What is Tirzepatide and is it Safe for Weight Loss?

Dr Babak Ashrafi

Medically reviewed by

Dr Babak Ashrafi

Last reviewed: 26 Feb 2024

Tirzepatide weight loss treatment is injected once a week to help you lose weight as part of a wider diet and exercise programme. It’s found under the brand name Mounjaro.

Tirzepatide is the first dual-action medication created in the drug classes of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. It works by mimicking these hormones to control blood sugar levels, but research shows it also induces weight loss.

Tirzepatide is one of the few medications licensed in the UK for weight loss.

2 Mounjaro KwikPens Doses with 2.5 mg and 5 mg of Tirzepatide

Key takeaways

  • Tirzepatide has recently been approved as a weight loss medication in the UK and is now available to buy on private prescription.

  • Tirzepatide for weight loss is found under the brand name Mounjaro.

  • The active ingredient tirzepatide mimics 2 hormones in your body that are responsible for regulating appetite, cravings, blood sugar and how your body breaks down fats and sugars.

  • Taking tirzepatide alongside a diet and exercise programme has been proven to help people lose weight.

What class of drug is tirzepatide?

Tirzepatide’s drug class is both a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. GIP and GLP-1 are hormones that occur naturally in your body. Tirzepatide works by imitating these 2 hormones to lower your blood sugar levels and appetite.

You may hear tirzepatide being referred to as a dual receptor agonist. It is the first drug in this class of medications to be approved and released for type 2 diabetes and weight management. Mounjaro is the brand name for tirzepatide for weight loss.

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What is tirzepatide used for?

Tirzepatide works by reducing your appetite and slowing down the movement of food from the stomach to the small intestine. This process helps to leave you feeling fuller for longer, making it easier to reduce your calorie intake. For this reason, tirzepatide has been released as a medication for weight loss.

Tirzepatide is also approved for the treatment of type 2 diabetes. Tirzepatide lowers blood sugar levels by increasing the production of insulin and lowering the amount of sugar your liver makes.

Is tirzepatide available in the UK?

Yes, tirzepatide (Mounjaro) is available to buy through a private prescription. The Medicines and Healthcare products Regulatory Agency (MHRA) approved Mounjaro (tirzepatide) for weight loss and weight management for people aged 18 and over in November 2023. The NHS is aiming to make it available for NHS prescription soon.

Tirzepatide was also approved by the National Institute for Health and Care Excellence (NICE) for treating type 2 diabetes in England and Wales in October 2023.

Are tirzepatide injections safe?

Dr Babak Ashrafi

Yes, tirzepatide is considered safe for weight loss if you meet the acceptance criteria, such as a body mass index (BMI) of 30 kg/m2, or a BMI higher than 27 kg/m2 and weight-related health problems. However it will not be suitable for everyone, so your doctor will help decide if it is the right course of treatment for you based on your medical history.” – Dr Babak Ashrafi, Clinical Lead for Service Expansion.

What does tirzepatide do in the body?

Tirzepatide is a GIP and GLP-1 receptor agonist. This means it can activate the receptors for both GIP and GLP-1, both of which affect the parts of the brain known for controlling appetite.

Tirzepatide’s mechanism of action is to:

  • lower food intake
  • stimulate the release of insulin from the pancreas
  • slow down the digestion process
  • reduce the production of glucagon by the liver

Together these mechanisms work to reduce appetite and cravings, improving weight loss results when following a diet plan.

How does tirzepatide work for weight loss?

Tirzepatide for weight loss works by reducing your appetite and hunger levels, making it easier to eat less. It also improves how your body breaks down fat and sugar from your diet. These effects work alongside other lifestyle interventions, such as positive diet changes and an increase in physical exercise.

How successful is tirzepatide for weight loss?

The MHRA's recommendation for tirzepatide to be prescribed for weight loss in obese and overweight patients with and without diabetes was based on the results of 2 randomised, double-blind, placebo-controlled clinical trials.

In both studies, SURMOUNT-1 and SURMOUNT-2, patients who received tirzepatide treatment showed significant weight loss compared to those treated with placebo. In the SURMOUNT-1 study involving 2,539 obese or overweight patients with one weight related complication, more than 96% of people who received 15mg of tirzepatide lost at least 5% of their body weight after 72 weeks of treatment.

How much weight can you lose on tirzepatide?

