Mounjaro Weight Loss Injections

Mounjaro is a prescription only treatment which functions by mimicking the action of hormones that target areas of the brain involved in appetite regulation. By administering a once-weekly injection under the skin, Mounjaro can help significantly reduce food cravings and make you feel fuller for longer. Clinical trials have demonstrated Mounjaro’s ability to help patients reduce their bodyweight by up to ~22% making it a highly effective option for weight loss.

This life changing treatment is available through our UK-registered online prescribing service, ensuring a convenient and secure route to commence your weight loss journey. After completing our online assessment with our team of clinicians, eligible individuals will have their prescriptions processed in 24 hours. Our dedicated pharmacy team then prepares and dispatches the treatment directly to you, ensuring a seamless transition to a healthier lifestyle.

Mounjaro weight loss injections are suitable for adults who meet specific clinical criteria and can safely use it under medical guidance. You may be eligible for Mounjaro weight loss injection treatment if you meet one of the following:

• Have a BMI of 30 kg/m² or above (clinically obese)

• Have a BMI of 27–30 kg/m² (overweight) with a weight-related condition such as high blood pressure, high cholesterol, pre-diabetes, or heart disease

• Are from a ethnic background, where lower BMI thresholds may apply (typically from 27.5 kg/m²) due to increased metabolic risk

• Are transferring from another provider and wish to continue injecting Mounjaro with our service

To start using Mounjaro, you must not have medical conditions or be taking medications that could interact with treatment. Complete our online assessment to check your eligibility and learn how long you may need to stay on Mounjaro injections.

Can you get Mounjaro on the NHS?

Yes, Mounjaro weight loss injections are available on the NHS for some patients, but access is currently limited. Not all GP practices prescribe the Mounjaro weight loss injection, as availability depends on local NHS services and strict eligibility criteria.

NICE has approved tirzepatide (the active ingredient in the Mounjaro pen) for weight management. The NHS rollout is being introduced over a phased period over several years, with priority given to patients with the highest medical need. As a result, many people may not yet qualify and may need to consider private treatment options if they want to start injecting Mounjaro sooner.

Who Is Eligible for Mounjaro on the NHS?

To qualify for Mounjaro during the initial rollout, you must have:

• A BMI of 40 or above, and
• At least four of the following conditions:

1. High blood pressure
2. High cholesterol or abnormal blood fats
3. Obstructive sleep apnoea
4. Heart or cardiovascular disease
5. Type 2 diabetes

Mounjaro, contains the active ingredient tirzepatide, it’s a once-weekly injectable medicine that targets two key receptors involved in metabolic regulation: the glucagon-like peptide-1 (GLP-1) receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor.

Tirzepatide’s dual action is at the core of its effectiveness. By acting as an agonist for both GIP and GLP-1 receptors, Mounjaro taps into the body’s own mechanisms for regulating appetite and energy balance. GIP plays a critical role in managing energy balance through its action on brain and adipose tissue receptors, contributing to a regulation of food intake and energy expenditure. The GLP-1 receptor helps lower blood sugar levels and appetite regulation which means those on Mounjaro have less cravings, leading to weight loss.

Has Mounjaro been clinically tested?

The SURMOUNT-1 trial, among others, has provided compelling evidence of Mounjaro’s efficacy in weight management. Participants without diabetes but with obesity or overweight status experienced significant weight reduction, underscoring the potential of this dual-agonist approach. These trials have not only confirmed the weight loss capabilities of tirzepatide but also highlighted its safety profile, making it a promising option for those eligible.

How does Mounjaro work chemically?

Mounjaro’s molecular mode of action is fascinating. The peptide is engineered from the native GIP sequence to precisely target the GIP and GLP-1 receptors. Its affinity for the GIP receptor is comparable to that of native GIP, while its binding to the GLP-1 receptor, although slightly weaker, is sufficiently potent to activate the receptor’s weight loss mechanisms. This dual receptor activation is thought to synergize, enhancing the weight loss effect beyond what could be achieved through GLP-1 receptor activation alone.

The GIP component is believed to act centrally, augmenting the weight loss induced by GLP-1, while also targeting white adipose tissue to improve lipid storage and prevent dietary lipid spillover. This mechanism is crucial for managing the body’s energy and lipid metabolism, offering a protective effect against the accumulation of excess body fat.

Most patients begin to notice early weight changes within the first 2–4 weeks of starting Mounjaro weight loss injections, with more significant results developing over 8–12 weeks as the dose is gradually increased.

