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

Can you switch from tirzepatide (Mounjaro) to semaglutide (Wegovy)?

If you're thinking about switching 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.

Plus, our switching protocol has only a 7-day gap between medications, compared to 28 days with most other providers. Our clinical oversight ensures safe, effective transitions — helping patients maintain momentum without compromising care.

You can switch in a few easy steps. Simply answer some quick questions about your medical history and goals and choose whether to continue on your current medication or switch to an equivalent dosage in the same trusted GLP-1 class of medications. From here, our clinicians will work with you to find the best treatment plan.

Not only can Wegovy offer similar results to Mounjaro, but it's also more affordable.

In clinical trials, patients on the highest possible dose of Wegovy lost up to 20.7% of their body weight [6], compared to 20.9% with Mounjaro at its highest dose [7] — showing that both can be highly effective when used consistently and with the right support. Plus, because Wegovy has been available for longer than many newer medications, it is generally more accessible and cost-effective over time.

With Juniper, Wegovy is delivered as part of a complete programme that includes expert care, coaching, and tracking tools — to help you get the most from your treatment.

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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