Mounjaro

• Active ingredient: tirzepatide
• Format: Pre-filled Mounjaro pen for weekly weight loss injections
• Strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg, 15mg
• Review: A healthcare professional checks your assessment before supply
• Support: Guidance is available throughout your weight loss journey
• More detail: Read the patient information leaflet before starting Mounjaro
• Monitoring: Mounjaro is under additional safety monitoring in the UK

Mounjaro is a dual agonist weekly weight loss injection containing tirzepatide, which works through two hormone pathways - GIP and GLP-1. That dual action helps you feel fuller for longer, reduces appetite, and has delivered strong results in clinical trials.

In SURMOUNT-1, average weight loss reached 22.5% over 72 weeks maintaining a 15 mg dose.

In the SURMOUNT-5 trial, tirzepatide also delivered stronger average weight loss than semaglutide (Wegovy/Ozempic).

Mounjaro works through two hormone pathways - glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) - that signal to your brain that you are full. Most weight loss injections work on one pathway. Mounjaro works on both.

In practical terms this means:

• Reduced appetite: you feel less driven to eat between meals
• Less food noise: cravings become easier to manage
• Feeling fuller for longer: meals feel more satisfying, even smaller ones
• Steadier blood sugar: fewer hunger spikes throughout the day

Mounjaro works best alongside healthy eating and regular physical activity, with ongoing support from your clinical team.

Mounjaro starts working from your first dose. Most people notice a reduction in appetite and cravings within the first week. Visible changes to your weight tend to follow over the coming months, and results continue to build throughout treatment. Noticeable changes become more apparent at around month 3.

Weight loss is not always reflected immediately on the scales. How your clothes fit and how you feel are equally - if not more - useful measures of progress. Everyone responds slightly differently, and your prescriber will monitor your progress and adjust your dose when needed.

Mounjaro supports weight management alongside healthy eating and regular physical activity. Each treatment has its own clinical profile, and the right choice depends on your individual circumstances. A thorough assessment is the best way to find the treatment that suits you.

Other prescription weight loss injections are available in the UK, including Saxenda, Wegovy, and Nevolat.

Mounjaro is licensed for adults living with obesity with a BMI of 30 or above, and for overweight adults with a BMI of 27 to 30 who have a weight-related medical condition, such as:

• High blood pressure
• High cholesterol
• Cardiovascular disease
• Prediabetes
• Obstructive sleep apnoea

There is a reduced BMI threshold for individuals from South Asian, Chinese, other Asian, Middle Eastern, Black African, or African-Caribbean backgrounds due to higher health risks associated with weight. You can read Mounjaro reviews from UK patients who have used this treatment through our service.

This medication is not suitable for everyone.

You should not use it if you are:

• Under 18 or over 85
• Pregnant or breastfeeding
• Allergic to any of its ingredients

You may also be unable to use it if you:

• Have severe kidney or liver problems
• Have a history of pancreatitis or gallstones
• Have severe gastrointestinal disease
• Currently take other medications that lower blood sugar levels

If any of these apply to you, please discuss your options with a healthcare professional before starting treatment.

Most people achieve 15-20% weight loss within the first year, with some reaching ~20-25% over 1.5-2 years on higher doses. Long-term data shows an average maximum weight loss of around 23% over 3 years, with most people maintaining these results while staying on treatment.

Clinical trial results support this. In SURMOUNT-1, average weight loss over 72 weeks reached:

• 16.0% at 5mg
• 21.4% at 10mg
• 22.5% at 15mg

In the head-to-head SURMOUNT-5 trial, Mounjaro delivered 20.2% mean weight loss compared with 13.7% for semaglutide - roughly 47% more relative weight loss.

Body composition

Most weight lost with Mounjaro comes from fat mass rather than lean mass - roughly three quarters from fat and one quarter from lean tissue. That said, it is important to actively maintain muscle through regular physical activity. This supports healthier body composition changes alongside weight loss.

Clinical data also suggests Mounjaro can support cardiovascular and metabolic health, including reduced risk of heart-failure-related outcomes in people with type 2 diabetes and established cardiovascular disease.

