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Tirzepatide Weight Loss Injection A once-weekly injection that helps you eat less, feel fuller for longer, and lose weight. Mounjaro® works differently — it targets two hunger hormones instead of one.
Start Free Consultation How it works
GPhC-registered pharmacy UK-licensed prescribers Discreet tracked delivery Genuine Eli Lilly product
~22.5% average body weight lost in clinical trials
(highest dose, 72 weeks) SURMOUNT-1 trial. Alongside a healthier diet and more activity. Results vary between individuals.
2 in 3 people lost 15% or more of their body weight
57% people lost 20% or more of their body weight
Why Mounjaro® What makes Mounjaro® different? Most weight loss injections work on one hunger hormone. Mounjaro® works on two — and that makes a real difference to how much weight people lose.
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It tackles hunger from two angles Mounjaro® mimics two hunger hormones — GLP-1 and GIP — at the same time. This helps you feel less hungry, feel satisfied sooner when you eat, and think about food less during the day. Other injections like Wegovy® only target one of these hormones, which is why Mounjaro® tends to work better for more people.
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It works on its own — no other medication needed Clinical trials tested Mounjaro® as a standalone treatment, with no other weight loss or diabetes medication involved. It worked well and was safe — with no serious low blood sugar events recorded at any dose when used on its own.
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One injection a week, whenever suits you Mounjaro® is injected just once a week, at any time of day, with or without food. Each pre-filled pen contains four doses — that's a whole month of treatment in one pen. Most people find it quick and straightforward once they've done it a couple of times.
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Made by Eli Lilly — a trusted name in medicines Mounjaro® is made by Eli Lilly, one of the world's largest pharmaceutical companies, and is fully licensed in the UK by the MHRA. We only supply genuine, regulated Mounjaro® from our registered pharmacy — never unverified alternatives.
About the Medicine What is Mounjaro®?
Mounjaro® is a prescription weight loss injection. The active ingredient is called tirzepatide, and it works by copying the effect of two natural hormones in your body that control hunger and how full you feel after eating. When you inject Mounjaro® once a week, it signals to your brain that you're less hungry and helps you feel satisfied with smaller meals. It also slows down how quickly food leaves your stomach, so you stay full for longer between meals. Mounjaro® is a prescription-only medicine — you need to complete an online consultation with a registered clinician first, who will check it's right for you. At Happy Pharmacy, that process is handled by our team of UK-registered prescribers.
~22.5% average body weight loss at highest dose
2 hunger hormones targeted (GLP-1 and GIP)
MHRA licensed in the UK for weight management
2 in 3 people lost 15%+ of body weight in trials
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How is it different from Wegovy®? Wegovy® (semaglutide) targets one hunger hormone (GLP-1). Mounjaro® targets two (GLP-1 and GIP). Because it works on both pathways simultaneously, it generally produces greater weight loss. In clinical trials, people on Mounjaro® lost more weight on average than those on semaglutide.
Clinical Evidence What do the studies actually show? Mounjaro® has been tested in large, well-designed clinical trials involving thousands of people. Here's what the research found — in plain terms.
~22.5% average body weight loss at highest dose (72 weeks)
2 in 3 people on highest dose lost 15%+ of body weight
57% people lost 20% or more of body weight
3.1% average weight loss with placebo (vs 20.9% on 15mg)
What happened in the weight loss trials? In the SURMOUNT-1 trial — the biggest weight management study — 2,539 adults who were overweight or living with obesity (but did not have diabetes) were given Mounjaro® or a placebo injection for 72 weeks (about 17 months).
  • People on the lowest dose (5 mg) lost around 15% of their body weight on average.
  • People on the highest dose (15 mg) lost around 20.9% on average — compared to just 3.1% with the placebo.
  • To put that in context: someone starting at 100 kg could expect to lose around 20 kg on the highest dose.
  • Around 2 in 3 people on the highest dose lost 15% or more of their body weight.
  • All participants also followed a healthier diet and increased how much they moved.
