Where to Inject Mounjaro®: Best Sites, Rotation, and Technique

If you’re starting Mounjaro® as a new treatment and you’re worried about injecting yourself for the first time, that’s understandable. Choosing where to inject may feel daunting, especially if you’re worried about getting it wrong. As long as you stick to the suggested injection sites, you should be fine - the stomach, thighs or upper arm.

Apart from using the right injection sites, it’s important to rotate the site, so you aren’t injecting in the same place each week. As long as you’re injecting in the right place with the right technique and rotating injection sites, you can be confident you’re using Mounjaro® correctly. This guide covers all three of these factors, as well as common questions and useful tips.

The Three Approved Injection Sites

You can inject Mounjaro® in 1 of 3 places: the stomach, the thighs, or the upper arm.* There isn’t one site that is recommended over the others or one that everyone chooses to use. The right site for you is the one you feel most comfortable using.

You can continue using the same site if it works for you, but you need to rotate the place you inject each week – this means leaving 2 to 3cm (about a finger’s width) between injections. You don’t have to stay with one injection site either. You can change them if it suits you.

You should also make sure that no matter which site you choose, you do not inject into bruised, sore, red or hardened skin.

Some practical considerations for choosing a site can include:

• How easily you can see and reach your injection site – you may not be able to comfortably see or reach your thighs, in which case your stomach might be better for self-injecting, and if you can’t easily self-inject, or you want to inject in your upper arms, it’s best to have someone do it for you

• Whether your injection site is likely to be bumped – for example, if you have someone inject your arm and then ride a crowded bus, you could find your injection site is nudged or bumped repeatedly, causing irritation

• Whether your injection site is likely to be rubbed by your clothes – a skirt or loose T-shirt may make it less likely for your injection site to be rubbed and irritated, whereas tight-fitting trousers, shirts or jackets could rub and irritate your injection site

*European Medicines Agency. (2026). Mounjaro, INN-tirzepatide.

Injecting into the stomach

The stomach (the abdomen) can be a good choice because it’s easy to see and reach for most people. You need to choose the right area and leave at least 5cm (2 finger widths) between your belly button and where you inject. Try to choose an area that has more fat and avoid bonier areas like your hip bones.

Injecting into the thigh

Like with the stomach, the thigh may be a convenient place to self-inject if you can easily reach it. You don’t have to stick with just 1 thigh and you can switch between them if you like. It’s best to use the upper and outer parts of the thigh and avoid injecting into the inner thigh. You can inject sitting down or standing up – whichever works for you.

Injecting into the upper arm

This injection site may be less suitable for self-injecting and it may be easier with someone else injecting your Mounjaro® for you. The reason for this is because it’s awkward to use only one arm to reach around and inject into the upper arm on the other side. However, if you do have someone to help you, this can be considered alongside the other injection site options.

Choosing a site around your cycle

It may help to adjust your injection site to where you are in your period cycle. For example, if you get period-related bloating then your stomach may feel more swollen, tender or uncomfortable. If this is the case for you, it may help to use an alternative injection site, like the thigh.

Don’t feel that you need to use your normal injection site if it’s not right for you. It’s best to change sites where appropriate. One thing to remember is that if the thighs aren’t suitable for you and you need to avoid injecting in your stomach during your period, you may need someone to help you inject in your upper arm instead.

Why and how to rotate injection sites

Rotating injection sites is important because injecting Mounjaro® in the exact same place repeatedly can cause something called ‘lipohypertrophy’ – when the fatty tissue under the skin becomes thicker or lumpy*. The area can then appear firmer or look raised.

There are other reasons to rotate injection sites as well, including damage to your skin and your medication not being absorbed properly. It can even lead to infection and scarring in some cases.⁺

Avoiding the side effects of injecting in the same spot is straightforward – you just need to make sure you use a different spot each week that is at least 2 to 3cm (a finger’s width) from the previous spot. It is recommended that you wait at least 3 to 4 weeks before injecting in the same spot again.

