Your guide to tirzepatide: Weight loss effectiveness and how to access it

From Wegovy to Rybelsus and now Mounjaro, it seems like there are new weight loss medications popping up on the scene every few months.

And, it can get pretty overwhelming to understand how each medication works, who can access it and whether it's right for you and your weight loss journey.

Tirzepatide (otherwise known by the brand name Mounjaro) is a weight loss and type 2 diabetes medication that has recently gained attention. That's because it's both a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) receptor agonist medication — the first of its kind.

As the first dual GIP and GLP-1 medication, tirzepatide is showing impressive weight loss results in clinical trials and clinical practice.

So, what's the deal with tirzepatide and how does it work for weight loss and as a type 2 diabetes and obesity treatment? If you're looking to learn more about tirzepatide then we're diving deep into everything you need to know about this drug, how it works and whether Mounjaro is available in the UK.

What is tirzepatide?

Tirzepatide is a medication used to help patients with type 2 diabetes navigate glycemic control (lower blood sugar) and lose weight. Type 2 diabetes is a long-term health condition where blood sugar levels are too high due to the body not producing enough insulin or not producing insulin properly.

This can lead to other serious health problems like increased cardiovascular risk, kidney disease, and obesity. Tirzepatide works to lower blood sugar levels by increasing the production of insulin and decreasing the amount of sugar produced by the liver [1].

Like other weight loss drugs, tirzepatide also slows down how food is metabolised by the body, which in turn makes people feel fuller for longer and aids in weight loss and body weight reduction [1].

How does tirzepatide work for weight loss?

As a dual GIP and GLP-1 receptor agonist, tirzepatide works on the glucose-dependent insulinotropic polypeptide (GIP) receptor agonist and the glucagon-like peptide 1 (GLP-1) receptor agonist.

You may have heard the term glucagon-like peptide 1 before because that's the receptor agonist that other weight loss and diabetes medicines, like Wegovy, target.

But, what makes tirzepatide different is it's the first combination of 2 classes of medications, the GIP and GLP-1 receptor agonist which are both incretin hormones that are released after food intake.

Tirzepatide works by mimicking both of these receptor agonists, which includes processes like alerting the pancreas to stop releasing insulin after eating and sending signals to the liver to decrease glucose levels [2].

In turn, this not only helps you feel fuller for longer but it slows down digestion, and aids in glycemic control, which all lead to weight loss and weight management [2].

Clinical trials have shown that tirzepatide has beneficial effects on helping those with type 2 diabetes and obesity lose weight and aids in weight management too. A clinical trial with over 2500 people who were either obese or overweight was split into 2 treatment groups: people taking tirzepatide and people in the placebo group.

The clinical trial showed a weight loss of 15-20% of their starting body weight in 72 weeks for people taking tirzepatide. On the other hand, those in the placebo clinical trial group only showed average weight reductions of 3% [3].

What are the side effects of tirzepatide?

Like all medications, tirzepatide does have some side effects. While most side effects tend only to occur when first starting the treatment or increasing the dose, they're still important to keep in mind when deciding to take tirzepatide [4].

The most common side effects of tirzepatide are [4]:

• Vomiting
• Nausea
• Diarrhoea
• Loss or decreased appetite
• Abdominal pain
• Constipation

Aside from these common side effects, tirzepatide can also cause low blood sugar and its advised to seek medical attention if you experience any of these adverse effects [4]:

• Dizziness
• Blurred vision
• Anxiety, mood changes or irritability
• Sweating
• Slurred speech
• Headaches
• Fast heart rate

It's also important to note that tirzepatide does have some other potentially serious side effects and adverse events including [4]:

• Serious allergic reaction: Allergic reactions can cause breathing difficulties and rashes, so it's important to seek urgent medical care if you experience a severe allergic reaction.
• Thyroid cancer: In animal clinical trials and studies, tirzepatide has caused thyroid cancer and thyroid tumours, including medullary thyroid carcinoma (MTC). While the relevance in humans is low, this can't be completely ruled out. If you have a personal or family history of thyroid cancer, it's advised not to take this diabetes and obesity medicine.
• Pancreatitis: Tirzepatide can cause severe abdominal pain or back pain, fevers and vomiting which requires treatment discontinuation and immediate medical attention.

How is tirzepatide administered?

Tirzepatide is administered as a weekly subcutaneous injection, meaning the pre-filled pen is injected under the skin, usually in the stomach, thigh or upper arm. Tirzepatide can also be administered with or without meals at any point in the day [5].

You should follow the dosing schedule recommended by your doctor. In general terms, a typical dosing schedule starts with a low dose and is gradually increased to 5mg once a week after 4 weeks of treatment. If you require further glycaemic control, the dosage can be increased to 10mg once a week.

