What Part of the Thigh Do You Inject Mounjaro? (October 2026)

01 · The core answer

Which part of the thigh should you inject Mounjaro into?

Aim for the front of the thigh, on the fleshy upper part of the leg between the hip and the knee. This matches the UK product wording, which names the front of the thigh as a licensed site.¹ The patient information leaflet shows the same sites with diagrams, and it is worth having it open the first time you inject.¹³

In practice, sit down with your leg relaxed, so the skin and the layer of fat beneath it are soft. Choose a patch of healthy skin. Avoid areas that are bruised, scarred, sore, irritated or have a recent injection mark. Keep clear of the area right above the knee and well away from the hip crease, where there is little padding and more movement.

Mounjaro is injected under the skin, once a week, on the same day each week, at any time of day, with or without food.¹ That is the whole target: the layer just beneath the skin, not deeper muscle. Follow the pen's own instructions for how to place and use it rather than relying on a rule of thumb from a video.

02 · Common question

Can you inject Mounjaro in the inner thigh?

The inner thigh is not a licensed Mounjaro injection site. The licensed list is the stomach area, the front of the thigh, and the back of the upper arm if someone else gives the injection.

So if you are asking whether you can use the inside of the leg, the safe answer is to stay on the front of the thigh. We have a separate page on the inner thigh question in more detail. If you have already used the inner thigh once, do not panic. Use a licensed site next time, and mention it to your prescriber if you notice anything unusual.

03 · Choosing a site

Mounjaro in the stomach or the thigh: which should you choose?

Choose whichever licensed site you can reach easily, see clearly and keep rotating. The product information lists the stomach area and the front of the thigh together and does not rank them. If you want the full comparison, read our guide on thigh versus stomach, or the page asking which is better for you.

When people ask whether one site is more effective, the honest position is that the labelled sites are all licensed routes into the same under-the-skin layer. Your weight-loss result depends on the dose, your diet and activity, your response and how consistently you take it. Individual results vary. Our page on whether Mounjaro is more effective in stomach or thigh covers this in full.

04 · Thigh injection step by step

How to inject Mounjaro into your thigh

Use the instructions in your pen's leaflet as your master guide; this is a practical overview, not a replacement.¹³ Wash your hands, check the pen and the medicine, and choose a clean, healthy patch on the front of the thigh. Sit comfortably so the muscle under the skin is relaxed.

Follow the pen's instructions for removing the cap, placing the pen against the skin and delivering the dose. Do not guess or improvise. When the injection is finished, dispose of the used needle safely in the sharps bin supplied with your order.

Each KwikPen contains four weekly doses.¹ Keep a note of which site you used each week. Many people write the side and area on a calendar or use a tracking app such as our free GLPTrackr companion app, so rotation is never left to memory.

For a longer walkthrough aimed at this exact topic, see our guide on how to inject a GLP-1 pen in the thigh, and our page on using the thigh for Mounjaro.

05 · Rotating injection sites

Rotating your injection site

Rotate the site with each dose; this is part of the licensed instruction.¹ You can rotate between the left and right thigh, or move between the thigh and the stomach area. What matters is that you do not keep injecting into exactly the same spot.

A simple routine works well: pick a side, pick a patch, and next week move to a fresh patch or the other leg. Within the same area, shift sideways a finger-width or more from the previous mark so you are always on unmarked skin. Stay within the front of the thigh, away from the inner thigh and the area close to the knee.

Why bother? Repeated injections in one place can leave the skin tender or lumpy, and that makes the next injection less comfortable. The product information also recommends rotating sites for this practical reason. If a patch looks bruised, feels hard or is sore to touch, simply choose another spot until it has settled.

Some people like a pattern: thigh one week, stomach the next. Others prefer to stay on the thighs for months because it feels easier. Both are fine as long as you rotate within the licensed areas and never inject into damaged skin.

06 · Stomach injection comparison

The stomach option: where on the abdomen

The stomach area is the other widely used site, and the label gives one precise rule: keep away from the belly button. Beyond that, choose soft, healthy skin and rotate around the abdomen.

The stomach suits people who find the thigh awkward to reach or who find a seated abdominal injection easier to see. The thigh suits people who prefer to look at what they are doing from a seated position or who find the abdomen tender, especially if they feel bloated on higher doses. Our page on where to inject Mounjaro in the abdomen goes through the area by area detail.

The back of the upper arm is also licensed, but only if someone else gives the injection, because it is hard to do safely on yourself. If you have a partner or carer who helps, it can be a useful third option for rotation.

07 · Injection mistakes

What if you inject in the wrong place or not deep enough?

If you think an injection went wrong, stay calm, do not repeat the dose, and read the leaflet. Mounjaro is designed as a once-weekly under-the-skin injection, and the pen's instructions cover correct use. Contact your prescriber or pharmacist and describe what happened.

Never take two doses within 3 days of each other.¹

If you notice a new or worrying symptom after an injection, tell your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹

Seek immediate medical help for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of the skin or eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.¹

08 · Site reactions and comfort

Injection-site reactions and how to reduce stinging

Mild redness, itching, a small bruise or a tender lump at the injection site is common and normally settles within a few days.¹ Rotating sites each week and letting the pen warm briefly out of the fridge reduces stinging. Contact your clinical team if a reaction is spreading, hot, very painful, or lasts more than a week.

In the weight-management trials, injection-site reactions were reported by 8.0% of people taking tirzepatide, compared with 1.8% on placebo.¹

Ways to make the thigh injection more comfortable: relax the leg, use a fresh patch each week, avoid skin that is still tender from the last dose, and avoid injecting straight after a hot bath, when skin may be more sensitive. If one patch is consistently sore, choose another licensed site.

Which part of the thigh hurts least? It varies from person to person. The licensed area is what matters, and your own experience is the best guide.

09 · Storage before injecting

Storing the pen before you inject

Keep Mounjaro pens in a fridge at 2–8°C and never freeze them.¹ Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days, useful for short trips, after which it should be discarded. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.

For unopened pens, store them in the fridge until first use; they keep until the printed expiry date. If you have a question about an unopened pen that has been out of the fridge, check the patient information leaflet and ask the pharmacy rather than guessing.¹³

Letting the pen warm briefly out of the fridge before injecting can reduce stinging.

10 · Starting and getting support

Getting started with Mounjaro in the UK

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you choose private treatment, the process is simple: a free online consultation, a review by a GPhC-registered prescriber, dispensing by our registered pharmacy and free next-day tracked delivery in temperature-controlled packaging, with same-day dispatch when ordered by 3pm.

Mounjaro is a prescription-only medicine used alongside a reduced-calorie diet and increased physical activity. Individual results vary. Our weight loss clinic page explains the wider programme, including monthly reviews and side-effect support from the prescribing team.