Starting Your Weight Loss Journey - 2.5mg

If you’re reading this, it’s likely your first dose of Mounjaro has just arrived or will be with you soon. This marks the beginning of your treatment, and we’ll guide you through everything you need to know as you get started.

Three key takeaways

• The 2.5mg starter dose is designed to help your body adjust gently while you learn how treatment works and see how your body responds.
• Early side effects like nausea or acid reflux can be common, but they're usually mild and tend to settle as your body adapts.
• Building healthy habits around food, movement, and setting new routines can help you get the most from treatment in your first few weeks.

1. Double check your order

When your parcel arrives, the first thing to do is open it and make sure everything is there and in good condition. Confirm that:

• your pens feel cold (not frozen or warm)
• the packaging is intact
• the correct strength and quantity have been delivered

If anything does not look right or something is missing, reach out to our team so we can help put it right as quickly as possible.

What’s in the box

It’s a good idea to familiarise yourself with what’s inside your delivery so you know exactly where everything is when you need it. Your delivery will include:

• Mounjaro 2.5mg pens
• single-use needles
• alcohol swabs
• instructions for use and storage

Tip: a sharps bin for used needles isn’t included, so make sure you have one ready before taking your first dose.

Temperature and safety checks

It’s important to check that your Mounjaro has arrived at the right temperature. We carefully pack it in temperature-controlled packaging so it stays cool on its way to you, but taking a quick look when it arrives can give you extra peace of mind.

Mounjaro needs to be stored between 2°C and 8°C, so once it’s delivered, pop it straight into the fridge. A middle shelf or the fridge door is a good choice, as placing it too close to the back can increase the chance of it freezing. Keeping it stored correctly helps make sure your treatment is ready to work exactly as it should.

If you’d like a full breakdown of how to store your pens, see our guide to keeping your Wegovy or Mounjaro pen refrigerated.

Read the leaflet before you start

Your patient information leaflet explains:

• how to inject your first dose
• recommended injection sites (you can also read our guide on the best place to inject Mounjaro)
• common early side effects
• how to store, handle, and dispose of the pen

2. Get ready to inject your first dose

Taking your first injection is a big step, and it’s completely understandable to feel a bit nervous. Giving yourself a little time to prepare can help you feel more confident before getting started.

Always follow the step-by-step instructions in your patient leaflet and use our guide on how to take Mounjaro for clear, practical support. Knowing the steps ahead of time can make the process feel much more familiar and easy to manage.

Before you inject, choose a time when you're not rushed and a space where you feel comfortable. Have everything you need within reach, wash your hands, and take a moment to go through each step. There is no need to hurry.

Remember: most people are surprised by how quick and straightforward the injection is once they’ve done it. And after the first one, it often just becomes part of your weekly routine.

If you feel unsure at any point, you can pause and reach out to our clinical team for reassurance. We’re here to help you start with confidence.

General safety questions

• Bubbles in the pen? Small air bubbles are normal.
• Cloudy or discoloured liquid? Do not use the pen. Contact customer care.
• Pen left out of the fridge? Check our storage safety guide or speak to a pharmacist.
• Warm pen on arrival? Refrigerate it and contact customer care.
• How to dispose of the pen and needle? Use a sharps bin, then follow your local disposal guidance.

3. Learn how to deal with side effects

Early side effects like nausea, indigestion, constipation, or diarrhoea can happen when starting Mounjaro, but for most people, they are mild and tend to ease as the body adjusts. Not everyone experiences side effects, but knowing what’s possible and how to manage them can help you feel more prepared.

Common early side effects include:

• nausea
• constipation
• diarrhoea
• acid reflux or heartburn
• reduced appetite
• bloating or mild stomach discomfort

Most of these improve with time, especially as your body gets used to treatment. Eating smaller meals, staying hydrated, and listening to your hunger cues can make a real difference in those early weeks.

For a full overview of side effects, see our Mounjaro side effects guide.