A simple rotation schedule may look like this:

1. First injection, Spot A

2. Second injection, at least 2 to 3cm from Spot A – Spot B

3. Third injection, at least 2 to 3cm from Spots A and B – Spot C

4. Fourth injection, return to Spot A and begin the schedule again

If you’re having trouble remembering where you injected each week, an alternative rotation schedule could be:

• First injection, left side of stomach

• Second injection, right side of stomach

• Third injection, left thigh

• Fourth injection, right thigh – then begin again with the left stomach next week

If you have any trouble remembering injection sites or your rotation schedule, write it down or use reminders in a calendar app on your phone.

*Mader JK, et al. (2025). Risk factors for lipohypertrophy in people with insulin-treated diabetes: a systematic meta-analysis.

⁺Frid AH et al. (2016). Worldwide Injection Technique Questionnaire Study: Injecting Complications and the Role of the Professional.

How to Inject Mounjaro®

Once you’ve chosen your preferred injection site then you can get ready to inject yourself. Your Mounjaro will come with detailed how-to-use instructions inside the medication packaging. You can also refer to this guide as well, but it is not intended to replace the manufacturer’s instructions.

Step-by-Step Injection Technique

1. Cleaning the injection site

• Wash your hands

• Choose the spot to inject in, making sure it isn’t bruised, red, sore or hardened

• Wipe the skin with an alcohol swab included in your medication packaging

• Let the skin dry completely before injecting

2. Preparing the pen

• Pull the pen cap off

• Check your pen isn’t expired or damaged and that the liquid is not cloudy or discoloured

• Wipe the red inner seal with another alcohol swab

• Pull the paper tab off of a new needle and screw it onto the pen

• Pull the outer needle cap off and keep it

• Pull the inner needle cap off and throw it away

• Turn the dose knob until you hear 2 clicks and you can see the extended line against the indicator

• Hold your pen up and tap the cartridge to move air bubbles to the top

• Release some medication by pushing the dose knob button and count to 5 slowly until it stops and ‘0’ is shown

3. Injecting: angle, hold time, and removal

• Turn the knob until it reaches ‘1’

• Insert the needle into your skin – try to insert it at a 90° angle (a right angle)

• Inject the medication by pushing the dose knob and counting to 5 slowly until ‘0’ is shown again

• Pull the needle out of your skin

4. Disposing of the needle safely

• Put the outer cap back on the needle, unscrew it and put it in the sharps bin

• Put the pen cap back on and put your injection pen away

For specific advice on injecting at your chosen injection site, see the section on The Three Approved Injection Sites.

Does the Injection Site Affect How Well Mounjaro® Works?

No. There is no real difference between injection sites in terms of how well your medication is absorbed.* Mounjaro® can be injected into the stomach, thighs or upper arm and the effect is the same no matter which is chosen.

Which one works best for you depends on which is more convenient for you and which you feel most comfortable using. It doesn’t have an effect on how well your Mounjaro® works. The only thing that can negatively affect how well Mounjaro® works is if you use the exact same injection spot every week – this can stop the medication being absorbed properly.

*Eli Lilly and Company Limited. (2026). Mounjaro® Summary of Product Characteristics (SmPC). 

Tips for a More Comfortable Injection

There are a few things you could try to help make your Mounjaro® injections as easy and comfortable as possible for yourself, including:

• Taking the pen out of the fridge before use – if you take your pen out of the fridge 15 to 30 minutes before using it, it can warm up a bit, which may make it less likely to sting, although it should not be allowed to go above 30°C and should not be heated up or microwaved

• Choose healthy skin to inject into – avoid injecting into damages, red, hardened or sore skin

• Wear loose-fitting clothing – this can help prevent clothes rubbing against the injection site and causing irritation

• Use a cool pack afterwards – using a cool pack wrapped in a cloth, or a substitute like a bag of frozen peas, and holding it against the skin after injecting may help soothe any pain or irritation

• Rotate your injection spot – remember not to inject in the same place as last week to avoid additional side effects

• Take your time – you don’t need to rush when injecting, so wait until you’re clear on what to do and feeling comfortable and confident

What to Do if You Inject Incorrectly

If you think you’ve made a mistake with your injection, don’t panic. What you should do depends on what went wrong. Make sure you know what to do before attempting another injection.