From the SURPASS-1 trial (Mounjaro® used on its own, no other medication, 40 weeks): average HbA1c reduction of 1.7% vs almost no change with placebo; around 6–8 kg weight loss vs less than 1 kg with placebo; more than half of people on higher doses reached normal blood sugar levels.
How does weight loss typically progress?
Stage Rough Timeframe What You Might Notice
Starting out (2.5 mg)Weeks 1–4Appetite may start to reduce; your body is adjusting
First increase (5 mg)Weeks 5–8Food cravings often reduce; early weight loss may begin
Building up (7.5 mg)Weeks 9–12Steady weight loss continues; feeling fuller after smaller meals
Maintenance (10 mg)Weeks 13–16Around 10–15% body weight loss typical at this stage
Higher dose (12.5 mg)Weeks 17–20For those who tolerate it well and want to go further
Maximum dose (15 mg)Week 21+Up to around 20–22.5% body weight loss seen in trials
*Based on average outcomes from clinical trials. Individual results vary. Not everyone needs to reach the highest dose to see meaningful results. Always follow a healthy diet and increase activity alongside treatment.
Low Blood Sugar Risk Will Mounjaro® cause low blood sugar? Low blood sugar (when your blood sugar drops too low, causing dizziness, shakiness, or fainting) is a concern with some diabetes medications. When Mounjaro® is used on its own — without insulin or other diabetes tablets — the risk is extremely low.
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Zero serious low blood sugar events at any dose In the SURPASS-1 trial, when Mounjaro® was used with no other medication, there were no serious hypoglycaemia events recorded at any dose — 5 mg, 10 mg, or 15 mg. This means no patient required assistance from another person due to low blood sugar.
Type of Low Blood Sugar Event 5 mg 10 mg 15 mg Placebo
Serious low blood sugar (needed help from another person) 0% 0% 0% 0%
Very low blood sugar reading (below clinical threshold) 0% 0% 0% 1%
From the SURPASS-1 trial: Mounjaro® used on its own, with no other diabetes or weight loss medication, over 40 weeks. Note: combining Mounjaro® with insulin or certain diabetes tablets does increase the risk — your prescriber will advise you.
Am I Eligible? Could Mounjaro® be right for me? Mounjaro® is a prescription medicine — a clinician must check it's safe and appropriate for you. At Happy Pharmacy, we use a three-pathway system to work out who qualifies. Eligibility is confirmed during your free online consultation. Our three pathways — which one applies to you?
Pathway Who It's For Min. BMI What This Means
1a Starting fresh — standard ≥ 30 A BMI of 30 or above is classed as obesity. No other health condition needed to qualify.
1b Starting fresh — with a health condition ≥ 27 A BMI of 27–29.9 can qualify if you also have a weight-related health condition (such as high blood pressure, type 2 diabetes, sleep apnoea, or others).
1c Starting fresh — adjusted for ethnicity ≥ Threshold −2.5 People from certain ethnic backgrounds carry a higher health risk at any given BMI. NHS guidance (NICE NG246) recommends a threshold 2.5 points lower for South Asian, Chinese, other Asian, Middle Eastern, Black African, and African-Caribbean backgrounds.
2 Switching from another provider ≥ 21 Already on a weight loss injection elsewhere? You can transfer if you have proof of your previous prescription, have lost at least 5% of your starting weight, and originally met Pathway 1 criteria.
3 Staying at target weight (maintenance) ≥ 20 If you've reached your target weight and it has been stable for 8–12 weeks, you may continue on the lowest dose that keeps you there. We will never prescribe below a BMI of 20.
Important: We will never prescribe Mounjaro® to anyone with a BMI below 20 — regardless of circumstances. Final eligibility is always confirmed by a registered clinician during your consultation.