Tips for managing common side effects:

Nausea

Nausea is the most common early side effect and often improves after your first few injections. Helpful tips include:

• eating smaller meals
• avoiding large or high-fat foods
• staying upright after eating
• drinking regularly in small sips

Constipation

Constipation can occur as your digestive system adapts. It usually goes away quickly and can often be managed with:

• gentle movement
• fibre-rich foods
• staying hydrated
• simple over-the-counter treatments if suitable

Diarrhoea

Diarrhoea can be fairly common when starting treatment, but you can deal with it by:

• Eating small, bland meals
• Staying hydrated to replace lost fluids
• Over-the-counter (OTC) anti-diarrhoea treatments

For more advice, visit our diarrhoea & constipation on Mounjaro guide.

Heartburn and acid reflux

Reflux or indigestion can develop from day 1. Simple changes can help, such as:

• avoiding spicy or acidic foods
• eating smaller meals
• not lying down after eating
• limiting caffeine or fizzy drinks

More support is available in our Mounjaro heartburn guide.

Listen to your body

As your body adjusts to treatment, side effects often begin to settle. But if they're ongoing or starting to impact your daily life, it’s important to speak to a clinician. You do not have to push through discomfort on your own.

You may also want to remain on 2.5mg for a little longer to give your body more time to adapt. There is no need to rush. Moving at a pace that feels manageable helps set you up for a more comfortable journey.

When to seek medical attention

Serious side effects are rare, but you should know when to get help if needed. Seek immediate medical advice if you experience:

• severe vomiting or inability to keep fluids down
• ongoing diarrhoea leading to dehydration
• chest pain or persistent severe reflux
• symptoms that worsen instead of improving

If you’re unsure whether your symptoms are normal, contact a pharmacist, clinician, or NHS 111.

4. Build new, healthy habits

Simple, healthy habits make your first few weeks on Mounjaro easier and help you get the most from treatment. Focus on gentle changes to your daily routine, including food choices, movement, hydration, sleep, and tracking your progress in a way that feels manageable.

Start with small dietary changes

You do not need a strict plan. Instead, focus on building a routine that works with your changing appetite and energy levels.

• Regular mealtimes can help prevent you from becoming overly hungry, which often makes food choices harder. Even if your appetite is lower, try not to skip meals completely.
• Smaller portions are often more comfortable, especially in the early weeks. You can always have more if you need it, but starting smaller reduces the risk of nausea or discomfort.
• Lighter meals on injection days may feel better for your stomach. Many people prefer simple, balanced foods that are easier to digest rather than heavy or high-fat meals.
• Staying hydrated is key. Sip water regularly throughout the day rather than drinking large amounts at once, and keep fluids up if your appetite is reduced. Good hydration can also help with common side effects like headaches or constipation.

If you want to learn more, visit our Mounjaro diet plan.

Begin introducing movement

Moving more is essential to getting the most out of your treatment. This doesn't mean running to the gym or doing anything extreme. You can keep things simple by making a few changes to your regular habits.

Try starting with:

• Short walks, especially after meals to support digestion, help regulate blood sugar, and gently build towards more activity without putting too much pressure on your body.
• Stretching or mobility exercises to reduce stiffness, improve flexibility, and help your body feel looser and more comfortable as it adjusts to treatment. These can be as simple as a 5–10 minute routine at home.
• Light household activities like tidying, gardening, or even standing while doing work. These everyday movements add up and are a great way to ease into being more active without needing a structured workout.

Learn more about getting into the mindset of exercise.

Support your nutrition

Alongside balanced meals, some people like to use supplements to support general health. If you’re considering vitamins, our Mounjaro supplements guide explains what may be useful and when to speak to a clinician.

Track your progress

Keeping track of your weight, routine, or goals can help you stay focused and motivated, while also reminding you how much progress you’re making.

You do not need a complicated system. A simple app, notes on your phone, or a small journal works perfectly. What matters is finding something you’ll stick with.

