Weight loss treatments

(GLP-1 agonists)

What are they used for?

Tirzepatide has been licensed for the treatment of diabetes under the brand name “Mounjaro” since 2023, liraglutide as “Victoza” since 2009, semaglutide as “Ozempic” since 2015, and dulaglutide as “Trulicity” since 2014.

As “Mounjaro“, “Wegovy”, “Foundayo” and “Saxenda,” tirzepatide, semaglutide, orforglipron and liraglutide respectively are also licensed for weight management for people with a BMI higher than 30, or for people with a BMI higher than 27 for whom being overweight has already started to cause medical problems. (Wegovy SmPC, 2024)

Tirzepatide (Mounjaro), semaglutide (Wegovy) and orforglipron (Foundayo) have been shown to be more effective than liraglutide (Saxenda) as treatments for weight loss. Dulaglutide (Trulicity) has not been licensed in the UK as a treatment for weight loss.

Whilst on such treatment, multiple cardiometabolic risk factors improve (Wegovy STEP trials, 2022). It is therefore expected that they will reduce the risk of heart attack and stroke.

The General Medical Council instructs that medicines that do not have a product licence can be prescribed by doctors, but only under certain limited circumstances, such as if “a suitably licensed medicine that would meet the patient’s need is not available” (GMC, 2021).

For weight loss, therefore, we should only prescribe Mounjaro, Wegovy or Saxenda.

How do they work?

Tirzepatide, liraglutide, semaglutide, orforglipron and duraglutide mimic the natural hormone “glucagon-like peptide 1” (GLP-1). GLP-1, and therefore these drugs, act directly on the relevant areas of the brain to reduce the appetite. As such, they can cause weight loss and can be useful in the medical management of weight. Tirzepatide additionally mimics the hormone “glucose-dependant insulinotrophic polypeptide” (GIP).

During a meal, they also boost levels of insulin and discourage the release of glucagon, and slow down stomach emptying, all of which help to prevent glucose levels rising so high in people who have diabetes. They can therefore also be a helpful treatment for diabetes, for which they were originally developed, but they can sometimes cause temporarily low blood sugar levels. (Mehta et al., 2017)

How much weight might I lose?

Graph reproduced from Jastreboff et al., 2022, NEJM

In conjunction with lifestyle changes (reduced calorie diet and increased exercise), you might lose up to 5% of your initial weight within 12 weeks of starting either of these medicines. If you succeed in losing that much or more, we can prescribe it for longer. In trials, patients have lost on average:

22% of their initial weight on top dose tirzepatide (15mg over 72 weeks, Jastreboff et al., 2022)

ca. 18% on lower dose tirzepatide over 48 weeks (10mg, Jastreboff et al., 2022)

15% of their initial weight on semaglutide injections (over 68 weeks, Wilding et al., 2021),

13.6% of their initial weight on semaglutide 25mg tablets (over 64 weeks, Wharton et al., 2025)

8% of their initial weight on liraglutide (over 56 weeks, Pi-Sunyer et al., 2015),

5% of their initial weight on duraglutide (over 36 weeks, Frias et al., 2021).

It is important to note that some patients may lose more weight than this, and some may lose less or even none.

Will I gain weight after stopping treatment?

Graph adapted from Rubino et al., 2021, JAMA

The short answer is yes. After 20 weeks of treatment and weight loss with semaglutide, patients have been shown to regain an average weight of 6.9% over the subsequent 48 weeks (Rubino et al., 2021). This is why it is so important for patients to have access to lifestyle support (see below) to minimise any weight regain.

How are they taken?

Tirzepatide, liraglutide, semaglutide, and duraglutide are available as injections. Liraglutide is injected every day, and tirzepatide, semaglutide, and duraglutide once a week. They are started at a low dose and the dose is increased each month. They are usually injected under the skin of the stomach, upper thigh, or upper arm.

These medications are usually supplied with needles, but if not needles can be obtained inexpensively without a prescription from a pharmacist, or even from online retailers. You should store used needles in a dedicated sharps box and contact your local council to arrange disposal. (In Sefton, you can do so online).