How much weight can be lost on tirzepatide will depend on the individual. Obese or overweight individuals with one weight-related complication (which was not type 2 diabetes) receiving 10mg of tirzepatide once weekly, for 72 weeks, lost on average 21.4% of their body weight. Those receiving 15 mg once weekly lost 22.5%.

Obese or overweight individuals with type 2 diabetes lost on average 13.4% on 10mg and 15.7% on 15mg over 72 weeks.

Can I get tirzepatide without diabetes?

Yes. Although tirzepatide was first licensed for diabetes, you don’t have to be diabetic to receive tirzepatide (Mounjaro) for weight loss.

Tirzepatide for weight loss is indicated for adults who have a:

Tirzepatide vs semaglutide vs dulaglutide

Tirzepatide (Mounjaro), semaglutide (Ozempic) and dulaglutide (Trulicity) are all diabetic injections and have been shown to induce weight loss, though Mounjaro is now licensed for weight loss without diabetes too. In clinical trials, both tirzepatide and semaglutide outperformed dulaglutide for both blood sugar control and weight loss.

Wegovy also contains semaglutide but is approved for weight loss rather than type 2 diabetes. Saxenda is another weight loss injection approved in the UK but is currently unavailable, so many people are switching from Saxenda to Wegovy.

Comparison table of Tirzepatide vs Semaglutide vs Dulaglutide.

How to take tirzepatide

Tirzepatide is designed to be easy to use and is supplied in a multi-dose pen (kwikpen). You should use tirzepatide for weight loss exactly as your doctor has told you. Before you start using the tirzepatide injection you should pick which day of the week works best for you.

It is a once-weekly dose and you should inject it on the same day each week. You may find it helpful to set a reminder on your phone so you don’t forget to take it on your chosen day.

Your tirzepatide dosage is increased slowly to reduce side effects. The starting dose for tirzepatide is 2.5 mg. After 4 weeks this will increase to 5 mg once per week. The dose can then be increased by 2.5 mg every 4 weeks. The maximum dose is 15 mg injected once a week.

Here are the general instructions for using the tirzepatide multi-dose injection pen:

  • Choose your injection site. Your doctor can help you choose but it should be injected into your stomach or thighs. Rotate the injection site each week or use the right then left side of your body to reduce soreness.
  • Use a new needle for each injection and make sure it’s not unsealed, bent, or damaged. If it is, you should use a new needle.
  • The liquid inside your pen should also be clear and colourless, or have a slight yellow tinge. Otherwise, it should not be used and you should speak to your doctor or supplier.
  • Once ready, inject your dose into the skin (never a muscle or vein). Press and hold the button for no more than 10 seconds.
  • When you have finished you should discard the used needle in your sharps container.

Who can take tirzepatide?

Tirzepatide, under the brand name Mounjaro, is authorised for weight loss in adults who have a:

  • BMI of 30 kg/m2 or above or a
  • BMI of between 27 and 30 kg/m2 and have a weight-related health problem

Tirzepatide is also recommended for people who have unmanaged blood sugar and type 2 diabetes, alongside diet and exercise changes. It is generally prescribed when other diabetes treatments, like metformin, have no effect.

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When is the best time to take tirzepatide?

Tirzepatide can be injected at any time of day, with or without food. You should choose a day and time that is most convenient for you.

How much does tirzepatide cost?

Tirzepatide prices will vary depending on where you get your prescription. Prices for Mounjaro at ASDA Online Doctor start at £184.00 for one month’s supply. If you get a prescription from the NHS in England, you’ll likely need to pay the current prescription charge.

Tirzepatide side effects

The side effects of tirzepatide include:

Very common

  • feeling sick (nausea)
  • diarrhoea
  • constipation
  • low blood sugar, if used alongside other diabetes treatments


  • being sick (vomiting)
  • reduced appetite
  • indigestion
  • tummy pain
  • low blood pressure
  • bloating
  • dizziness
  • hair loss
  • reflux or heartburn
  • feeling tired
  • fast pulse
  • a decrease in appetite

Uncommon side effects

  • gallstones
  • pain at the injection site
  • infection of the gallbladder
  • gastroparesis
  • an inflamed pancreas (acute pancreatitis) – speak to your doctor if you get severe stomach or lower back pain
  • an increased level of calcitonin (a hormone that helps to metabolise calcium) in the bloodstream

If you get tirzepatide side effects, speak to your doctor if they don’t go away or bother you too much.

Tirzepatide contraindications

Tirzepatide is not suitable for everyone and you should only take it if your doctor prescribes it to you.