It's also important to note that you can take insulin in the same area as tirzepatide but they shouldn't be given right next to one another, nor should they be mixed in the same injection [5].

Is tirzepatide prescription only?

Tirzepatide is a prescription-only medication that can be given to patients with type 2 diabetes alongside lifestyle changes like improving your diet and increasing exercise levels.

Tirzepatide is available via prescription from private clinics, like Juniper, or via the NHS, although the eligibility criteria for the latter is incredibly strict.

As of late June 2025, Mounjaro is available on the NHS for weight loss and can be obtained at GP surgeries in England. Previously, only Wegovy and Saxeda were available on the NHS, however these could only be accessed with a referral to an NHS specialist weight management service.

The initial rollout of Mounjaro on the NHS is planned to reach 220,000 people over 3 years. To be eligible to receive Mounjaro from a GP or community clinic over the next 3 years, the person must meet the following criteria:

Year 1

• BMI ≥ 40 (or ≥ 37.5 for some ethnic groups)
• 4 or more weight-related comorbidities (e.g. type 2 diabetes, high blood pressure, sleep apnoea)‍

‍Year 2

• BMI 35 to 39.9
• Still require 4 or more co-morbidities‍

‍‍Year 3

• BMI ≥ 40
• 3 or more co-morbidities

Alternatively, a few of the eligibility guidelines requirements of Mounjaro via private clinics include:

• You have a body mass index (BMI) of 30 or more, indicating obesity
• You have a BMI of 27 or higher, categorised as overweight, coupled with at least one weight-related health condition such as high blood pressure or type 2 diabetes

How to know if Mounjaro is right for your weight loss journey

For many, weight loss medications like Mounjaro can be life-changing — especially if they've attempted to lose weight through diet and lifestyle changes, to no avail.

However, it's not the right option for everyone. For starters, Mounjaro can only be prescribed to people with a body mass index (BMI) of over 30, or a BMI between 27 to 30 with a weight loss-related condition.

It's also important to note that not all weight loss drugs are created equal. One person may experience zero side effects when starting Mounjaro, while others might be better suited to Wegovy. The best way to start weighing up your options is to take our short questionnaire.

Just by answering a few questions about your lifestyle, health, family history, and any other medications you might be taking, you can take your first step towards a healthier you.

Mounjaro vs Wegovy

Both Wegovy and Mounjaro are considered the gold standard when it comes to aiding weight loss efforts. Thus far, the two medications haven't been directly compared to each other in medical trials.

It's long been thought that Mounjaro leads to more significant weight loss outcomes than Wegovy but with recent research, that is changing.

In clinical trials, patients on the highest possible dose of Wegovy lost up to 20.7% of their body weight, compared to 20.9% with Mounjaro at its highest dose — showing that both can be highly effective when used consistently and with the right support [6][7]. With Juniper, Wegovy is delivered as part of a complete programme that includes expert care, support and tracking tools — to help you get the most from your treatment.

This higher dose of Wegovy isn’t available just yet, but it’s expected to launch in the UK soon.

Can you switch from Mounjaro to Wegovy?

As of 1 September 2025, Eli Lilly, the manufacturer of Mounjaro (tirzepatide), increased its UK list price to align with other developed countries. This nationwide change applies to providers including pharmacies, private clinics, and digital platforms.

In response, we’ve lowered the price of our Wegovy programme by 25%, and we’re making it easier for patients to switch without starting over, so that effective treatment remains within reach for as many people as possible.

So, if you've been wondering if you can switch from Mounjaro to Wegovy, the good news is that it's both safe and straightforward.

When making the switch, Juniper patients don’t need to restart at the lowest dose. If clinically appropriate, they can continue at a higher dose aligned with recent treatment history. We also only require a 7-day gap between your last Mounjaro dose and your first Wegovy dose — unlike most providers, who require 28 days.

At Juniper, we make that switch seamless and fully supported — so you can protect your progress without paying more than you need to. Our clinical switching protocol is is simple and safe:

• Review — Your clinician assesses your treatment history and dose tolerance.
• Match — If eligible, you start on an equivalent high dose to avoid losing progress.
• Transition — Only a 7-day window is required between your last Mounjaro dose and your first Wegovy dose (most providers require 28 days).
• Support — Pharmacist check-ins, dose adjustments, and lifestyle guidance keep you on track.

Start your Wegovy switch today →

Is tirzepatide available for weight loss in the UK?

Yes, it is. Mounjaro, with it's GLP-1 and GIP combination, is a medication option, alongside Wegovy, which is a GLP-1 medication, in the Juniper Programme. Our programme combines clinical care, health tracking and community support with weight loss medication for those who are aged between 18 and 75 and meet our strict eligibility criteria.

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