GLP-1 Agonists: Uses, Side Effects, and Why People Stop

There’s a reason the phrase “Ozempic face” entered the cultural lexicon — GLP-1 agonists have transformed how millions manage weight and blood sugar. But the real story is less about celebrity buzz and more about the daily decisions people make: which drug to choose, whether the side effects are worth it, and what happens when you stop. This guide examines the evidence, from clinical trials to patient experiences, with a particular focus on what’s available in Ireland.

Primary indications: Type 2 diabetes, obesity ·
Common brand names: Ozempic, Wegovy, Victoza, Saxenda, Trulicity ·
Route of administration: Subcutaneous injection ·
Year first approved: 2005 (exenatide)

Key facts about GLP-1 agonists are listed below.

What drugs are GLP-1 agonists?

GLP-1 receptor agonists, also called incretin mimetics, are a class of medications that copy the action of the natural hormone GLP-1. They bind to GLP-1 receptors in the pancreas, brain, and stomach, triggering insulin release when blood sugar is high, slowing gastric emptying, and reducing appetite (Cleveland Clinic).

What are the brand names?

• Semaglutide – Ozempic (diabetes), Wegovy (obesity), Rybelsus (oral)
• Liraglutide – Victoza (diabetes), Saxenda (obesity)
• Dulaglutide – Trulicity (diabetes)
• Exenatide – Byetta (twice daily), Bydureon (weekly)

The HPRA in Ireland lists all of these as authorised medicines, emphasizing they are prescription-only and must be used under medical supervision (HPRA).

What is the difference between semaglutide and liraglutide?

Semaglutide and liraglutide are both GLP-1 agonists, but they differ in dosing frequency, half-life, and trial outcomes. Semaglutide is administered once weekly (Ozempic, Wegovy), while liraglutide requires daily injections. In head-to-head studies, semaglutide has shown greater weight loss and HbA1c reduction, though both are effective (NCBI Bookshelf). The HSE notes that their side effect profiles are very similar, with nausea, constipation, and diarrhoea affecting both (HSE).

The implication: patients who struggle with daily injections may prefer semaglutide, while those with budget constraints might opt for liraglutide if it’s covered.

Is Ozempic a GLP-1 agonist?

Yes, Ozempic (semaglutide) is a GLP-1 agonist. It is one of the most widely prescribed medications in this class, approved for type 2 diabetes and, under the brand name Wegovy, for obesity. The active ingredient, semaglutide, is a synthetic analogue of the GLP-1 hormone (HPRA).

What is the difference between Ozempic and other GLP-1 agonists?

Ozempic (semaglutide) is distinct from dulaglutide (Trulicity) and liraglutide (Victoza) primarily in its molecular structure and dosing. Semaglutide has a longer half-life, allowing weekly dosing, whereas liraglutide requires daily injections. Dulaglutide is also weekly. In clinical trials, semaglutide has demonstrated superior weight loss compared to dulaglutide and liraglutide (NEJM editorial).

Are GLP-1 and Ozempic the same?

Not exactly. GLP-1 (glucagon-like peptide-1) is a natural hormone produced in the gut. Ozempic is a brand name for a medication that mimics GLP-1’s action. So while Ozempic is a GLP-1 agonist, the term “GLP-1” refers to the hormone itself, not the drug. The full form is “glucagon-like peptide-1” (Diabetes UK).

Who cannot take GLP-1?

GLP-1 agonists are not suitable for everyone. The main contraindications are a personal or family history of medullary thyroid carcinoma (MTC) and multiple endocrine neoplasia syndrome type 2 (MEN2). They are also not recommended for people with severe gastrointestinal disease, such as gastroparesis, because they slow gastric emptying (Cleveland Clinic).

What are the contraindications?

• History of medullary thyroid carcinoma (MTC) or family history of MTC
• Multiple endocrine neoplasia syndrome type 2 (MEN2)
• Severe gastrointestinal disease (e.g., gastroparesis)
• Pregnancy and breastfeeding (limited data, caution advised)

The Irish clinical resource SCHCom advises that patients should have follow-up 3–4 months after starting to assess tolerability (SCHCom).

Who should avoid GLP-1 agonists?

People with a history of pancreatitis, gallbladder disease, or kidney injury should use these drugs with caution. The HSE also warns that hypoglycaemia can occur when GLP-1 agonists are combined with sulphonylureas or insulin (HSE). The HPRA has flagged illegal online sales of semaglutide products, reinforcing that only approved, prescription-only sources are safe (HPRA).

