLP-1 to lower blood sugar and reduce body weight by up to 15–22% in clinical trials.

What it is

GLP-1 medications are a class of prescription drugs that mimic glucagon-like peptide-1 (GLP-1), a gut-derived hormone, to lower blood glucose and reduce body weight — with semaglutide (Ozempic, Wegovy) producing average weight loss of roughly 15% and tirzepatide (Mounjaro) up to 22% of body weight in phase 3 trials. Also called GLP-1 receptor agonists, GLP-1 agonists, or incretin mimetics, these agents are approved in Canada by Health Canada for type 2 diabetes (semaglutide, liraglutide, dulaglutide, exenatide) and, more recently, for chronic weight management in adults with obesity or overweight plus at least one weight-related comorbidity (semaglutide as Wegovy; tirzepatide as Mounjaro). Approximately 27% of Canadian adults live with obesity and a further 36% with overweight, making this drug class one of the most consequential additions to Canadian prescribing in a generation.

The table below summarizes the agents most commonly encountered in Canadian practice:

DrugBrand name(s)Primary Health Canada indicationTypical dose rangeAverage weight loss (trial)
Semaglutide (injectable)Ozempic / WegovyT2DM / obesity0.5–2 mg weekly (Ozempic); up to 2.4 mg weekly (Wegovy)~15% (STEP 1)
TirzepatideMounjaroT2DM / obesity5–15 mg weekly~20–22% (SURMOUNT-1)
LiraglutideVictoza / SaxendaT2DM / obesity1.2–1.8 mg daily (Victoza); 3 mg daily (Saxenda)~8% (SCALE)
DulaglutideTrulicityT2DM0.75–4.5 mg weekly~3–4%
Semaglutide (oral)RybelsusT2DM7–14 mg daily~4–5%

Causes and mechanism

GLP-1 is secreted by L-cells in the small intestine in response to food. It acts on the pancreas to stimulate insulin release in a glucose-dependent manner (meaning it does not cause hypoglycaemia when blood sugar is normal), suppresses glucagon, slows gastric emptying, and signals satiety centres in the hypothalamus and brainstem. GLP-1 receptor agonists are synthetic analogues engineered to resist rapid enzymatic breakdown by dipeptidyl peptidase-4 (DPP-4), giving them a half-life of hours to days rather than the two minutes of native GLP-1. Tirzepatide is a dual agonist — it activates both GLP-1 receptors and glucose-dependent insulinotropic polypeptide (GIP) receptors, which appears to account for its larger weight-loss effect compared with GLP-1-only agents.

Symptoms and diagnosis

These medications treat conditions rather than produce symptoms, but candidates are typically identified through:

  • Type 2 diabetes — fasting glucose ≥7.0 mmol/L or HbA1c ≥6.5% on two occasions (Diabetes Canada criteria)
  • Obesity — body mass index (BMI) ≥30 kg/m², or ≥27 kg/m² with a comorbidity such as hypertension, dyslipidaemia, or obstructive sleep apnea
  • Cardiovascular risk — the SELECT trial (2023) showed semaglutide 2.4 mg reduced major adverse cardiovascular events by 20% in people with obesity and established cardiovascular disease but without diabetes

Baseline investigations before starting typically include HbA1c, fasting lipids, renal function, and thyroid-stimulating hormone (TSH). LifeLabs and Dynacare both offer these panels; most provincial labs process them under provincial health insurance.

Treatment options

All approved GLP-1 agents in Canada are prescription-only. Dosing follows a structured titration schedule — starting low and increasing every 4 weeks — to minimize gastrointestinal side effects (nausea, vomiting, diarrhea affect 30–50% of users, usually transiently).

Key clinical considerations:

  • GLP-1 agonists are not first-line for T2DM; Diabetes Canada guidelines position metformin as the preferred initial agent, with GLP-1 agonists added when HbA1c remains >1.5% above target, or when cardiovascular or renal protection is a priority.
  • For weight management, treatment is intended as long-term. The STEP 4 trial showed that stopping semaglutide after 20 weeks led to regain of roughly two-thirds of lost weight within one year.
  • Contraindications include personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (MEN2), and active or prior pancreatitis warrants caution.
  • Drug shortages have been a persistent issue in Canada since 2022; Health Canada has issued multiple shortage notices for Ozempic and Wegovy. Patients should confirm availability with their pharmacist before initiating.

Provincial drug coverage varies considerably. As of 2024, most provincial formularies (Ontario ODB, BC PharmaCare, Alberta Blue Cross) cover GLP-1 agents for T2DM with prior authorization, but coverage for obesity alone (Wegovy, Saxenda) is limited and often requires exceptional access applications. Out-of-pocket costs for Wegovy can exceed $400–$500 per month without coverage.