Mounjaro treatment starts at 2.5mg once a week, increasing gradually every 4 weeks until you reach the dose that works best for you. Not everyone needs the highest dose - the goal is the lowest effective dose of Mounjaro for your individual response.

The standard titration schedule is:

Your prescriber will increase your dose in 2.5mg steps every 4 weeks, only when needed. Each dose increase is guided by how you are responding to treatment.

For a full breakdown of how dosing works and what to expect at each stage, read our Mounjaro dosage and maintenance guide.

If you miss a dose of Mounjaro, what you do next depends on how much time has passed:

• Within 4 days of your missed dose - take it as soon as possible
• More than 4 days have passed - skip the missed dose entirely
• Take your next dose on your usual day
• Never take a double dose

Use the Mounjaro weight loss injection once a week, on the same day each week where possible. You can take Mounjaro at any time of day.

Recommended injection sites are:

• abdomen, at least 5cm from the navel
• upper thigh
• upper arm

Rotate injection sites each week. Most patients find the Mounjaro weight loss injection straightforward once they understand the steps. Your prescriber or pharmacist can walk you through use before treatment starts, and injections usually become easier with practice.

1. Wash your hands with soap and water to ensure cleanliness.
2. Inspect the pen before use:
   • Check the expiration date
   • Look for any visible damage
   • Verify the medication appears clear and colourless
3. Attach a new needle to the pen, ensuring it's firmly secured.
4. Prime the pen:
   • Turn the dose knob slowly until you hear 2 clicks
   • Point the needle upward
   • Press the dose knob to release any air bubbles and confirm the pen is working
5. Set your dose:
   • Turn the dose knob to your prescribed dosage (typically starting at 2.5 mg, increasing as directed by your healthcare provider)
   • Listen for clicks to confirm the correct dose is selected
6. Choose and prepare the injection site:
   • Common sites: abdomen, thigh, or upper arm
   • Rotate sites to avoid irritation
   • Pinch the skin gently if preferred
7. Inject the medication:
   • Insert the needle at a 90-degree angle into the skin
   • Press down the dose knob firmly
   • Count slowly to 5 while keeping the needle in place
8. Withdraw and verify:
   • Pull the needle straight out of the skin
   • Check that the dose counter returns to 0
   • Apply gentle pressure with a tissue if needed
9. Secure the pen:
   • Remove the needle from the pen and place in sharps bin
   • Replace the pen cap
   • Store the pen as directed (typically in the refrigerator)

The most common side effects of Mounjaro are:

• Nausea
• Diarrhoea
• Vomiting
• Constipation
• Indigestion
• Stomach pain
• Bloating
• Burping
• Flatulence
• Headaches

These are most noticeable during the first few weeks and after each dose increase. Starting on a low dose and increasing gradually helps reduce their impact.

• Dizziness
• Low blood pressure
• Fatigue
• Injection site reactions
• Rash
• Hair loss - usually temporary and more closely related to rapid weight loss than to the medication itself

Persistent nausea, vomiting, or diarrhoea can lead to dehydration. In some cases this can affect kidney function, including in people with no prior kidney problems. Stay well hydrated throughout treatment and tell your prescriber if symptoms are severe or prolonged.

• Gallbladder problems - including gallstones and gallbladder inflammation
• Acute pancreatitis - seek urgent help if you have severe abdominal pain with vomiting
• Increased heart rate
• Altered taste
• Menstrual changes - some people have reported changes to their cycle or unexpected bleeding. Speak to your prescriber if this occurs

Three-year data from SURMOUNT-1 shows no new safety signals beyond those seen at 72 weeks. Side effects follow the same pattern - mostly digestive, mostly early in treatment.

For a full breakdown of side effects and how to manage them, read our Mounjaro side effects guide.

If you experience any of the following, stop taking Mounjaro and seek medical help immediately:

• Severe stomach pain that spreads to your back
• Persistent vomiting
• Severe upper abdominal pain with fever
• Signs of a serious allergic reaction

Call 999 or go to A&E if symptoms are severe, sudden, or you feel your life may be at risk.