✓ You're likely to be eligible if…
  • Your BMI is 30 or above (Pathway 1a)
  • Your BMI is 27+ with a qualifying health condition (Pathway 1b)
  • Your BMI meets standard threshold minus 2.5 points with qualifying ethnic background (Pathway 1c)
  • You're 18 or older
  • You're not pregnant or breastfeeding
  • You're willing to make some healthy changes to your diet and activity
  • You're switching from another UK provider and have lost at least 5% already (Pathway 2, BMI ≥21)
✗ Mounjaro® is not suitable if…
  • You are pregnant, trying to get pregnant, or breastfeeding
  • You have type 1 diabetes
  • You're already taking another weight loss injection (e.g. Wegovy®, Ozempic®)
  • You have, or have had, pancreatitis
  • You or a close family member have had medullary thyroid carcinoma (MTC) or MEN2
  • You have severe problems with your stomach or gut emptying
  • You are allergic to tirzepatide or any ingredients in Mounjaro®
  • Your BMI is below 20 at any point during treatment
This isn't a complete list. A clinician will always do a full review before prescribing.
Check your eligibility →
Treatment Plan How does the dosing work? Mounjaro® is always started at a low dose and increased slowly over several months. This gives your body time to adjust and helps to reduce the chance of side effects. Not everyone needs to reach the highest dose — some people do very well on a lower one.
Weeks Dose What's Happening at This Stage Stage
1–4 2.5 mg The starting dose — lets your body get used to the medicine Starting out
5–8 5 mg First increase — appetite control often starts to improve noticeably Building up
9–12 7.5 mg Gradual step-up — weight loss typically continues to progress Building up
13–16 10 mg Many people experience steady, meaningful weight loss here Maintenance
17–20 12.5 mg Higher dose for those who want to go further and are tolerating it well Maintenance
21+ 15 mg The maximum dose. Up to ~20–22.5% body weight loss was seen in trials. Not everyone needs this. Maximum dose
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What if I'm not losing enough weight? If you haven't lost at least 5% of your starting weight after 6 months on your maintenance dose, your prescriber will review your treatment. It doesn't automatically mean treatment stops — your doctor will look at the full picture and decide the best next step for you.
Pricing How much does Mounjaro® cost? Each pen contains four weekly injections — one pen covers one month. The price goes up as the dose increases, because higher doses contain more of the active ingredient. You'll only ever be prescribed the dose that's right for you clinically.
2.5 mg Weeks 1–4 £139.99 per month
5 mg Weeks 5–8 £174.99 per month
7.5 mg Weeks 9–12 £229.99 per month
10 mg Weeks 13–16 £254.99 per month
12.5 mg Weeks 17–20 £269.99 per month
Max dose 15 mg Week 21+ £299.99 per month
Prices shown are for the pen only. A consultation review may apply. Mounjaro® is only dispensed where it is clinically safe and appropriate. Prices may change.
In the box
  • Mounjaro® KwikPen™ (your prescribed dose)
  • Injection needles
  • Alcohol wipes & sharps bin
  • Patient information leaflet
Delivery
  • Plain, discreet packaging (no pharmacy branding)
  • Temperature-controlled packaging
  • Tracked delivery on all orders
  • Fast dispatch once approved
Support
  • Online prescriber consultation
  • Patient guidance leaflet
  • Pharmacist & prescriber support throughout
  • Regular clinical check-ins on your dose
Using Your Pen How to do your weekly injection Mounjaro® comes in a simple pre-filled KwikPen™. You inject it once a week, on the same day each week if possible. It can be done at any time of day and with or without food.
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Wash your hands thoroughly. Take the pen out of the fridge and give it a minute or two to warm up before you inject.
2
Attach a brand new needle. Never use the same needle twice or share your pen with anyone.
3
Choose where to inject: your tummy (at least 5 cm away from your belly button), your upper thigh, or your upper arm (if someone else is injecting you).
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Use a different spot each week. Moving around prevents soreness and skin irritation. Leave a finger-width of space between spots.
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Clean the skin with an alcohol wipe and wait for it to dry completely before you inject.
6
Press the pen firmly against your skin and press the button as instructed. Hold it in place until you hear or feel that all clicks have stopped.
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Remove the pen carefully and put the used needle straight into your sharps bin. Don't try to put the cap back on a used needle.
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Write down the date you injected. Try to do it on the same day each week so it becomes part of your routine.
