The Comprehensive Semaglutide FAQ

Semaglutide is a synthetic peptide that mimics glucagon-like peptide-1 (GLP-1), a hormone naturally produced in the intestines. It activates GLP-1 receptors in the pancreas (promoting insulin secretion and suppressing glucagon), the brain (suppressing appetite), and the gastrointestinal tract (slowing gastric emptying). This multi-system activation leads to lower blood glucose, reduced appetite, and modest weight loss. Semaglutide is administered by subcutaneous injection once weekly.

Semaglutide is approved in Australia by the TGA for two indications: type 2 diabetes (brand name Ozempic) and chronic weight management (brand name Wegovy). Both are prescription-only medicines requiring a healthcare provider's prescription. The drug works by activating GLP-1 receptors, a mechanism shared by other GLP-1 agonists (liraglutide, dulaglutide, exenatide) but distinct from the newer dual GIP/GLP-1 agonists like tirzepatide.

For weight management, the STEP trials demonstrated mean weight loss of 10–15% from baseline with semaglutide 2.4 mg weekly (the Wegovy dose), compared to 2–3% with placebo. Response rates were high: approximately 86% of participants achieved ≥5% weight loss, 69% achieved ≥10%, and 35% achieved ≥15%. However, individual response varies—some lose >20% while others lose <5%. Predictive factors for superior response are not fully understood.

For type 2 diabetes, the SUSTAIN trials demonstrated HbA1c reductions of 1.0–1.8 percentage points depending on baseline HbA1c and dose (0.5–1.4 mg weekly, the Ozempic dose). Approximately 50–70% of participants achieved HbA1c targets (<7% or <53 mmol/mol). These reductions are among the largest achieved by any single diabetes medication. Additionally, SUSTAIN-6 demonstrated cardiovascular benefit (26% relative risk reduction in major cardiovascular events) in high-risk diabetes populations.

The most common side effects are gastrointestinal: nausea (25–35%), vomiting (5–10%), diarrhoea (10–20%), and constipation (10–15%). These are generally mild-to-moderate and transient, resolving within 4–8 weeks despite continued treatment. Serious adverse events (acute pancreatitis, acute cholecystitis, acute kidney injury) occur at similar frequencies in semaglutide and placebo groups, not supporting a causal relationship. No increased incidence of thyroid cancer has been observed despite the black-box warning based on rodent studies.

Overall, semaglutide has a favourable safety profile. Cardiovascular trials (SUSTAIN-6 and SELECT) demonstrated cardiovascular benefit, not harm. Heart rate increases by approximately 2–3 bpm; serious arrhythmias are rare. Patients with personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 should not use semaglutide. Pregnancy and nursing are contraindications. For most other populations, semaglutide is well-tolerated with appropriate monitoring.

In Australia, semaglutide is available by prescription from general practitioners and specialists. Ozempic (diabetes) is PBS-subsidised for eligible patients, with a patient co-payment of approximately AUD $50–$70 per script. Wegovy (weight management) is not PBS-listed and is accessed through private prescription, costing approximately AUD $400–$600 per month. Global access varies: semaglutide is approved in over 100 countries; availability and cost differ substantially by region.

Long-term effects beyond 2–3 years remain incompletely characterised; most clinical trials were 68–104 weeks in duration. Post-marketing surveillance suggests semaglutide is well-tolerated long-term, but real-world follow-up extends only 5–7 years. Weight regain occurs after discontinuation, with approximately 50–70% of lost weight regained within 1–2 years, indicating that semaglutide is a treatment requiring ongoing use rather than a cure. Long-term durability of diabetes control beyond 3 years is being investigated through extended follow-up trials.