Foundayo (orforglipron) and Wegovy (semaglutide) are available as tablets. Wegovy tablets need to be taken on an empty stomach. Foundayo and Wegovy tablets might be almost as effective as 2.4mg Wegovy injections.

Dose equivalents

based on effect on blood glucose, adapted from Whitley et al., 2023.

What are the side effects?

As with most medicines, most people tolerate tirzepatide, liraglutide, semaglutide, orforglipron and duraglutide well. The most common side effect is nausea, although other gastrointestinal symptoms can occur. Most side effects improve as your body gets used to the drug, which is partly why the dose is usually increased gradually at first.

If you have diabetes, these drugs may of course help your diabetes treatment, but it would be prudent to discuss this more fully with your prescriber.

Serious but rare side effects of tirzepatide, liraglutide, semaglutide, orforglipron and duraglutide include ileus (paralysis of the gut), pancreatitis and other gallstone problems, and depression. You should treat any constipation promptly with a laxative (to reduce the risk of developing ileus), and in any case consult your doctor if you experience abdominal pain or have concerns about your mental health.

It is not known whether tirzepatide, liraglutide, semaglutide, orforglipron and duraglutide cause a certain type of thyroid cancer in humans, but this has been observed in animal testing. These drugs should not be used by people who have either had medullary thyroid carcinoma themselves, or if a close family member has (“Important Safety Information”, www.Wegovy.com, accessed August 2024).

Are there any other options in the UK?

A reduced calorie diet can be effective on its own, but this is not easy! Diet support services have been shown to be helpful. As well as those that are commercially available, Active Lifestyles in Sefton offer “Weigh Forward”, a 12 week diet support programme, free of charge.

Orlistat is a tablet that is taken three times a day. It prevents the absorption of fat. If fat is eaten, diarrhoea can result, encouraging a low fat diet. A 3% greater weight loss than placebo over 24 weeks has been demonstrated (Jain et al., 2011). Reducing fat intake alone is probably just as effective.

Mysimba (naltrexone 8mg + bupropion 90mg) is a tablet taken twice a day: a 4.8% greater weight loss than placebo over a year has been demonstrated (Greenway et al., 2010).

How can I get tirzepatide, semaglutide or orforglipron?

Formby GP offers a full assessment, supply of Mounjaro, Wegovy or Foundayo, and ongoing lifestyle support.

• If your BMI is greater than 30, simply book a free weight loss consultation.
• If your BMI is less than 30, feel free to check with us before booking by email.
• Blood tests such as for thyroid and liver function, and diabetes (HbA1c) are also available (additional charges may apply)
• Tests for Cushing’s disease (a rare condition which can cause weight gain) we can perform for £70.50* each. It is recommended to do this test twice.

See below for our current prices. We offer an all-inclusive price which includes the following:

• The medication itself
• Needles and sharps boxes as required
• Dispensing and prescribing fees
• A copy of our “Healthy Habits Now” lifestyle advice booklet
• A one to one lifestyle induction session and ongoing lifestyle e-support with RZ Fitness. Simply share your paid invoice with the RZ Fitness team at www.FormbyGP.com/RZdiet

RZ Fitness are also happy to offer more intensive lifestyle support on request.

Here are our current prices for Mounjaro, Wegovy and Foundayo (subject to change):

Dr John Cosgrove, February 2023 (v1.0)

Updated March 2023 to include references to Trulicity & dosing of Wegovy & Ozempic (v1.1)

Updated June 2023 to include reference to Mounjaro (v1.2)

Updated October 2023 following UK licensing and limited availability of Wegovy (v1.3)

Updated February 2024 to include Mounjaro, and risk of ileus (v2.0)

Updated March 2024 to include interaction between Mounjaro and oral contraception (v2.1)

Updated August 2024 to include details of Formby GP package (v3.0)

Updated December 2024 to include details of Sefton Active Lifestyles (v3.1)

Updated August 2025 to include cardiovascular benefit, interaction with progesterone,
dose equivalents, September 2025 prices (v3.2)

Updated June-Sept 2026 to include Wegovy and Foundayo tablets (v4.0 draft)

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