Average weight loss on different Mounjaro doses

Key points about Mounjaro weight loss injection results:

• Early effects (2–4 weeks): Reduced appetite and improved portion control after starting the Mounjaro pen.

• Progressive weight loss (8–12 weeks): Visible fat loss as the dose is titrated safely.

• Maximum results (up to 72 weeks): Clinical studies show up to 22.5% body weight loss on the highest dose when injecting Mounjaro alongside lifestyle changes.

• Dose escalation matters: Gradual increases help minimise side effects and improve long-term results.

• Best outcomes: Achieved when Mounjaro weight loss injections are combined with a balanced diet and at least 150 minutes of weekly physical activity.

• Additional benefits: Improvements in waist circumference, blood pressure, cholesterol levels, and insulin sensitivity.

This efficacy is backed by robust clinical trials. The phase 3 multicenter, double-blind, randomized, placebo-controlled trial, involving 119 sites across nine countries, highlights Mounjaro’s superior performance over placebo in substantial weight loss among participants. Over a 72-week treatment period, which included a comprehensive lifestyle intervention, participants on tirzepatide experienced significant weight reductions—15.0%, 19.5%, and 20.9% for the 5mg, 10mg, and 15mg doses, respectively, compared to a 3.1% reduction with placebo.

Mounjaro is available in multiple dosages: 2.5mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg solutions for injection, each supplied in one pre-filled pen designed for easy use. Before using Mounjaro, always read the instructions for use and the package leaflet provided with your pen for the latest information and guidance.

• Initial Phase: Start with 2.5 mg once weekly for the first four weeks.
• Titration: Increase the dose in 2.5 mg increments every 4 weeks as advised, up to a maintenance dose of 5 mg, 10 mg, or 15 mg weekly, depending on tolerance and response.

Concerned about giving yourself an injection?

“Many patients feel anxious about the idea of self-injecting at first. However, Mounjaro is designed to make the process as straightforward and comfortable as possible. It is supplied in a pre-filled pen device rather than a traditional syringe, making administration simple and controlled. The needle used is very fine and significantly smaller than those typically used for routine injections, and the pen mechanism delivers the dose, without the need for manual pressure.”
– Sunny Dhain MPharm, PGDip Independent Prescriber, Clinical Director

How to use Mounjaro pens?

1. Timing: Administer Mounjaro once a week, ideally on the same day and time, to maintain steady medication levels.
2. Injection Sites: Inject into the abdomen, upper thighs, or outer section of the upper arms. Avoid veins and muscles. Rotate injection sites within these areas to reduce irritation.

1. Preparation: Use a new needle for each injection. Inspect your pen and needle for damage and ensure the medication is clear and colourless to slightly yellowish.
2. Dosing Schedule: Begin with a 2.5 mg dose once a week for 4 weeks, then increase the dose as directed, following a titration schedule to optimise efficacy and minimise side effects.

Troubleshooting a Mounjaro Pen

• Air Bubbles: Normal in the pen and do not affect the dose.
• Room Temperature: There’s no need to warm the pen before use.
• Post-Injection Leakage: A drop of liquid or blood on the skin post-injection is normal. Apply gentle pressure with a cotton ball or gauze without rubbing the site.

How to dispose used Mounjaro?

• Each pen should be disposed of properly in a sharps bin after administration.
• Always use a new needle for each injection to prevent infection and ensure sterility.

Monitoring and Adjustments

• Monitor your body’s response to Mounjaro. Adjustments to the dosage may be necessary based on effectiveness and side effects.
• If adding Mounjaro to other diabetes medications like sulphonylureas or insulin, monitoring and dose adjustments may be needed to reduce the risk of hypoglycemia

You cannot use Mounjaro if you:

• Are pregnant or planning pregnancy
• Are breastfeeding
• Are over 85 years old
• Have severe stomach or gut conditions (such as severe gastroparesis)
• Have certain types of diabetic retinopathy
• Have been diagnosed with acute pancreatitis

Use Mounjaro with caution if you:

Have a history of pancreatitis
Mounjaro has not been widely studied in patients with previous pancreatitis. Stop treatment immediately and seek medical help if you develop severe stomach pain, nausea, or vomiting.

Take insulin or sulphonylureas
Using Mounjaro alongside insulin or sulphonylurea medicines can increase the risk of low blood sugar (hypoglycaemia). Your prescriber may need to adjust your dose and monitor you closely.

