Week-by-Week Guide to Weight Loss Injections

What to expect from your weight loss treatment

Starting a new medication can be daunting, especially when it’s long-term. This guide aims to provide a clear understanding of what to expect when beginning treatment with either Mounjaro or Wegovy, our two treatment options available from our weight management service.

Remember, everyone's experience is unique, and it's essential to communicate regularly with your pharmacy throughout your journey with regular check-ins to monitor your progress so that they know if you're ready to proceed to high doses.

Woman holding a weight loss injection

Mounjaro: Your Weekly Journey

Week 1:

  • You’ll start on 2.5mg of tirzepatide
  • You might see a sudden weight drop or very little. Either way, week 1 doesn’t determine how much weight you’ll lose moving forward
  • The most common side effects are nausea, diarrhoea, vomiting, or constipation. These are usually mild and should improve as you adjust to the medication
  • Stay hydrated and eat smaller, more frequent meals if needed

Week 2:

  • Side effects may remain the same or start to improve
  • If symptoms are severe or unmanageable, don't hesitate to contact your pharmacist
  • Your appetite will likely decrease noticeably

Weeks 3-4:

  • The effects of Mounjaro may become more apparent as your body gets used to the treatment
  • Most people notice side effects getting better or disappearing altogether
  • Celebrate these improvements – you're making progress!
  • Don’t forget to keep eating, even if you’re not feeling hungry

Weeks 5-8:

  • If you're ready, your dose increases from 2.5mg to 5mg, so some side effects might return
  • Most side effects resolve within a few days to weeks
  • You may experience a bigger change in your appetite and hunger levels, and you may begin to feel healthier overall

Weeks 9-12:

  • Another dose increase from 5mg to 7.5mg may cause temporary side effects
  • Adjust your diet and lifestyle as needed to manage any discomfort
  • You are not required to increase your dosage yet if you don’t want to

Week 13 and beyond:

  • Final dose increase to 10mg may lead to temporary side effects
  • Your body will continue to adjust over time
  • The dose can increase to 12.5mg or possibly 15mg as max dose

Wegovy: Your Weekly Journey

Weeks 1-2:

  • You’ll start on 0.25mg of Wegovy
  • You may experience some initial side effects like nausea, constipation, mild abdominal pain, or diarrhoea
  • Your appetite will likely decrease noticeably
  • Remember, these effects are common as your body adjusts to the medication

Weeks 3-4:

  • You'll likely feel a more consistent sense of fullness
  • Initial side effects may start to subside

Weeks 5-6:

  • You might see weight loss of around 2-4% of your body fat
  • As your dosage increases, some side effects may return temporarily
  • Stay positive – this is a sign the medication is working!

Weeks 7-8:

  • Many people report feeling generally fitter
  • You may notice improved sleep and mental health
  • These positive changes can be very motivating!

Week 9 and beyond:

  • Your dosage may continue to increase every 4 weeks up to 2.4mg
  • Be aware of potential weight loss plateaus – this is normal
  • Focus on maintaining healthy habits for long-term success

Your Weight Loss Journey, Your Way.

Remember, you’ll only increase your dose if it is how you want to proceed, and with agreement from your pharmacist that it is safe. You won’t be forced to increase if you and your pharmacist aren’t happy it’s the right thing for you.  Your journey with Mounjaro or Wegovy is unique to you.

While this guide provides a general overview, your pharmacist will help with any concerns or questions during your initial consultation and regular check-ins. Stay patient and kind to yourself as your body adjusts to these powerful medications.

With time and persistence, you're taking important steps towards improving your health and well-being, such as lowering blood pressure and reducing the risk of certain health conditions, including diabetes and certain cancers.

Lady reading a weight management leaflet at a Rowlands Pharmacy

This page has been reviewed and approved by our in-house experts.


Approved by: Emily Jones
GPhC number: 2221355
Last Reviewed: March 2025

Meet the team

Emily Jones Pharmacist

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