Mounjaro®

How it works

Dual-action GLP-1 + GIP to suppress appetite

Effect

Drives up to 22.5% body weight reduction

From

£154.99

/month

This treatment option is subject to a consultation followed by clinical review.

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What is Mounjaro?

Mounjaro is a prescription weight loss injection containing the active ingredient tirzepatide, manufactured by Eli Lilly. It’s the first “dual-action” weight loss treatment, meaning it works on two gut hormones instead of one — making it more effective than earlier treatments.

Originally developed for type 2 diabetes, Mounjaro was approved by the MHRA in late 2023 specifically for weight management. It’s licensed for adults with a BMI of 30 or above, or 27+ with weight-related health conditions.

In clinical trials, patients using the highest dose of Mounjaro lost an average of 22.5% of their body weight over 72 weeks — making it the most effective weight loss medication currently available.

How effective is Mounjaro?

Mounjaro is the most effective weight loss medication currently available. Large clinical trials (SURMOUNT) have demonstrated significant results across different doses. The findings were as follows:

People taking the highest dose (15mg weekly) lost an average of 22.5% of their body weight over 72 weeks in the SURMOUNT-1 trial.
In head-to-head trials, Mounjaro produced approximately 5% more weight loss than Wegovy at the highest doses, making it the most effective option currently available.
Those on a placebo lost only around 3.1% of their body weight in the same timeframe.

This shows that Mounjaro can lead to significantly more weight loss than diet and exercise alone, and outperforms other available treatments.

Slim man and a heavier man standing back to back, showing different body shapes

How does Mounjaro work?

Mounjaro contains the active ingredient tirzepatide, a dual-action treatment that targets two key hormones involved in appetite and metabolism.

Unlike single-action treatments, Mounjaro works on both GLP-1 and GIP receptors simultaneously. Here’s what that means for you:

GLP-1 activation: Like Wegovy, Mounjaro activates GLP-1 receptors in your brain, reducing appetite and making you feel full after smaller meals.

GIP activation (unique): What makes Mounjaro different is it also activates GIP receptors, enhancing insulin sensitivity, improving fat metabolism, and providing additional appetite suppression.

Improved metabolism: The dual-hormone approach helps your body become more efficient at processing nutrients and burning fat for energy. Some studies suggest Mounjaro may help preserve muscle mass during weight loss.

Supports blood sugar control: Mounjaro improves how your body uses insulin and helps keep blood sugar levels steady, which is why it was originally developed for type 2 diabetes.

Proven results: In large clinical trials, people taking Mounjaro lost up to 22.5% of their body weight over 72 weeks — approximately 5% more than Wegovy — making it the most effective weight loss treatment currently available.

Smiling woman with curly hair in a turquoise vest top exercising outdoors in the sunshine

Who is eligible for Mounjaro?

Mounjaro is designed for people who need extra support with weight management and meet certain medical criteria. If you’ve struggled with weight loss in the past, it may be the most effective option worth exploring.

Here’s what’s involved:

Eligibility: You’ll usually need a BMI of 30 or more, or a BMI of 27+ if you also live with a weight-related condition such as type 2 diabetes, high blood pressure, or sleep apnoea.
Lifestyle support: Mounjaro should be used alongside healthy lifestyle and dietary changes for best results.
When it’s considered: It’s aimed at people who want the most effective weight loss option available, especially those who have tried other methods without lasting success.
Assessment process: To be considered, you’ll first complete an online questionnaire about your health and weight history.
Clinical review: A Trimu clinician will then carefully review your answers, your medical history, and your goals to decide if Mounjaro is the right option for you.

Who shouldn’t use Mounjaro?

Mounjaro isn’t suitable for everyone. It should not be used if you:

Are pregnant, breastfeeding, or planning a pregnancy.
Have had a serious allergic reaction to tirzepatide or any of its ingredients.
Have a personal or family history of medullary thyroid carcinoma (a rare type of thyroid cancer) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2).
Have severe gastrointestinal disease or a history of pancreatitis.
Have severe kidney disease.

Instructions

How to take Mounjaro

Taking Mounjaro is simple. It comes as a pre-filled, single-dose KwikPen that you use once a week on the same day each week, with or without food. Pick your injection day and keep it consistent. Press and hold the pen against your skin for 10 seconds — and that’s it. Store your pen in the fridge (2-8°C), or at room temperature for up to 21 days if needed.