Experience severe gastrointestinal side effects
Common side effects such as nausea, vomiting, or diarrhoea can lead to dehydration, which may affect kidney function — particularly in older adults. Staying well hydrated is important.

Take other oral medications
Mounjaro can slow stomach emptying and affect how some oral medicines are absorbed, especially those with a narrow therapeutic range. Your prescriber may review your medication regimen.

What Are the Most Common Side Effects of Mounjaro?

• diarrhea,
• nausea,
• vomiting,
• constipation,
• and low blood sugar, particularly when taken with certain diabetes medications.

Can Mounjaro Cause Low Blood Sugar?

What Are Other Common Side Effects of Mounjaro?

• fast pulse,
• allergic reactions like eczema or itching,
• stomach pain,
• indigestion,
• bloating,
• gas,
• heartburn,
• fatigue,
• increased pancreatic enzymes,
• irritation at the injection site,
• low blood pressure,
• dizziness,
• hair loss.

Are There Any Uncommon Side Effects of Mounjaro?

Does Mounjaro Have Any Long-Term Side Effects?

What Should I Do If I Experience Serious Side Effects From Mounjaro?

The list above does not include all possible side effects, therefore it is vital that if you experience any serious side effects whilst using this medication to consult a healthcare professional and if you experience side effects not listed above, complete a MHRA Yellow Card report. 

Be sure to read through the patient information leaflet before taking any new medication to familiarise yourself with the possible side effects, cautions, and contraindications. You should only take Mounjaro once you have understood all the warnings and precautions. If you are concerned discuss this with your doctor or a The Family Chemist clinician. 

Weight Loss Treatment Comparison

Several alternatives to Mounjaro are available for weight management, each using different active ingredients and mechanisms to support weight loss. The options below are commonly prescribed in the UK:

To explore weight-loss treatments, visit The Family Chemist weight loss treatment page and begin your medically supervised weight-management journey with guidance from our prescribing team.

Mounjaro and Wegovy are weekly weight-loss injections available in the UK that help reduce appetite and support long-term weight management. Both are clinically proven, but they use different active ingredients and work slightly differently in the body.

Mounjaro contains tirzepatide, which targets two appetite-regulating hormones (GLP-1 and GIP). Wegovy contains semaglutide, which targets the GLP-1 hormone alone.

The right option depends on your weight-loss goals, and how well you tolerate treatment.

We have created a guide about the differences between Mounjaro and Wegovy.

Research shows that taking a single dose of tirzepatide can slightly reduce the effectiveness of your oral contraceptive. Specifically, the peak concentration (Cmax) and the overall exposure (AUC, which measures how much of the drug is in your bloodstream over time) of the hormones in your birth control pill are decreased.

If you miss a dose, take it as soon as you remember within 4 days. If it’s been more than 4 days, skip the missed dose and return to your regular schedule without doubling up. Speak to our clinician if you miss several doses as you may have to retitrate your dose. 

You can change the day of your weekly injection if needed, ensuring there’s at least a 3-day gap between doses.

How long you remain on Mounjaro weight loss injections varies based on your weight loss targets, clinical response, and long-term maintenance strategy. Research from the SURMOUNT-4 trial found that people who stayed on the Mounjaro weight loss injection were more likely to preserve their results and continue losing weight, while those who stopped treatment were more prone to weight regain. Your prescriber will monitor your progress and make dose adjustments to your Mounjaro pen where needed to ensure safe and effective use. When injecting Mounjaro, get the best results by following a balanced diet and exercise plan.

Mounjaro weight loss injections are designed to be used once per week. 

You can take your weekly dose at any time of day, with or without meals. The most important factor is consistency. Choose a specific day that fits easily into your routine and aim to inject Mounjaro at roughly the same time each week. Many patients find setting a phone reminder helpful to avoid missing a dose.

Changing Your Injection Day

If you need to adjust the day you take your Mounjaro weight loss injection, make sure there is a minimum gap of 72 hours (3 days) between doses. Once the new day is established, continue injecting Mounjaro weekly as normal.

Frequent changes to your dosing schedule are not recommended, as this may affect how well the medication works. Keeping a regular routine helps the Mounjaro pen deliver consistent results and supports steady progress.