You should only use tirzepatide for weight loss if you meet the specific weight criteria to use it. Tirzepatide injection may not be suitable for you if you have:

  • a history of pancreatitis
  • a severe gastrointestinal condition

You should not use tirzepatide if you are allergic to any of its ingredients. Tirzepatide injection is also not suitable if you are pregnant or breastfeeding.

If you are taking any other prescription, over-the-counter, or herbal remedies, you should tell your doctor before using tirzepatide for weight loss because it may interact with other medicines. You should also let your doctor know if you are taking any other diabetic medications.

What are the warnings on tirzepatide?

You shouldn’t use tirzepatide if you have a history of pancreatitis because the condition has developed in some people treated with GLP-1 receptor agonists. Some people also develop gallbladder stones during treatment, so you should tell your doctor if you have a history of these.

If you are allergic to any of the ingredients in tirzepatide injections, this treatment will not be suitable for you. In allergic individuals, tirzepatide can cause serious complications.

If you are worried about using tirzepatide for weight loss, speak to your doctor about your concerns beforehand.

Who cannot take tirzepatide?

You cannot take tirzepatide if you are:

  • under 18
  • allergic to any of the ingredients in tirzepatide, including the active and non-active ingredients
  • pregnant or breastfeeding

Can you buy tirzepatide online in the UK?

Tirzepatide has been approved for weight loss in the UK under the name Mounjaro. You can buy tirzepatide online from registered online doctor services like Asda Online Doctor by filling in a short medical form about your health, medications, and weight. A doctor can approve your treatment if suitable, which will be delivered to you in discreet packaging.

Is tirzepatide prescription-only?

Yes, tirzepatide is prescription-only which means a doctor must prescribe it to you for weight loss. Over-the-counter tirzepatide does not exist, so be wary of websites offering you tirzepatide or Mounjaro without a prescription, as this is illegal.

Is tirzepatide available on the NHS for weight loss?

Tirzepatide on the NHS will be available soon.


Tirzepatide is a type 2 diabetic treatment that has recently been approved for weight loss in the UK under the brand name Mounjaro. You can get tirzepatide for weight loss if you meet certain criteria, such as a BMI over 27 kg/m2 and a weight-related medical condition, or a BMI over 30 kg/m2. You can get tirzepatide for type 2 diabetes from your GP, but only if you have unregulated blood sugar levels.

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Frequently asked questions

What is another name for tirzepatide?

Tirzepatide is the generic name for the diabetes and weight loss medication, Mounjaro. Tirzepatide brands include Mounjaro (tirzepatide) and Zepbound (available in the US). So, Mounjaro is the tirzepatide trade name.

Tirzepatide is only available as an injectable medicine, so you cannot get a tirzepatide tablet under another name.

In what countries is tirzepatide available?

Tirzepatide for weight loss is available in the UK. Tirzepatide is available in the USA and European Union for the treatment of type 2 diabetes.

How can I get tirzepatide?

You will need a prescription from a doctor to get tirzepatide. To use tirzepatide for weight loss, you will need to fit some specific criteria. You can get it in a pharmacy with a prescription, or through an online pharmacy or doctor service that can provide a prescription.

What is the best injection for weight loss?

The best injection for weight loss will depend on your circumstances. There are various options available with different active ingredients, different effectiveness rates, and varying side effects. To find the best weight loss injection for you, you should discuss your circumstances with your doctor.

Does tirzepatide cause hair loss?

Hair loss is listed as a common side effect in the Mounjaro patient information leaflet.

A 2022 study found that some people who used the branded tirzepatide injection, Mounjaro, reported hair loss. This occurred in 4.9 - 5.7% of people using 5 - 15 mg doses compared to 0.9% of people who were given a placebo. This is usually temporary but you can speak to your doctor if you have concerns.

What BMI is required for tirzepatide?

To be eligible for tirzepatide for weight loss, you will need a:

  • BMI of 30 kg/m2 or above or a
  • BMI between 27 and 30 kg/m2 and a weight-related health problem (prediabetes, high cholesterol, high blood pressure)
Medically reviewed by:
Dr Babak Ashrafi Clinical Lead for Service Expansion

Babak studied medicine at King’s College London and graduated in 2003, having also gained a bachelor’s degree in Physiology during his time there. He completed his general practice (GP) training in East London, where he worked for a number of years as a partner at a large inner-city GP practice. He completed the Royal College of GPs membership exam in 2007.

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Last reviewed: 26 Feb 2024

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