You might choose to track:

• Your weight once per week, on the same day and at a similar time
• How your appetite is changing
• Your movement or step count
• Meals or protein intake
• Side effects and how you’re managing them
• Energy levels, sleep, or mood
• Small wins, like making healthier choices or feeling more in control around food

A helpful reminder: try not to weigh yourself too often. Daily fluctuations are completely normal and can be influenced by things like hydration, hormones, or salt intake. Weighing once a week usually gives a clearer, more encouraging picture of your progress.

5. Think about what realistic progress looks like

It’s important to know what to realistically expect from 2.5mg of Mounjaro, so you don’t feel discouraged early on. This first dose is used to help your body adjust to the medication, not to drive rapid weight loss straight away.

Some people notice changes in appetite or food cravings before they see changes on the scales, while others may not notice much in the first few weeks. Weight loss with Mounjaro is rarely a straight line, and small or steady changes early on do not mean your treatment isn't working.

Early progress often shows up in other ways, like feeling satisfied with smaller portions, thinking about food less often, or finding it easier to stop eating when you’re full.

Track your progress beyond the scales

The number on the scales is only one way to measure your progress, and it doesn’t always tell the full story, especially early on.

Other signs of progress include looser clothes, higher energy levels, reduced appetite, or simply feeling more in control around food. Noticing these changes can help you stay motivated even when the scales don’t move as quickly as you expected (or want them to!)

6. Ask for help if you need it

Starting any new treatment means questions, even if everything is going well. You don’t need to wait until something feels “serious” to reach out for help.

You may want to speak to one of our pharmacists or your doctor if:

• side effects feel persistent or are affecting daily life
• you’re unsure about injection timing or missed doses
• you’re worried you’re not eating enough
• you feel anxious about your progress or expectations

Support is there to help you feel safe and confident throughout your treatment. Asking questions early can prevent small concerns from becoming bigger worries.

7. Know when and how to increase your dose

Most people move from 2.5mg to 5mg after four weeks, provided they are tolerating treatment well and any side effects feel manageable. This gradual increase is designed to help your body adjust comfortably while supporting steady progress.

As your next dose approaches, we’ll be in touch to check how you’re getting on and guide you through the process. For some people, staying on their current dose a little longer may be recommended, and that is completely okay too.

Always follow your clinician’s advice before making any changes to your dose. Your treatment plan is tailored to you, and adjusting it safely is one of the most important ways to protect both your progress and your wellbeing.

Learn more about when to increase your dose.

8. Order treatment in advance

We recommend placing your next order at least two weeks before your current order runs out. This means you've got plenty of time for your next order to arrive to avoid any interruptions to your treatment.

Make it a bundle if you’re tolerating treatment well

If you’re ready to move to 5mg, you can order a bundle for the next part of your treatment. This helps you stay stocked and reduces the risk of missing a dose.

Frequently asked questions about Mounjaro 2.5mg

How do I dispose of the sharps bin?

Return your full sharps bin using your local council’s collection or drop-off service. Do not place it in household waste.

Can I keep my pen out of the fridge?

Your pen can stay at room temperature (below 30°C) for up to 21 days. Once kept out, do not return it to the fridge.

The liquid is cloudy, is it safe to use?

No. The liquid should be clear, slightly yellow or colourless. If it looks cloudy or abnormal, do not use it.

There are bubbles in my pen, is this safe to use?

Yes. Small air bubbles are normal and do not affect your injection.

How do I reorder the pen? I need some help deciding which dose to order next.

Reorder through your Chemist4U account. If you’re unsure which dose is next, use our Mounjaro dosing schedule or speak to a clinician.

What if I have injected in the wrong place?

If you injected into the wrong area but still used one of the approved sites, continue as normal. If you’re unsure, contact a clinician for advice.

When will I start to see results?

Some people notice changes in appetite within the first few weeks. However, weight changes vary from person to person, it can take longer.

Sources

Mounjaro KwikPen 2.5mg solution for injection in pre-filled pen (2025) EMC [accessed 17 November 2025]

Tirzepatide for managing overweight and obesity (2025) NICE [accessed 17 November 2025]