How to inject Mounjaro: A step-by-step guide

Before you inject Mounjaro, you need to choose an injection site. Mounjaro is injected just under the skin of your:

• stomach
• upper thigh
• upper arm – you should get help from someone else if you inject here, as it can be difficult to inject yourself at the correct angle (90°)

You can inject in the same area each week, such as your upper thigh, but you must rotate the injection site within that area, leaving at least a finger width between your last injection site and the next.

If you find you’re struggling to remember injection sites, try using a marker to dot your injection site before you take your weekly injection. Take a picture, so you can check each week where your next injection should be. You can also divide the area into 4, and rotate in a circle, writing down on your calendar or notes which part of the area you last injected.

Alternatively, you can change the injection site location each week. For example, you might inject in your stomach in week 1, your upper thigh in week 2, your upper arm in week 3, and so on.

With your first few injections, you’ll be able to find what works for you.

1. If injecting Mounjaro on your own, choose either the abdomen or upper legs. If someone is helping you, they can inject into your upper arm or one of the other injection sites.
2. Split the injection site into 2 sections on each side of your body (see the image following this section for an idea of what this looks like). Rotate the site each week so you’ll only be injecting into the same area at least once every 4 weeks.
3. When injecting into the stomach, always leave a 5cm gap from your belly button (navel).
4. Always inject at least 1 finger width away from your last injection.

Does the injection site impact side effects?

It might. A study into the side effects of Mounjaro 5mg when injected into the 3 different injection sites found that gastrointestinal side effects (those that affect the stomach and digestive system) happened less often when patients were injected in their thigh.

Some of the results are shown in this table:

In the same study, it was also found that appetite reduction was strongest when Mounjaro was injected into the stomach (24%), then in the upper arm (13%), and then the thigh (6%). So, even though the thigh may reduce gastrointestinal side effects, it may also result in less appetite suppression. This does not necessarily mean less weight loss, though, as long as you stick to your diet and exercise plan.

There has always been debate about where certain injections, such as weight loss injections or insulin, can have different effects if injected in different places. Many people notice that 1 injection site works best for them, and if you have side effects, it could even be worth switching injection sites to see if this helps. But remember: what works best for you may not be what works for someone else.

Before injecting Mounjaro, there are a few things you need to do to prepare.

If it is your first time using Mounjaro and you are apprehensive about injecting, this is very common. Follow our guidance on our dedicated section on this page ‘Dealing with injection anxiety’.

Mounjaro will be delivered in a box containing:

• a pre-filled injection pen that includes 4 doses, 1 per week
• a patient information leaflet
• an instruction leaflet on how to use Mounjaro

It is important to inject Mounjaro on the same day each week because it:

• ensures a consistent amount of the medication remains in your body
• helps your body get used to the medication, reducing the risk of side effects

When you are ready to inject Mounjaro:

1. Wash your hands with warm, soapy water and dry them thoroughly.
2. Check the correct dosage is displayed on the original packaging and that it is within date.
3. Take the pen out of the box and inspect for any damage.
4. Remove the protective cap from the pen and check the dosage window to make sure the liquid is clear and free from any debris or particles – if the solution is frozen, do not use it.
5. Get a new needle ready close-by, and make sure it’s not unsealed, bent, or damaged in any way.
6. Wait 30 minutes to allow your cold Mounjaro pen to reach a warmer temperature*, if you choose to refrigerate your pens. If you keep your pens out of the fridge, you are ready to inject.

*Some people prefer to keep Mounjaro out of the fridge because injecting a cold liquid can make the injection sting more. You can take your pen out of the fridge around 30 minutes before your injection, so it will not be as cold. Doing this might help make the injection more comfortable for you.

As 4 doses cover a 28-day period, it does not matter whether you store an opened Mounjaro pen in or out of the fridge as long as the temperature conditions are met – the pen should be stored in its original packaging and in temperatures up to 30°C for 30 days. So, if leaving it out of the fridge is better for your injection experience, it’s safe to do this.

What to know about needles and sharps bins

Needles:

You must use the correct needles with a Mounjaro pen. Usually, these will be supplied with your medication, but if you need more for any reason, speak to your prescriber or a local pharmacy. The most common types of needles used for Mounjaro pens are 4mm or 5mm in length, and their gauge (the diameter of the needle) is 31 or 32G. When compared to the average length of a needle used for things like vaccinations (25 to 38mm), 4mm is very short.

The gauge of a needle is how thick it is, and the higher the number, the thinner the needle. Mounjaro needles are very small and thin, meant to make the injection experience as comfortable as possible. They’re also short to make sure the injection is given in the correct area (the fat at the top of your skin) rather than going in too deep and being injected into the muscle. This means there is very little chance of injecting into the wrong place, as long as you stick to the 3 injection sites provided by the manufacturer.

Here's an example of the needle that you will attach to the top of your pen, which will be individually wrapped:

All needles should be disposed of in a sharps bin.

Sharps bins:

If you’re using Mounjaro, you must have a sharps bin to make sure you’re disposing of needles safely. They should not go in a normal bin or be reused. You can get a sharps bin from Asda Online Doctor if you are a patient with us, otherwise speak to your prescriber, GP, local council, or local pharmacy.

When your sharps bin is full, or if you’ve stopped treatment, you can contact your local Council to collect and dispose of your finished sharps bin. You can also ask your local pharmacy, some also provide this service. Councils have different provisions, and with some, you may not have several collections in a year, so make sure you’re only disposing of it once it's full.

The Mounjaro ‘KwikPen’ is a single-patient-use pen that contains 4 fixed doses, with 1 dose injected each week. That means 1 pen provides 4 weeks of treatment. Once all 4 doses have been used, you can throw the pen away.

