Choosing between weight loss injections such as Mounjaro, Wegovy and Ozempic can be confusing. Each medicine works in a slightly different way, has its own dosing plan and suits different people. This comparison explains how these injections work, how they are taken, what results to expect, common side effects and safety, and how to decide with a doctor which option fits your goals.
How weight loss injections work: GLP-1 and related medicines
Weight loss injections target appetite and fullness signals. Wegovy and Ozempic contain semaglutide, which mimics the hormone GLP-1. Mounjaro contains tirzepatide, which acts on GLP-1 and a second hormone called GIP. These pathways help you feel satisfied sooner and for longer, and they can reduce day to day hunger. Medicines support lifestyle change, they do not replace it, so nutrition, movement and sleep still matter.
Licences for weight-loss injections and diabetes treatment in Ireland
Wegovy is licensed for weight management alongside reduced calorie intake and increased physical activity. It is used in adults with obesity and in some adults with overweight who have weight related health risks under licence criteria.
Mounjaro is licensed for type 2 diabetes and carries an EU licence for weight management in adults who meet BMI criteria.
Ozempic is licensed for type 2 diabetes and for cardiovascular risk reduction in that population. Ozempic is not licensed for weight management in Ireland.
Your doctor will prescribe a licensed option that fits your medical history.
Dosing and titration: how Mounjaro, Wegovy and Ozempic are taken
All three are taken as once weekly injections under the skin. Treatment usually starts with a low dose that increases step by step to improve tolerance. Slow and steady increases reduce nausea and allow you to find the lowest effective dose.
For our current pricing of weight loss injections in Ireland see Mounjaro and Wegovy. Your doctor can show you how to store, handle and inject safely, including how to rotate injection sites.
- Wegovy, once weekly, starts low then steps up as tolerated.
- Mounjaro, once weekly, uses graduated strengths with reviews at each step.
- Ozempic is also once weekly and is licensed for diabetes care. Weight loss use may be off label and should be guided by a doctor.
Expected results: effectiveness and time frames
Most people notice appetite changes within the first few weeks. Meaningful weight change usually builds over several months as you reach a maintenance dose and settle into routines. Progress is rarely linear. Reviews every four to twelve weeks help you adjust your plan, manage side effects and stay motivated.
Medicines work best alongside supportive habits. Focus on protein with each meal, vegetables and high fibre carbohydrates, regular activity you enjoy and consistent sleep. These habits preserve muscle and make the programme easier to maintain.
Side effects and safety: nausea, constipation and reflux
The most common effects are nausea, constipation, diarrhoea, bloating, reflux and a feeling of fullness. These usually settle over time. Eating smaller portions, slowing your pace and limiting rich foods can help. Hydration and fibre support regular bowel habits.
Seek medical advice urgently if there is severe or persistent stomach pain, repeated vomiting, signs of dehydration or if you feel faint. Do not use weight loss injections if you are pregnant, planning pregnancy or breast feeding. Tell your doctor about all medicines and conditions, including gallbladder disease, pancreatitis and thyroid problems, so they can advise safely for your situation.
See our guides on what to expect week by week for Wegovy and Mounjaro.
Who might suit Wegovy, Mounjaro or Ozempic?
Suitability depends on your medical history, other medicines and your response to early doses. Some people prefer the simplicity of one pen system, others value flexibility over dose sizes. Discuss personal priorities such as appetite control, side effect pattern and your weekly routine.
- Mounjaro may suit people who need robust appetite control and who are comfortable with stepwise dose increases.
- Wegovy may suit people who prefer a GLP-1 only medicine with clear weekly dosing and established weight management use.
- Ozempic is licensed for type 2 diabetes. Any weight loss use should be directed by a doctor who knows your history.
Costs, supply and practical access
To understand costs, you can see our prices for Mounjaro and Wegovy. Prices depend on dose and brand. Budget for ongoing treatment and plan refills early to avoid gaps.
Supply can vary. Order ahead of time and keep your prescription details to hand. Store pens in line with the patient leaflet and ask your pharmacist about travel storage if you fly or commute often.
Making weight loss injections work in real life
Plan regular meals with protein, vegetables and high fibre carbohydrates. Keep snacks simple and portioned. Many people find it helpful to reduce very rich or greasy foods while settling into treatment.
Build a weekly movement plan that you can keep over time. Brisk walking, short strength sessions and stretching support energy and protect muscle. Sleep routines and stress management, such as short breathing exercises, also help.
- Eat slowly and stop when comfortably full.
- Drink water regularly, especially on dose increase weeks.
- Keep a simple note of dose dates, side effects and wins you notice.
Reviews and monitoring with your doctor and pharmacist
Schedule reviews to check weight, waist, blood pressure and any medicine interactions. Bring a list of medicines and supplements to each appointment. A pharmacist can help with injection technique and side effect plans. A doctor will decide when to pause, reduce or increase doses, and when to switch products if needed.
If you are using an online assessment, complete the questionnaire honestly and include full medical history. Clear information helps your prescriber choose a safe and effective plan.
Start with a convenient online assessment
If you are looking to get prescribed, visit our online doctor partner, Zava, who will assess if treatment is suitable for you.
Supports available in Ireland
- HSE, medicines and surgery for obesity
- HSE, obesity treatment overview
- HPRA, find an authorised medicine
FAQs
Which weight loss injection works fastest?
Early appetite changes are common within weeks. Lasting results build over months with steady titration and supportive habits.
Can I drink alcohol while using weight loss injections?
Moderation is safest. Alcohol can worsen reflux and nausea, so plan small amounts and avoid on dose increase days.
Do I need to diet while on injections?
Balanced eating supports results. Aim for protein, vegetables and whole grains. Strict diets are rarely needed and can be hard to maintain.
What if side effects are hard to manage?
Speak to a doctor or pharmacist. Slowing titration, adjusting meal size and timing and hydration usually help.
Are these injections safe in pregnancy?
No. Do not use during pregnancy or breast feeding. Discuss plans with your doctor before trying to conceive.
If you have questions about choosing or using weight loss injections, our team is here to help. Contact us for friendly, confidential advice.