Not sure how urgent your symptoms are?

• Call 111 (or NHS 24 if you are in Scotland) - for urgent symptoms that are not life threatening. A trained adviser will assess your symptoms and direct you to the right care

Do not wait for your next scheduled appointment if you are concerned. When in doubt, call 111 first and they will advise whether you need emergency care.

Mounjaro is under additional safety monitoring in the UK. This means it is a newer medicine and the MHRA is collecting more data on its long-term effects. It does not mean it is unsafe - it means it is being watched closely.

Do not use Mounjaro if you:

• Are allergic to tirzepatide or any ingredient in the Mounjaro pen
• Have a personal or family history of medullary thyroid carcinoma
• Have Multiple Endocrine Neoplasia syndrome type 2
• Are pregnant or breastfeeding

Speak to your prescriber before starting Mounjaro if you have:

• A history of pancreatitis
• Severe gastrointestinal disease
• Kidney problems
• Diabetic retinopathy

If any of these apply to you, your prescriber will assess whether Mounjaro is appropriate or whether an alternative treatment is more suitable. If you experience a side effect, you can report it directly to the MHRA through the Yellow Card scheme. This helps build a clearer picture of how the medicine performs in real-world use.

Mounjaro can interact with some medicines and supplements. Delayed stomach emptying can affect how some medicines are absorbed, and some combinations can increase risk.

• Oral contraceptive pills: Mounjaro slows stomach emptying, which can reduce how much of the pill is absorbed, making it less effective at preventing pregnancy.
• Insulin, sulfonylureas and meglitinides all lower blood sugar. When combined with GLP-1 medication, they increase the risk of hypoglycaemia (blood sugar dropping too low).
• Other GLP-1 medicines: Using more than one GLP-1 receptor agonist is not recommended. This can increase side effect risk without providing additional clinical benefit.
• Oral HRT (hormone replacement therapy): Mounjaro may reduce absorption of the progesterone component of oral HRT. Progesterone helps protect the lining of the womb (endometrium) when used with oestrogen, so reduced absorption could lower this protection. A transdermal option (patch or gel) may be more appropriate as it bypasses the digestive system.
• Supplements (ginseng, chromium): both can affect blood sugar independently, creating unpredictable combined effects.
• Alcohol: can affect blood sugar and increase the risk of side effects including nausea and dizziness.

Mounjaro (tirzepatide) slows stomach emptying, which may affect how some oral medicines are absorbed. This is usually not clinically significant, but for medicines requiring stable blood levels (such as warfarin or lithium), closer monitoring may be needed when starting or adjusting treatment. If unsure of potential interactions with your current medication, speak to your doctor or one of our healthcare professionals before starting treatment.

If you take the oral contraceptive pill, you will need to use additional contraception when starting Mounjaro and after each dose increase. Mounjaro slows stomach emptying, which can reduce how much of the pill is absorbed and make it less effective.

To maintain reliable contraception, use a barrier method or switch to a non-oral contraceptive for 4 weeks after starting treatment and for 4 weeks after each dose increase.

Non-oral methods that are not affected in the same way include:

• The coil
• Implant
• Injection
• Patch
• Vaginal ring

As you lose weight, fertility can increase. Reliable contraception is important throughout treatment. If the contraceptive pill is your preferred method and you do not want to change it, it is worth discussing Wegovy and the contraceptive pill with your prescriber, as it does not carry the same interaction.

Store unopened Mounjaro pens in the fridge at 2 to 8°C. Keep the pen in the original carton and do not freeze it.

Once opened, your Mounjaro pen can be stored below 30°C for up to 30 days - it does not need to go back in the fridge between uses.

Mounjaro is a cold chain medication and must be kept at controlled temperatures during transit. We ship your pen in validated temperature-controlled packaging with ice packs to maintain fridge-safe conditions for at least 48 hours.

Our temperature mapping confirms that even if the ice packs have melted on arrival, your medication has remained within the required temperature range throughout delivery.