When to see a clinician in Canada

Seek assessment from a family physician, endocrinologist, or obesity medicine specialist if you have a BMI ≥30 (or ≥27 with comorbidities) and have not achieved adequate weight or glycaemic control with lifestyle changes alone. Referral to an endocrinologist is appropriate if HbA1c remains above target on two oral agents, or if thyroid nodules are detected on examination before starting therapy. Canadian telehealth platforms — including Felix, Maple, Cleo, Phoenix, and others — can facilitate initial prescribing assessments for eligible patients, though ongoing metabolic monitoring still requires periodic lab work and in-person or virtual follow-up.

Seek urgent care if you develop severe abdominal pain radiating to the back (possible pancreatitis), a neck lump with hoarseness (possible thyroid pathology), or signs of severe dehydration from persistent vomiting.

Limitations and open questions

Research is still emerging on several important questions:

  • Muscle mass loss — trials consistently show that 25–40% of weight lost on GLP-1 agents is lean mass rather than fat. Whether this is clinically harmful long-term, and whether resistance training fully mitigates it, is not yet established.
  • Mental health signals — the European Medicines Agency and Health Canada have both reviewed post-market reports of suicidal ideation and self-harm in GLP-1 users; as of 2024, neither agency has confirmed a causal link, but monitoring continues.
  • Fertility and pregnancy — GLP-1 agonists are not recommended during pregnancy. Their effect on fertility in women with polycystic ovary syndrome (PCOS) is under active study but no Canadian guideline has yet addressed this indication.
  • Long-term cardiovascular outcomes in obesity without diabetes — the SELECT trial is the first major evidence here; data beyond five years are not yet available.
  • Compounded semaglutide — Health Canada has not authorized compounded versions of semaglutide or tirzepatide. Their safety and bioequivalence are unverified, and Health Canada has issued warnings against their use.

FAQs

How is Ozempic different from Wegovy if they both contain semaglutide?

Both Ozempic and Wegovy contain semaglutide, but they are approved for different indications and use different dose ranges. Ozempic is approved in Canada for type 2 diabetes at doses up to 2 mg weekly, while Wegovy is approved for chronic weight management at a higher maintenance dose of 2.4 mg weekly. The higher dose is what drives the larger average weight loss of approximately 15% seen in the STEP 1 trial. Using Ozempic off-label for weight loss at lower doses is common due to Wegovy shortages, but the two products are not interchangeable without clinical guidance.

Are GLP-1 medications covered by provincial drug plans in Canada?

Coverage depends on the province and the indication. Most provincial formularies — including Ontario's ODB, BC PharmaCare, and Alberta Blue Cross — cover GLP-1 agonists for type 2 diabetes with prior authorization. Coverage for obesity alone (Wegovy, Saxenda) is much more limited and often requires an exceptional access or special authority application. Without coverage, Wegovy can cost $400–$500 or more per month out of pocket. Patients should check their provincial formulary and speak with their pharmacist or prescriber about access pathways.

What happens if I stop taking a GLP-1 medication?

Most of the weight lost on GLP-1 therapy returns after stopping. The STEP 4 trial found that participants who discontinued semaglutide after 20 weeks regained approximately two-thirds of their lost weight within one year, and most cardiometabolic improvements also reversed. This reflects the chronic nature of obesity as a condition rather than a failure of the medication. Current evidence supports treating obesity with GLP-1 agents as a long-term or indefinite therapy, similar to antihypertensives or statins.

Can GLP-1 medications affect mood or mental health?

This is an area of active regulatory review. The European Medicines Agency and Health Canada both examined post-market reports of suicidal ideation and self-harm in people taking GLP-1 receptor agonists, but as of 2024 neither agency has confirmed a causal relationship. Some case reports have documented worsened depression, and animal studies suggest GLP-1 receptors in the brain may influence mood circuits. Patients with a history of depression or suicidal ideation should discuss this uncertainty with their prescriber before starting, and any new or worsening mood symptoms should be reported promptly.

Do GLP-1 medications cause muscle loss, and how can it be minimized?

Yes, a meaningful proportion of weight lost on GLP-1 agents is lean mass. Trials suggest roughly 25–40% of total weight loss comes from muscle and other lean tissue rather than fat. This is not unique to GLP-1 drugs — it occurs with most caloric-deficit interventions — but the magnitude of weight loss makes it more clinically relevant here. Resistance training at least 2–3 times per week and adequate dietary protein intake (generally ≥1.2 g per kg of body weight per day) are the best-supported strategies to preserve muscle during treatment, though long-term data on outcomes are still limited.

Sources

All glossary termsUpdated 2026-05-22