Step-by-step Instructions

Step 1

Prepare your KwikPen

Remove the KwikPen from the fridge and let it reach room temperature. Check the label to make sure you have the correct dose.
Check that the medicine is clear and colourless. Do not use if it looks cloudy, discoloured, or contains particles.
Pull off the grey base cap. You’ll see the needle is already attached — Mounjaro KwikPens are single-use and pre-loaded.

Step 2

Choose your injection site

You can inject Mounjaro into your stomach (at least 2 inches away from your belly button), the front of your thighs, or the upper arm if someone else is helping.
Use a different spot each week to avoid skin irritation.
Clean the area with an alcohol wipe before injecting and make sure the skin isn’t broken or irritated.

Step 3

Inject the medicine

Place the clear base flat against your skin at the injection site.
Unlock by turning the lock ring, then press and hold the purple injection button. You’ll hear a loud click when the injection starts.
Keep the pen in place and slowly count to 10 to ensure the full dose is delivered. You’ll hear a second click when it’s complete.

Step 4

After the injection

Lift the pen away from your skin. The needle will retract automatically into the pen — you won’t need to recap it.
Dispose of the entire used KwikPen safely in a yellow sharps bin. Each pen is single-use only.
Store any unused pens in the fridge (2-8°C). They can be kept at room temperature (up to 30°C) for up to 21 days if needed.

FAQs

Things you should know about Mounjaro

In clinical trials, Mounjaro produced more weight loss than Wegovy (approximately 20-22% vs 15% body weight). This is because Mounjaro works on two hormones (GLP-1 and GIP) rather than just one. However, individual responses vary, and both are highly effective treatments. Your clinician can help you decide which is best for your situation.

In the SURMOUNT-1 trial, participants on the highest dose (15mg) lost an average of 22.5% of their body weight over 72 weeks. For someone weighing 100kg, that’s approximately 22.5kg. Results vary based on starting weight, dose, diet, exercise, and individual factors.

Some people experience temporary hair thinning on Mounjaro. This isn’t a direct drug effect — it’s called telogen effluvium and happens with any rapid weight loss. The body prioritises essential functions during significant weight change. Hair typically regrows once weight stabilises. Ensuring adequate protein intake can help minimise this effect.

If you miss a dose, take it as soon as you remember if it’s within 4 days of your scheduled dose. If more than 4 days have passed, skip the missed dose and take your next dose on your regular scheduled day. Don’t double up doses.

Store Mounjaro in the fridge at 2-8°C. If needed, unused pens can be kept at room temperature (up to 30°C) for up to 21 days. Do not freeze Mounjaro and do not use it if it has been frozen. Keep the pen in its original packaging to protect from light. Mounjaro is delivered in temperature-controlled packaging — store it in your fridge upon arrival.

Like all medications, Mounjaro can cause side effects. The most common include nausea, diarrhoea, constipation, decreased appetite, vomiting, and indigestion. These are usually mild and tend to improve as your body adjusts, particularly during the first few weeks and during dose increases. Less common side effects include abdominal pain, acid reflux, bloating, hair loss, injection site reactions, and fatigue. Rare but serious side effects can include pancreatitis, gallbladder problems, and severe allergic reactions. Seek immediate medical attention for severe stomach pain or signs of allergic reaction.

Yes, switching is possible and some people do switch if they want to try for greater weight loss or if they’re experiencing side effects on Wegovy. Your clinician will advise on the best approach — typically you’d start Mounjaro at the beginning dose (2.5mg) even if you were on a higher Wegovy dose, to let your body adjust to the new medication.

Mounjaro and Zepbound both contain tirzepatide and are made by Eli Lilly. In the US, they’re marketed separately — Mounjaro for diabetes and Zepbound for weight loss. In the UK, Mounjaro is licensed for both indications. They’re essentially the same medication.

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Why you can trust Trimu

Regulated care from a registered UK pharmacy

Safe, discreet treatment — reviewed by qualified clinicians and dispensed by our own UK-registered pharmacy.

Registered UK pharmacy

Dispensed by a GPhC-registered UK pharmacy (premises 1037748).

Reviewed by registered clinicians

GMC-registered doctors and GPhC-registered pharmacists check every case before any treatment is approved.

Discreet, ongoing support

Free, discreet delivery and clinical support throughout your treatment.

Our mission

Trimu began with a simple belief: getting safe, effective treatment shouldn’t be expensive, complicated, or embarrassing. We pair UK-registered clinicians with our own regulated pharmacy to offer honest advice, fair prices, and genuinely discreet care — so you can get on with feeling better.