How to Inject GLP-1 Medicines: Sites, Timing and Technique (October 2026)

01 · The core answer

Where to inject GLP-1 medicines

You inject into the fat just beneath the skin, not into muscle or a vein. Licensed injection sites are the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection.¹

If you are on your own, the stomach or thigh is the realistic choice.

If you want a closer look at each area, our guides cover injecting into the thigh, a picture of the injection areas, and whether the site changes how it works.

02 · Your next decision

Rotating sites and choosing your day

Rotate the site with each dose.¹ A simple habit is to move between the stomach and each thigh in turn, or to shift a little to a fresh patch of skin within the same area. Rotation keeps one patch of skin from being used repeatedly.

For timing, there is no "best" time of day. Mounjaro works the same morning or evening, with or without food. What matters is the same day each week. Pick a day and time you will remember; many people choose a weekend morning so early side effects fall on days off.¹

Our weight loss clinic explains how a consultation works.

03 · Step-by-step technique

How to inject: the routine

The full, illustrated steps for your pen are in the patient information leaflet that comes in the box, and you should follow those over any general guide.¹³ Needles, a sharps bin and injection guidance are included with every order from us.

In outline, the routine looks like this:

• Take the pen from the fridge, and check it is the medicine and dose you expect.
• Choose a site from the licensed list and use a different spot from last time.
• Dial the dose using the pen's knob until the number in the window is correct.
• Inject under the skin following the pen's own instructions, and keep the pen in place for as long as those instructions say.
• Put the used needle in a sharps bin and replace the cap on the pen.

Every pen differs in how the needle is attached and how the button works, so this is an outline, not a substitute for the leaflet.

04 · Reading the dose

How much do you inject, and how do you read the dial?

The amount you inject is your prescribed dose, set by your prescriber, not something you work out yourself. Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹ After at least 4 weeks the dose increases to 5mg, and can then step up by 2.5mg at a minimum of 4-week intervals, depending on how you respond and tolerate it. Higher is not automatically better.

The Mounjaro KwikPen is set by turning the dose knob until the dose indicator shows the correct dose in the window. Each KwikPen contains four weekly doses.

05 · Missed or moved doses

What if you miss a dose or want to change day?

If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day. If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day — never take two doses within 3 days of each other.¹

You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹ This is useful if your routine changes, for example a new shift pattern. Move the day once, then keep to the new one.

These rules are for Mounjaro. Other GLP-1 medicines, including daily liraglutide, have different schedules, so check the product information for the medicine you use.

06 · Storage and travel

Storing and travelling with your pen

Keep Mounjaro pens in a fridge at 2–8°C and never freeze them. 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.¹

You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription. For hot climates use an insulated pouch, and check destination rules for travelling with prescription injectables before you fly.¹

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit.

07 · Common mistakes

Can you inject GLP-1 wrong?

Yes, but the common errors are easy to avoid.

Aim for the fatty layer under the skin, as the licence describes, and keep the pen cap on between uses and the pen stored as directed.¹ If you think a dose did not deliver properly, do not inject a second one to make up for it. Contact your prescriber or the pharmacy for advice first.

Serious side effects are uncommon but need urgent attention. 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 skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you notice any other new symptom after injecting, tell your prescriber and consider reporting it through the Yellow Card scheme.¹⁹

08 · Does the site matter?

Does it matter where you inject?

The licensed sites are the ones the product information supports, so stick to them.¹ Within those areas, the choice is mostly comfort and convenience. Many people pick the stomach or thigh because they can see and reach them easily.

If you want more depth, see where is best to inject Mounjaro and whether the site makes a difference. For other medicines, a general site overview is useful, but always check the leaflet for the pen you hold.

09 · Supply and support

Support with injecting at home

If you are new to self-injecting, you do not have to work it out alone. We are a GPhC-registered UK online pharmacy (registration GPhC 9012878), and Mounjaro comes through official LillyDirect supply as genuine KwikPens. Orders are reviewed by a GPhC-registered prescriber after a free online consultation.

Delivery is free, next-day, tracked and in temperature-controlled packaging, with same-day dispatch when ordered by 3pm. Ongoing monthly reviews are included, so you can raise injection worries with the prescribing team. Our Wegovy pen is also available if you and your prescriber decide it suits you better; each pen has its own instructions.