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Store unused pens in the fridge (2–8°C). Once you've started using a pen, you can keep it at room temperature (below 30°C) for up to 30 days. Never freeze it.
Safety Information What side effects might I get? Like any medicine, Mounjaro® can cause side effects. Most are mild and improve on their own as your body adjusts — especially in the first few weeks or after a dose increase. The gradual dosing schedule is specifically designed to reduce the chance of side effects.
⚠ Very common (more than 1 in 10 people)
  • Feeling sick (nausea)
  • Diarrhoea
  • Not feeling hungry
  • Being sick (vomiting)
  • Constipation
  • Indigestion or an upset stomach
  • Stomach pain
⚠ Common (up to 1 in 10 people)
  • Tiredness
  • Redness, itching, or soreness where you injected
  • Dizziness
  • Heartburn or acid reflux
  • Temporary hair thinning
  • Gallstones (small stones in the gallbladder)
Rare but serious — contact a doctor or call 999 if you notice these
  • Pancreatitis: severe, constant stomach pain that doesn't go away, sometimes spreading to your back — stop injecting and get help immediately
  • Serious allergic reaction: swelling of your face, lips, or throat, difficulty breathing, or a spreading rash
  • Kidney problems caused by severe dehydration from vomiting or diarrhoea
  • Gallbladder problems: severe pain in the upper right side of your stomach, with fever or yellowing of the skin
If you're worried, call NHS 111. If it's a serious emergency like difficulty breathing or collapse, call 999. Report any side effects to the MHRA via the Yellow Card scheme or to Eli Lilly on 01256 315000.
Women's Health What do I need to know about contraception?
⚠ Important: the contraceptive pill may be less effective Mounjaro® slows down how quickly food moves through your stomach. This means it can also slow down how quickly your contraceptive pill is absorbed — which could make it less effective at preventing pregnancy. Because of this, the official guidance says: use an extra method of contraception (such as condoms) for 4 weeks after each time your dose is increased. If you experience severe vomiting or diarrhoea, this can also affect how well the pill works. Follow your pill's missed-dose guidance or ask your pharmacist.
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This is different from Wegovy® Wegovy® (semaglutide) does not require any change to your contraception. With Mounjaro®, additional contraception is needed for 4 weeks after each dose increase. Please discuss this with your prescriber during your consultation.
Pregnancy, fertility, and breastfeeding
  • Do not use Mounjaro® if you are pregnant. Stop treatment at least 1 month before trying to conceive.
  • Do not use Mounjaro® while breastfeeding.
  • Use effective contraception throughout your treatment.
  • The effect of Mounjaro® on fertility is not yet fully known.
FAQs Questions people often ask
Everyone is different, but the clinical trials give a good indication. In a large study, those on the highest dose (15 mg) lost an average of around 22.5% of their body weight over 72 weeks — about 22–23 kg for someone starting at 100 kg. Even at lower doses, results are significant. Your results will depend on your diet, how active you are, and how your body responds.
Most people notice a reduction in appetite within the first 1–2 weeks of starting treatment. Measurable weight loss typically begins within the first 4–8 weeks as the dose increases. Weight loss then tends to build gradually over the course of treatment.
Mounjaro® is a long-term treatment, not a short-term fix. Most people stay on it for at least 12 months to achieve meaningful, lasting results. If you stop treatment, your appetite is likely to return and some weight may come back over time. Your prescriber will review your progress regularly and advise on the right duration for you.
If you forget your injection, take it as soon as you remember — as long as it's within 4 days of your missed dose. If more than 4 days have passed, skip the missed dose and carry on with your next injection on your usual day. Never take two doses at the same time to make up for a missed one.
It's best to keep alcohol to a minimum, especially early in treatment. Alcohol can affect your blood sugar levels and may worsen some side effects like nausea. If you do drink, stick to small amounts with food and see how you feel.
You don't need to follow a rigid diet plan, but eating sensibly does make a big difference to your results. Smaller meals, less processed food, fewer high-fat or high-sugar items, and more fruit, vegetables, and protein will all help. Some people find that certain foods — particularly greasy or spicy ones — can trigger nausea early in treatment.
