Mounjaro and tirzepatide: your 5-minute guide

Mounjaro (tirzepatide) is a weight loss and diabetes drug. Read our 5-minute guide to learn the key facts.



When was Mounjaro approved in the UK as a weight loss medication?

In November 2023, Mounjaro was approved by the Medicines and Healthcare products Regulatory Agency (MHRA) for use in the UK for weight loss and management. It is only available on prescription from a doctor and can only be prescribed to adults aged 18 and over.

At the time of writing, Mounjaro is unavailable on the NHS as a weight loss treatment – but that may soon change.

Who has it been approved for?

The MHRA has authorised Mounjaro for people who meet the following criteria:

• Adults with obesity (with a BMI of 30 or more)
• Adults who are overweight (with a BMI between 27 and 29) and have weight-related health issues – these can include pre-diabetes, high blood pressure, high cholesterol and heart problems

The medicine is to be used together with a reduced-calorie diet and increased physical activity. 

At SemaPen, we have been able to offer Wegovy – another injectable weight loss medication – since it was approved for use in the UK in September 2021.

However, we have since launched a Mounjaro programme, too. This is available to patients who meet the MHRA's BMI guidelines and several other criteria. 

You can find out instantly if you're eligible by taking our online consultation.

How does Mounjaro (tirzepatide) help you lose weight?

Mounjaro works by mimicking two natural hormones in the body. These hormones are responsible for controlling digestion, blood sugar and satiety (the feeling of fullness), among other things.

Mounjaro has similar effects:

• It regulates blood sugar levels
• It helps control hunger and food cravings
• It gives you a 'full-up' feeling
• It slows digestion

In other words, Mounjaro isn't a magic wand that makes fat disappear. But it can help you lose weight by making you feel full and giving you more control over your eating habits.

What about side effects?

Like all medications, Mounjaro can cause unwanted side effects.

The most common side effects experienced by Mounjaro patients are nausea and stomach upsets (including diarrhoea), as well as vomiting and tummy pain.

These side effects are fairly common with incretin memetics like Wegovy and Mounjaro. However, they tend to happen less with Mounjaro than Wegovy.

For most patients, the side effects aren't too bad and can be treated effectively with home remedies. Many find they experience fewer or less pronounced side effects as they continue the treatment. 

However, when you step up to a higher dose, the side effects can worsen again for a short time as your body adjusts.

Mounjaro can also make the contraceptive pill less effective. It would be a good idea to use a different form of contraception during your weight loss program.

A small number of Mounjaro patients have noticed their hair thinning or more hair than usual coming out when brushing. This isn't directly caused by the medication. Instead, it's caused by the rapid weight loss affecting your body's nutritional balance. For most people, the hair thinning or mild hair loss gets better as they continue the treatment and take the recommended supplements.

For more information on side effects, including potentially serious side effects, read our expert guide.

What is a Mounjaro KwikPen?

Mounjaro comes in a KwikPen. This is a medical device that's about the same size and shape as a felt-tip marker pen. It's designed to make it easy to inject yourself at home.

The pen is already filled with enough liquid medication for four weeks. You should take one injection per week on the same day each week.

The starting dose is 2.5mg per week. After your first month, you'll step up to a new pen with a 5mg dose. The dose increases each month until it reaches 15mg from month six onwards.

We increase the dose gradually because it takes time for your body to adjust to the medication. But you don't need to worry about remembering to order the right dose. When you subscribe to the SemaPen programme, we'll automatically send you the right pen at the right time.

How do I take Mounjaro?

Every dose requires a new sterile needle. These are provided separately. They come fixed in a screw-on plastic head with a cap covering the sharp end. The needle isn't very long because you'll be injecting the medication just below the surface of the skin into the subcutaneous fat layer.

This plastic injection head easily screws onto the end of the pen. You then simply remove the cap when you're ready to inject.

First, you need to prime the pen. Click the dial until the dose window shows an extended line. Now, hold the pen upright and squirt a little liquid out by pressing on the dose knob. This removes air from the cartridge and ensures the pen is working correctly.

If everything looks good, you can prepare your dose. The good news is that the pen does this for you. Simply twist the dose knob until it clicks. You'll see the dosage number appear in the little viewing window on the side. 

When you're ready to inject, just pinch a handful of skin into a fold between your thumb and forefinger. Now, push the needle in just under the skin and press the dose knob down as far as it will go.

The medication needs to go straight into the subcutaneous fat layer under the skin. Good sites to choose are the fronts of your thighs and the soft part of your belly (at least 5cm away from the belly button).

Most patients get used to injecting themselves quite quickly. However, if you've never done it before, you might feel a little nervous. Our step-by-step guide will help and, of course, your SemaPen medical team will always be available to answer questions and give practical advice.

Are you interested in starting Mounjaro treatment? Find out how much Mounjaro costs per month through SemaPen – or visit our programme page to learn more about how the SemaPen subscription works.

Sources

1. Jastreboff, A.M. et al. (2022) "Tirzepatide Once Weekly for the Treatment of Obesity" New England Journal of Medicine, 387(3) https://doi.org/10.1056/NEJMoa2206038

2. Abdullah, A. et al. (2010) "The magnitude of association between overweight and obesity and the risk of diabetes: A meta-analysis of prospective cohort studies" Diabetes Research and Clinical Practice, 89(3) https://doi.org/10.1016/j.diabres.2010.04.012

3. https://www.healio.com/news/endocrinology/20211005/weight-loss-of-15-should-be-primary-goal-for-most-people-with-type-2-diabetes