Once you have performed steps 1 to 4 in the ‘When you are ready to inject Mounjaro’ section, you are ready to administer your medication.

First, you will need to prime your pen:

1. Wipe the inner red seal with a swab.

2. Select a new pen needle – always use a new needle for each injection and make sure it’s not broken or bent in any way – and remove the paper tab from the outer needle shield.

3. Push the capped needle straight onto the pen and turn it clockwise until it’s tightly secured on the pen.

4. Remove the outer needle shield and place it to one side – you will need this later – then remove the inner needle shield and throw it in your household rubbish bin.

5. Slowly turn the dose knob until you hear 2 clicks and the extended line is displayed in the dose window. This is the prime position. If you need to, you can turn the dose knob in either direction until it lines up to the dose indicator.

6. Holding your pen so the needle is pointing up in the air, gently tap the cartridge holder to send any air bubbles to the top.

7. Release some medicine into the air by pushing the dose knob until it stops, then slowly count to 5. The ‘0’ icon should be displayed in the dose window – do not inject it into your body. If a small amount of medication is released from the tip of the pen needle, your pen is primed.

How to inject Mounjaro:

8. Choose your injection site. You do need to squeeze or pinch the area of skin you want to inject. Although this is common if you’re injecting things like insulin, Mounjaro has a very small needle and is used on places with subcutaneous fat, which means you do not need to pinch your skin for the injection to go in the right place. However, even if not necessary, there’s no harm in doing it if you feel more comfortable injecting this way or if you find it helps with pain.

9. Turn the dose knob until it stops and the ‘1’ icon is displayed in the dose window – this represents one 0.6ml dose.

10. Insert the needle into the skin at your chosen injection site, at a 90° angle. Make sure you or the person doing the injection can see the dose counter. Injecting at a 90° angle can help the injection go in straight, which may reduce pain as the pointiest part of the needle is directed straight at your skin.

11. Push the dose knob until it stops, then slowly count to 5 while still holding the dose knob in. Check the ‘0’ icon is shown in the dose window before removing the needle from your skin.

12. Pull the needle from your skin. It is normal to see a small drop of medicine at the end of the needle after removal, it will not affect your treatment.

After the injection is done:

13. Carefully replace the outer needle shield onto the needle and discard it in your sharps bin.

14. Replace the pen cap and store your pen away until your next dose.

Some people may not want to use Mounjaro because they need to self-inject. While Mounjaro can be very effective for your weight loss journey, pushing past a fear of needles can be difficult.

“Managing injection anxiety can help make your experience with Mounjaro more comfortable. If you want to use Mounjaro, here are some tips to help make injecting easier:

• get someone to help you – not doing the injection yourself can help massively with needle phobia, and this way, you can focus on something else to take your mind off it
• use distraction methods – during the injection, find something to do that will help calm your mind, whether it’s speaking to someone, watching your favourite show, or having something to fiddle with
• try breathing techniques – focusing on your breathing can help calm anxiety, and can also be a good distraction technique, such as counting your breaths in and out
• use numbing spray, and other methods that will make the injection more comfortable – you can get numbing sprays and creams at your local pharmacy, ice pack the injection area beforehand to make it numb, and keep your injections out of the fridge to reduce the sting

If you do not feel confident injecting Mounjaro, make sure to read carefully through the patient information leaflet and speak to your doctor. A pharmacist or doctor may also be able to give you a demonstration.” – Dr Kathryn Basford, Medical Editor.

After you have injected Mounjaro, you might notice a small amount of blood where the needle entered your skin. This is usually nothing to worry about and you should lightly press a small piece of gauze or cotton wool on the injection site.

You may also notice a small amount of bruising at the injection site, this should fade away within a few days.

How do I reduce pain during and after injecting Mounjaro?

You can reduce pain and irritation during and after injecting Mounjaro by:

• taking an antihistamine tablet
• applying an over-the-counter antihistamine cream to the affected area – a pharmacist may help you
• changing your injection site weekly
• cleaning the skin before injecting Mounjaro with a swab
• applying an ice pack to the injection site to numb the area and prevent irritation before injecting your medication
• taking over-the-counter painkillers if you feel sore after injecting
• applying a cold compress to reduce swelling after the injection
• injecting at a 90° angle – this will make sure the needle point goes directly into your skin, rather than at a 45° angle, which will cause more friction against the skin as the needle is inserted

Some people may experience a reaction to Mounjaro at the site where they inserted the needle.

Clinical trials show that Mounjaro injection site reactions were reported in 3.2% of patients compared to 1.7% of patients given a placebo.

Up to 1 in 10 people may experience hypersensitivity reactions when using Mounjaro or other weight loss injections. Common reactions include:

• skin rashes
• itching
• eczema
• swelling
• redness

If you experience any of these symptoms, let your doctor know. They may suggest trying a lower dose, changing the injection site, or using a topical over-the-counter cream to relieve any irritation.

It should not be very painful to inject Mounjaro – any severe irritation, swelling, or redness should be seen by a doctor straight away. This could be a sign of an allergic reaction.

Sometimes, Mounjaro pens can malfunction and not work properly. Some common causes of Mounjaro pen malfunctions include a problem with the needle, such as it being bent, or the pen becoming jammed. If this happens, check that the needle is attached properly, is not bent or damaged, and follow the instructions to prime your pen. If this does not work, speak to your prescriber, as you may need a new pen.

You should not use your pen if it’s leaking liquid or if the medication is not coming out despite following the instructions in your user manual.