If you are not home when your order arrives, we will attempt redelivery. If you have selected a Safeplace, your order will be left there provided the location is safe and suitable. Our packaging keeps your medication within safe temperature conditions for at least 48 hours, so a missed first delivery does not affect the quality of your medication.

Yes. Keep it stored properly using an insulated travel bag with cool packs, and carry it in your hand luggage.

Yes, Mounjaro (tirzepatide) does not cause physical withdrawal, so it is medically possible to stop without gradually reducing your dose. The medication leaves your system over a few weeks and there is no evidence that stopping suddenly causes direct harm.

As Mounjaro leaves your system, appetite and food cravings commonly return toward pre-treatment levels. For many people, some or all of the weight lost during treatment returns - how you stop and consistency of healthy habits have a direct effect on the rate of weight regain. Some of the benefits for blood pressure and cholesterol can also lessen.

• Discuss timing with your prescriber: options may include stepping down to a maintenance dose first, or adjusting other medications if relevant
• Increase focus: on diet and physical activity in the months after stopping
• Consider: behavioural or psychological support to help manage appetite and maintain healthy habits long term

Weight regain after stopping is not a sign that treatment failed - it reflects how the medication works. For many people, ongoing treatment is the most effective way to maintain results.

You can restart on the same dose as your last injection, or move to the next dose up if you tolerated your previous dose well and want to continue progressing.

You may need to restart at 2.5mg and re-titrate from the beginning depending on the strength last used. This gives your body time to readjust and reduces the risk of side effects. If you are unsure which dose to restart on, speak to your prescriber before placing your next order.

Leave one week between your last Wegovy dose and your first Mounjaro dose. You must start Mounjaro at 2.5mg and retitrate gradually, regardless of the Wegovy dose you were on. During the washout period you may feel hungrier than usual - this is normal as your body adjusts.

Leave one week between your last Mounjaro dose and your first Wegovy dose. Depending on your current Mounjaro dose, you may not need to start Wegovy at the lowest dose - your prescriber will advise the most appropriate starting point.

For full guidance on both switching routes, read our dedicated articles:

• Switching from Mounjaro to Wegovy
• Switching from Wegovy to Mounjaro

Injectable treatments work by reducing appetite and slowing digestion. Mounjaro's dual GIP and GLP-1 action sets it apart from other injectable options, which is reflected in its trial data. But stronger average results do not always mean the right fit for every patient.

• Wegovy - semaglutide, once weekly. Strong clinical trial results and one of the most widely used weight loss injections in the UK
• Saxenda - liraglutide, once daily. A proven treatment with a longer track record, suited to patients who prefer a more gradual approach
• Nevolat - liraglutide, once daily. The same active ingredient as Saxenda at a more accessible price point

For patients who prefer not to inject, weight loss pills offer an alternative route. Orlistat is currently the main licensed weight loss medication available in capsule form in the UK. It works differently to injectable treatments- rather than reducing appetite, it reduces the amount of fat your body absorbs from food.

• Xenical - prescription strength orlistat (120mg)
• Alli - lower strength orlistat (60mg), available without a prescription
• Orlistat - generic prescription version

A thorough assessment is the best way to find the treatment that suits you.

Yes. Mounjaro is prescription only. A registered healthcare professional should review your assessment before supply.

Mounjaro is a once-weekly injection. Best taken on the same day and time once every week.

Clinical trials show strong results. tirzepatide delivered average weight loss of up to 22.5% over 72 weeks in SURMOUNT-1 and stronger average results than semaglutide in SURMOUNT-5.

The most common Mounjaro side effects are nausea, diarrhoea, vomiting, and constipation. These symptoms are usually most noticeable when treatment starts or after a higher dose.

Read the patient information leaflet and the instructions for the Mounjaro pen before treatment starts. Speak to your doctor, pharmacist, or prescriber if anything is unclear.

You can buy Mounjaro online safely when a regulated service includes a clinical assessment, medical history review and pharmacy checks. Patients who buy Mounjaro online should look for real prescribing oversight and ongoing support.