When you stop taking Mounjaro weight loss injections your body may partially reverse the changes achieved while you were injecting Mounjaro. Evidence from the SURMOUNT-4 trial shows that stopping Mounjaro weight loss injections often leads to partial or significant weight regain. After 36 weeks of treatment using the Mounjaro pen, participants who lost at least 10% of their body weight were switched to a placebo. Over the following 52 weeks, 82% regained at least 25% of the weight they had lost, 24% regained 75% or more, and 9% regained all of the lost weight, despite receiving diet and exercise support. This suggests that the appetite-regulating and metabolic effects seen while injecting Mounjaro tend to diminish once treatment stops if you stop eating a balanced diet and dont take part in regular physical activity to help prevent weight gain when they come off the medicine.

Is weight regain inevitable after stopping the Mounjaro weight loss injection?

Not necessarily. Although the SURMOUNT-4 data shows a strong trend toward weight regain, this does not mean every patient will regain the same amount. Some participants maintained part of their weight loss through structured lifestyle changes, including calorie control and regular physical activity. In addition, researchers highlighted limitations such as incomplete tracking of diet and exercise habits and the fact the trial was industry funded, meaning further independent research is needed.

Mounjaro weight loss injections are supplied in six different strength options. The dosing plan follows a gradual step-up approach, allowing your body time to adjust while supporting safe and effective weight loss.

The following Mounjaro weight loss injection strengths are currently available:

• 2.5mg

• 5mg

• 7.5mg

• 10mg

• 12.5mg

• 15mg

Mounjaro Dosing Options

Treatment with the Mounjaro pen begins at 2.5mg once weekly. This starting dose is used for the first four weeks and helps reduce the chance of early side effects while your body adapts to the medication.

After this initial phase, you may increase your dose to 5mg for a further four weeks. If additional weight loss support is needed and the treatment is well tolerated, your dose can be increased in steady 2.5mg stages at four-week intervals. The highest approved dose for injecting Mounjaro is 15mg per week.

You should never increase your dose earlier than advised. Raising your dose too quickly or exceeding the maximum strength may increase the risk of side effects such as nausea, stomach discomfort, dehydration, and fatigue. Always follow your prescriber’s instructions when adjusting your Mounjaro pen dosage.

Reaching the highest dose is not necessary for everyone. Many patients achieve strong results at moderate doses and choose to remain on a level that provides consistent weight loss with fewer side effects. While higher doses of Mounjaro weight loss injections may enhance appetite control, they may also increase the likelihood of side effects and overall treatment cost.

Step-by-Step Instructions

1. Wash your hands
   Wash your hands thoroughly using soap and water before preparing your injection.
2. Prepare the pen
   Check the Mounjaro pen carefully. Ensure:
   • It is not expired
   • It is not damaged
   • The liquid looks clear and normal
3. Do not use the pen if anything appears unusual.
4. Attach a new needle
   Attach a new needle securely to the pen.
   Always use a new needle for each injection.
5. Turn the dose knob
   Slowly turn the dose knob until you hear two clicks.
6. Prime the pen
   Prime the pen to release any air bubbles and confirm it is working correctly.
7. Set the dose
   Adjust the dosage to ‘1’.
8. Inject the medication
   • Insert the needle into your skin
   • Push down the dose knob
   • Count slowly to 5
9. Remove the needle
   Pull the needle out and check that the dose count has returned to ‘0’.
10. Dispose and store
    Remove the needle safely and replace the pen cap.
11. Take weekly at the same time
    Take your injection at the same time each week (a time that suits you) to achieve the best effect and reduce the chance of missed doses.

A Mounjaro maintenance dose refers to the dose you continue using long term to help sustain weight loss or maintain your target weight once it has been achieved.

According to the manufacturer, typical maintenance doses are 5mg, 10mg, and 15mg. However, the most appropriate maintenance dose can vary between individuals. Many people remain on the dose that feels most effective and manageable for them, in consultation with their prescriber.

Mounjaro can be purchased online in the UK through a regulated private prescription service such as The Family Chemist, where patient safety and clinical suitability are prioritised.

The process begins with a short online weight loss medical questionnaire covering your health history, current medications, and weight-loss goals, which is reviewed by a qualified prescriber to determine whether treatment is appropriate. If approved, your prescription is issued and the medication is dispensed and delivered directly to your door, alongside access to diet, lifestyle, and weight-management guidance for a more holistic approach.

Patients can log into their online account at any time to track progress and message a clinician for support while using Mounjaro.

Buying Mounjaro online should always involve a regulated pharmacy and a proper clinical assessment. This ensures the medication is appropriate for your medical history and that you have access to professional support while using it.