If you think you didn't receive the full dose

If you notice your dose window hasn’t reached ‘0’ after you’ve removed your needle, don’t start again or try to repeat your injection. Instead, talk to a healthcare professional. If you’re receiving treatment from Hers, you can contact a clinician through the Hers App.

If some medicine appeared on your skin

A small drop of medication on your skin after injecting is normal and usually isn’t something to be worried about. If your dose indicator reached ‘0’ before you removed your needle, you should have received your full dose, even if some remains on your skin.

If you injected into the wrong area

If you accidentally injected yourself outside the 3 recommended injection sites of the stomach, thighs or upper arms, do not take another injection to make up for it. Get in touch with a Hers clinician, especially if you think your medication may not have been injected under the skin properly.

If you accidentally injected twice

If you’ve accidentally given yourself multiple injections, you should get medical help right away. An overdose of Mounjaro® can cause stomach-related side effects like feeling sick, throwing up and diarrhoea, which can lead to dehydration. Check the patient information leaflet for signs of serious side effects and contact 111 or 999 if necessary.

If you’re not sure what went wrong

Avoid taking another injection and contact a Hers clinician. Explain what happened to them and follow their advice. Checking against the step-by-step instructions included by the manufacturer may help.

Does the Mounjaro® Injection Hurt?

It’s normal to worry about whether self-injecting Mounjaro® will be painful, especially if you are worried about needles or you’ve had painful injections in the past. For most people, the Mounjaro® injection causes very brief and mild pain, like a small pinch or sting – sometimes compared to a mosquito bite.

The Mounjaro® KwikPen® is an injection to insert medication below the skin. It doesn’t inject into the muscles or veins like some injections, such as vaccinations and blood tests.

Is it normal for the injection site to hurt afterward?

Yes. It is normal to get mild side effects at the site of injection, including:

• Mild tenderness or soreness

• A small bruise

• Itching or irritation

• A small firm area of skin or lump that goes down in a few days

These side effects should improve over time and rotating the injection spot can help avoid making them worse. If they don’t go away or get worse over time, speak to a healthcare professional. If you notice spreading feelings of warmth, severe swelling, pus or a fever, get medical help as soon as possible.

Look out for signs of an allergic reaction, including swelling of your face, lips, tongue or throat, difficulty breathing or swallowing, or severe dizziness or fainting.

FAQs

Can I inject Mounjaro® into the same spot every week?

It’s best not to. Injecting in the same spot every week increases the chance of side effects, including developing thick or lumpy fatty tissue. It’s best to leave at least 2 to 3cm (a finger’s width) between injection spots.

What if I inject Mounjaro® into the wrong area?

Do not inject yourself again. If you’re not sure whether the medication has been absorbed properly, contact a Hers clinician. Even if you think you may not have gotten the full dose, do not inject again.

Can someone else inject Mounjaro® for me?

Yes. You can have another person perform the injection, as long as they’ve read the instructions and are clear what to do. This is recommended if you want to use the upper arm as an injection site, but you can also have someone else inject your stomach or thigh as well.

Should you pinch the skin when injecting Mounjaro®?

It is not necessary to pinch your skin. The spring-loaded autoinjector used in the Mounjaro® KwikPen® is designed to be used against flat skin and still deliver the injection successfully. Follow the instructions for your medication rather than applying techniques used for other types of injections.

Is it better to inject Mounjaro® in the stomach or thigh?

Neither one is more effective. Either one of them might be better for you depending on your preference. Pick an injection site that is easy to reach and feels comfortable for you.

How deep does the Mounjaro® injection go?

Just under the skin. Mounjaro® isn’t injected as deeply as muscle tissue or veins. The needle is inserted roughly 4mm deep into the skin.

Can you inject Mounjaro® in the bum?

No. The buttocks are not a recommended or approved injection site for Mounjaro®. Injecting Mounjaro® somewhere other than the approved injections sites could mean your medication is not absorbed properly and you don’t receive the full dose.