The catch: even with proper oversight, patients with certain conditions may still face elevated risks that require careful monitoring.

What GLP-1 is available in Ireland?

Several GLP-1 agonists are authorised in Ireland. According to the HPRA, the list includes Ozempic and Rybelsus (semaglutide), Trulicity (dulaglutide), Victoza and Saxenda (liraglutide), and Wegovy (semaglutide for obesity) (HPRA). The HSE also provides guidance on obesity medicines, noting that liraglutide and semaglutide are used for weight management under medical supervision (HSE).

Which GLP-1 agonists are approved in Ireland?

• Semaglutide – Ozempic (diabetes), Wegovy (obesity), Rybelsus (oral)
• Liraglutide – Victoza (diabetes), Saxenda (obesity)
• Dulaglutide – Trulicity (diabetes)

Exenatide (Byetta, Bydureon) is also available but less commonly prescribed. All are injectable except Rybelsus, which is an oral tablet.

How to get a prescription in Ireland?

You need a doctor’s prescription. The Irish College of GPs has a patient leaflet explaining that GLP-1 agonists are typically started at a low dose and titrated up to minimise side effects. The leaflet also notes that long-term use is usually required to maintain weight loss (Irish GP patient leaflet).

Why are people stopping Ozempic?

Discontinuation rates are a major concern. The most common side effects — nausea, vomiting, diarrhoea, and constipation — lead many patients to stop. The Irish GP patient leaflet states that these symptoms may cause some people to discontinue treatment (Irish GP patient leaflet).

What are the side effects that lead to discontinuation?

• Gastrointestinal: Nausea (most common, especially at initiation), vomiting, diarrhoea, constipation, heartburn, stomach cramps
• Serious (rare): Pancreatitis, gallbladder disease, kidney injury, thyroid C-cell tumours
• Eye: NAION (very rare, up to 1 in 10,000 users of semaglutide) (Irish Pharmacy Union)

The IPU article notes that nausea is likely at initiation and tends to decrease over time. For those who cannot tolerate the gastrointestinal effects, switching to a different GLP-1 agonist or adjusting the dose may help.

Why are older people quitting GLP-1?

Older adults may be more sensitive to side effects like nausea, fatigue, and hypoglycaemia when combined with other diabetes medications. The HSE warns that hypoglycaemia risk increases when GLP-1 agonists are used with sulphonylureas or insulin (HSE). Additionally, the requirement for daily or weekly injections, cost, and the need for long-term commitment can be barriers for older patients. A Dublin observational study on liraglutide in type 1 diabetes found it was well tolerated and no episodes of hypoglycaemia or DKA occurred in that cohort (Diabetes on the Net).

The implication: patients should only start these drugs if they are prepared for long-term use and have a maintenance strategy.

Comparison of GLP-1 Agonists

Six key drugs, one pattern: they all work by mimicking GLP-1, but dosing, efficacy, and approval differ.

The implication: for patients in Ireland, Ozempic and Trulicity offer once-weekly convenience for diabetes, while Wegovy and Saxenda are the weight-loss options. Liraglutide (Victoza/Saxenda) requires daily dosing, which may affect adherence.

Upsides and downsides

The pattern: the benefits are substantial for those who can tolerate the therapy, but the downsides create significant barriers for many patients.

What’s confirmed and what’s still unclear

Based on the evidence gathered, here is a clear split:

What this means: while the core mechanisms are well-established, the full picture of long-term outcomes is still emerging.

Expert perspectives

“GLP-1 receptor agonists are incretin analogues that promote glucose-mediated insulin release and are used to treat type 2 diabetes and obesity.”

— NEJM editorial

“GLP-1 agonists are a class of medications that mainly help manage blood sugar (glucose) levels in people with Type 2 diabetes.”

— Cleveland Clinic

Summary

GLP-1 agonists have changed the landscape of diabetes and obesity treatment, but they are not a magic bullet. The evidence shows clear benefits in blood sugar control and weight loss, yet gastrointestinal side effects, high costs, and the need for long-term use create real barriers. For Irish patients and prescribers, the choice is clear: weigh the proven efficacy against the tolerability and cost, and plan for a maintenance strategy that extends beyond the prescription.

Frequently asked questions

The catch: proper adherence is critical to avoid gaps in therapy that could lead to weight regain or loss of glycemic control.

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