At The Family Chemist, patients benefit from a structured online pathway, medical oversight, and ongoing guidance — helping you stay informed, supported, and confident throughout your weight-loss journey.

When you begin treatment with The Family Chemist, you’ll receive access to a complimentary support programme created by our in-house nutritionists and clinicians. This package is designed to help you build sustainable habits alongside your medication and includes practical guidance on healthy eating, physical activity, and structured planning tools. You’ll also receive easy-to-use trackers and goal-setting templates to keep your weight-loss journey organised, focused, and measurable.

If you ever have questions during treatment, our Weight Loss Service FAQ provides clear, reliable answers to the topics patients ask about most — from dosing and side effects to lifestyle support and progress expectations.

Start your weight-loss journey with confidence

Beginning treatment is simple, clinically guided, and built around your needs:

• Complete a short medical questionnaire online

• Our prescribing clinicians review your information to confirm suitability

• Receive personalised next steps and your free support package

• Choose and request your treatment securely

Take the first step towards a healthier weight with expert support from The Family Chemist combining medical care, nutrition guidance, and ongoing encouragement to help you achieve long-term results.

Request your treatment now

• Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2): a double-blind, randomised, multicentre, placebo-controlled, phase 3 trial (2023) The Lancet [accessed 9^th February 2026]
• Tirzepatide Once Weekly for the Treatment of Obesity (2022) The New England Journal of Medicine [accessed 9^th February 2026]
• Mounjaro 2.5/5/7.5/10/12.5/15mg KwikPen solution for injection in pre-filled pen (2024) EMC: Patient Information Leaflet [accessed 9^th February 2026]
• Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen, emc [accessed 9^th February 2026]
• A Study of Tirzepatide (LY3298176) in Participants With Type 2 Diabetes Who Have Obesity or Are Overweight (SURMOUNT-2) (2024) Clinical Trials [accessed 9^th February 2026]
• A Study of Tirzepatide (LY3298176) In Participants After A Lifestyle Weight Loss Program (SURMOUNT-3) (2024) Clinical Trials [accessed 9^th February 2026]
• Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity (2024) JAMA [accessed 9^th February 2026]
• Mounjaro is the first in a new class for the treatment of type 2. Diabetes (2023) Mounjaro [accessed 9^th February 2026]
• How to use Mounjaro (2023) Mounjaro [accessed 9^th February 2026]
• MHRA authorised diabetes drug Mounjaro (tirzepatide) for weight management and weight loss (2023) GOV.UK. [accessed 9^th February 2026]
• Effectiveness of Dulaglutide in the Real World and in Special Populations of Type 2 Diabetic Patients (2020) NIH [accessed 9^th February 2026]
• Lilly’s SURMONT-2 results published in The Lancet show tirzepatide achieve a mean weight reduction of 15.7% at the highest dose (15mg) in adults with obesity or overweight and type 2 diabetes (2023) Eli Lilly [accessed 9^th February 2026]
• Tirzepatide for managing overweight and obesity (2024) NICE [accessed 9^th February 2026]
• Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial (2022) Nature Medicine [accessed 9^th February 2026]
• Once-Weekly Semaglutide in Adults with Overweight or Obesity, The New England Journal of Medicine [accessed 9^th February 2026]

How do I request Mounjaro from The Family Chemist?

Is there a cheaper alternative to Mounjaro available in the UK?

How much weight can you realistically lose on Mounjaro?

Can I get Mounjaro without a prescription?

How should Mounjaro be stored at home?

Why might I not be losing weight on Mounjaro yet?

• You may still be building up to a higher dose.
• Treatment may take longer to take effect.
• Diet and physical activity still play a key role.
• Plateaus are common during weight loss.

Is Mounjaro approved for weight loss in the UK?

How much does Mounjaro cost privately?

Can I switch from Mounjaro to another weight-loss injection like Wegovy?

What is the typical week-by-week weight loss on Mounjaro?

Can I stop Mounjaro and restart later?

Can I travel with Mounjaro pens?

• Carry pens in your hand luggage.
• Take a prescription or travel letter.
• Use a cool bag in transit.
• Refrigerate at your destination, where possible.
• Pack enough medication and needles for your trip.

How long can Mounjaro stay out of the fridge?

Can I drink alcohol while taking Mounjaro?

Can Mounjaro affect the contraceptive pill?

Can Mounjaro be prescribed on the NHS?