Possibly, yes — this is an important one to know. Mounjaro® can slow down how the pill is absorbed, which might make it less effective. The official guidance recommends using an additional contraceptive method (like condoms) for 4 weeks after each dose increase. Talk to your prescriber about this during your consultation. Note this is different from Wegovy®, which does not require any change to contraception.
Yes. As a prescription medicine, Mounjaro® is allowed in hand luggage when flying. Keep it in its original packaging and carry your prescription or a covering letter from your pharmacy. It needs to stay refrigerated (2–8°C) but can be kept at room temperature (below 30°C) for up to 30 days once in use.
Both are once-weekly injections that help with weight loss, but they work differently. Wegovy® (semaglutide) targets one hunger-regulating hormone (GLP-1). Mounjaro® targets two (GLP-1 and GIP). In trials, Mounjaro® generally produced greater weight loss on average. However, Wegovy® has been specifically approved to reduce the risk of heart attacks and strokes in people who already have heart disease — Mounjaro® doesn't currently have that specific approval for weight management.
Yes, and it's encouraged. Regular movement — even just brisk walking — improves your results and supports long-term weight maintenance. Some people find their energy levels improve as they lose weight, making it easier to be more active over time.
Mounjaro® is a prescription-only medicine — it cannot legally be sold without a prescription from a registered clinician. At Happy Pharmacy, you complete a free online consultation which is reviewed by a UK-registered prescriber. Only then is it dispensed by our GPhC-registered pharmacy and delivered to you discreetly. Never buy it from unregulated websites or social media sellers — counterfeit products are a serious health risk.
References & Clinical Sources Where our information comes from All clinical claims in this document are based on published peer-reviewed evidence, licensed prescribing information, and current UK regulatory guidance.
Source Detail
SURPASS-1 Rosenstock J et al. Effect of tirzepatide monotherapy on glycaemic control in adults with type 2 diabetes. Lancet. 2021;398(10295):143–155.
SURPASS-2 Frías JP et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021;385(6):503–515.
SURMOUNT-1 Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205–216.
Mounjaro® SmPC Mounjaro® (tirzepatide) Summary of Product Characteristics. Eli Lilly and Company. Available at: electronic Medicines Compendium (emc). Last updated 2024.
NICE NG246 National Institute for Health and Care Excellence. Obesity: identification, assessment and management. NICE guideline NG246. Published 2025.
NICE TA1026 National Institute for Health and Care Excellence. Tirzepatide for managing overweight and obesity (TA1026). Published 2025.
NICE TA875 National Institute for Health and Care Excellence. Semaglutide for managing overweight and obesity (TA875). Published 2023.
MHRA Medicines and Healthcare products Regulatory Agency. Mounjaro® (tirzepatide) — MHRA approval for weight management. November 2023.
This page is intended for patient information purposes only and does not constitute medical advice. Always follow the guidance of your prescribing clinician and refer to the full Mounjaro® SmPC for complete prescribing information. Adverse events should be reported to the MHRA via the Yellow Card scheme (yellowcard.mhra.gov.uk) or to Eli Lilly on 01256 315000. Happy Pharmacy is a GPhC-registered pharmacy (GPhC No. 9012585). Factsheet data: May 2026.
ResourcesDownload Information FilesDownload our patient information leaflets, clinical summaries and prescribing guides.
PDF
Mounjaro® FactsheetKey Information about Mounjaro.
5.5 MBNo file linked
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Mounjaro® BrochureGuidance and information for adultswho have been prescribed Mounjaro®for weight management
5.5 MBNo file linked
Ready to start your weight loss journey? Complete your free online consultation. Reviewed by a UK-registered prescriber and dispensed by a GPhC-registered pharmacy. Start Free Consultation →
Happy Pharmacy is a GPhC-registered pharmacy (GPhC No. 9012585). All medicines are supplied only following clinician assessment and where clinically appropriate. Factsheet data: May 2026.
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