What to Expect During Your First Month on Mounjaro

If you're considering Mounjaro (tirzepatide) for weight loss, you're not alone. This new generation injectable has been approved in the UK for weight management in people with obesity or those with weight-related health conditions. But what is it really like during the first month on Mounjaro?

At Happy Pharmacy, we understand that starting a new treatment can bring questions and concerns — especially when it involves injections. That’s why we offer a trusted online consultation, guidance from healthcare professionals, and ongoing support throughout your treatment.

In this blog, we’ll walk you through what to expect during the first 4 weeks on Mounjaro, from dosage to side effects, results, and tips for staying on track.

What Is Mounjaro?

Mounjaro is a once-weekly injectable medication containing tirzepatide, a dual GLP-1 and GIP receptor agonist. It works by:

• Regulating blood sugar levels

• Slowing gastric emptying

• Reducing appetite and cravings

• Promoting a feeling of fullness

Originally developed to treat type 2 diabetes, Mounjaro has also been approved by the MHRA for weight management in the UK under specific guidelines. It’s available online through regulated pharmacies like Happy Pharmacy, following a simple, safe online consultation.

Week-by-Week: What to Expect in Month One

Let’s break down the first month of your Mounjaro journey.

Week 1: Starting the Journey

Dosage: You will usually begin with the lowest dose, typically 2.5 mg once a week. This starting dose is designed to help your body adjust to the medication and minimise side effects so your weight loss journey can be safely personalised going forward.

What you may notice:

• Reduced appetite and portion sizes

• Early signs of satiety (feeling full faster)

• Mild nausea or stomach discomfortSupport tip from Happy Pharmacy:

Drink plenty of water, eat slowly, and avoid greasy foods in your first week. Our team is available for guidance if side effects are troublesome or you have questions.

Week 2: Settling In

By week 2, your body is beginning to adapt. Most users report a noticeable change in eating habits, including:

• Fewer cravings, especially for high-calorie snacks

• Less emotional or mindless eating

• Greater awareness of portion control

Common mild side effects:

• Nausea

• Constipation

• Bloating or burping

These effects usually ease after a few days. It's your body's natural response to Mounjaro’s action on the digestive system.

Safety advice:
If symptoms persist or become severe, contact Happy Pharmacy's support team or your GP. All Mounjaro prescriptions from Happy Pharmacy come with access to advice from UK-registered healthcare professionals.

Week 3: Building Momentum

By now, many users feel more comfortable with the injections and may notice the beginning of weight loss. While individual results vary, some people experience:

• Noticeable weight loss

• More energy due to reduced overeating

• Fewer blood sugar fluctuations (especially for those with insulin resistance)

At this stage, the goal is consistency. Keep taking Mounjaro on the same day each week, and combine it with:

• A balanced, reduced-calorie diet

• Light physical activity including weights

• Regular hydration

Did you know?
Studies show that Mounjaro users who follow a structured lifestyle plan alongside their treatment tend to see greater weight loss than those who don’t.

Week 4: Preparing for the Next Step

After completing four weeks on the 2.5 mg dose, the dosage may increase to 5 mg unless side effects are still present. This step-up helps maximise the benefits of tirzepatide for long-term weight loss.

What to expect with the increase:

• Renewed appetite suppression

• Possible return of mild side effects as your body adjusts

• Enhanced satiety and more consistent weight reduction

This is a good time to check in with your progress. At Happy Pharmacy, our processes ensure periodic reviews and check-ins to ensure you’re responding well and to offer additional support if needed.

Managing Common Side Effects

Mounjaro is generally well tolerated, but like all medications, it can cause side effects  especially in the first month.

Most common side effects:

• Nausea

• Diarrhoea or constipation

• Bloating

• Loss of appetite

• Headache

These are usually short-lived and manageable with lifestyle changes.

Tips for relief:

• Eat small, frequent meals

• Avoid high-fat, spicy, or sugary foods

• Stay hydrated with water or herbal teas

• Rest if you feel tired or dizzy

If any side effects become severe or don’t go away, consult a healthcare professional. Happy Pharmacy provides trusted aftercare for all patients using Mounjaro.

How Much Weight Can You Lose in Month One?

Weight loss varies depending on your diet, activity levels, and metabolism. In clinical trials, many patients lost 2–5% of their starting body weight within the first 4–8 weeks.

Average loss:

• 1 to 4 kg (2 to 9 lbs) in the first month

• Results improve with higher doses and long-term use

But remember — the goal is sustainable, long-term weight management. Don’t be discouraged if your first month is focused more on side effect management than dramatic weight changes. It’s the start of a personal, sustainable journey.

Is Mounjaro Safe?

Yes — Mounjaro is MHRA-approved and considered safe when prescribed appropriately. At Happy Pharmacy, we follow strict GPhC guidelines to ensure patient safety.

Safety considerations:

• Mounjaro is not suitable during pregnancy or breastfeeding

• It may interact with medication, always list everything you are taking so we can ensure it is safe for you to take it

• People with a history of pancreatitis should not use it

That’s why it’s essential to complete a full online consultation before starting, and to keep your prescriber updated about any health changes.

What Makes Happy Pharmacy a Trusted Source?

When it comes to ordering weight loss medication online, regulation and trust matter. Happy Pharmacy is a UK-based, GPhC-registered online pharmacy, offering:

✅ Licensed UK prescribers
✅ Free online consultations
✅ Secure and discreet delivery
✅ Ongoing clinical support
✅ Transparent pricing — no hidden fees

You’ll never be left wondering what to do next, we guide you at every step of your weight loss journey.

Tips to Succeed During Your First Month

1. Be consistent – Take your injection the same day each week.

2. Listen to your body – Eat when hungry, stop when full.

3. Log your symptoms and progress – This helps your prescriber tailor your care.

4. Stay hydrated – Helps ease side effects like nausea and constipation.

5. Ask for help – Our team is always here to support you.

Looking Ahead: What Happens After Month One?

After completing your first month on the 2.5 mg dose, your prescriber may increase your dosage to 5 mg. If well tolerated, this will continue for another month or more.

Over time, your doses may be gradually increased further but this will be based on your personal journey, progress and check-ins with our qualified team.

Most users experience their most significant weight loss between months 2 and 6, particularly when they pair medication with healthy eating and regular exercise.

Final Thoughts: Trust the Process, Trust Happy Pharmacy

Starting Mounjaro for weight loss can feel like a big step but it’s one that thousands of people across the UK are taking with confidence.

Your first month is about building the foundation: getting used to the medication, managing side effects, and starting your journey toward better health. With the right guidance and support, Mounjaro can help you reach meaningful, lasting results.

At Happy Pharmacy, we’re here to provide a safe, regulated, and trusted service from online consultation to prescription and delivery. Whether it’s your first week or your fiftieth, you’ll never be alone on your journey.

Ready to Start Your Mounjaro Journey?

Take your first step today with a simple online consultation. Our expert team will assess your eligibility, provide guidance, and support you every step of the way.

👉 Visit our Weight Loss Consultation page to get started.

Blog medically reviewed by : Nigel Howard, GPhC Registered Prescriber, 4 June 2025

References

1. NHS – Weight loss medicines

2. NICE – Tirzepatide for managing overweight and obesity

3. New England Journal of Medicine – Tirzepatide and Weight Loss

4. MHRA – Medicines and Healthcare products Regulatory Agency