How to Inject Mounjaro: Sites, Steps and Missed Doses (October 2026)

01 · The core answer

How to inject Mounjaro: where, when and how often

Mounjaro is injected under the skin (subcutaneously) once a week, on the same day each week, at any time of day, with or without food.¹ Each KwikPen contains four weekly doses.¹ Follow the pen's instructions each time; the patient information leaflet in the box has the step-by-step pictures.¹³

Your prescriber starts you on 2.5mg weekly and then guides any step up. You can read more in our guide to correctly injecting Mounjaro. If you are still deciding on treatment, the Mounjaro pen costs £169.99 at the 2.5mg starting dose, with all six doses in stock.

02 · Injection sites

Where to inject Mounjaro

You have three licensed injection areas, and which you choose is a matter of comfort and practicality.¹ 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

Want to see it? Our picture of where to inject Mounjaro shows each area, and our page on where not to inject Mounjaro covers areas to avoid. If you wonder whether the site changes results, read does it make a difference where you inject.

03 · Rotation

Rotate the site with each dose

You should rotate the site with each dose.¹ Rotating can mean moving to a different spot within the same area, or alternating between the stomach and the thigh. Keep a simple note, or log each injection in our free GLPTrackr companion app, so you always know where the last one went.

The pen's leaflet explains how to prepare the skin and what to do with the needle afterwards.¹³ If you want to know about the angle, see what angle to inject Mounjaro. If you are comparing sites for effect, see which site is more effective.

Treatment is only part of the story. Alongside the weekly injection you will be following a reduced-calorie diet and increasing physical activity, and our weight loss clinic pages explain the wider programme.

04 · Using the KwikPen dial

Using the KwikPen dial and the “clicks” question

People often ask how many clicks make up 2.5mg, and the answer is that you never count them. You set the dose by turning the dose knob until the dose indicator shows the correct dose in the window.

The same rule applies at every strength, from 2.5mg to 15mg. Check the window each time, because you may move to a new strength as your prescriber guides you. Check the strength on the pen label before you dial.

The leaflet that comes in the box has the step-by-step instructions for preparing and using the pen.¹³ Our complete PDF guide to injecting Mounjaro adds pictures you can keep to hand. Many other weekly pens work in a similar way, and our overview of how to inject GLP-1 medicines covers the shared principles.

05 · Day and time

Choosing your injection day and time

There is no “best” time of day, because Mounjaro works the same morning or evening, with or without food.¹ 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, and then stick to it.¹

So if you are wondering whether to inject in the morning or at night, choose whichever you will actually remember. A phone reminder or a note in your calendar helps in the early weeks.

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 Tell your prescriber at your next review if you change day, so your records stay accurate.

06 · Missed doses

What to do if you miss a dose

The rule is simple and depends on how late you are. 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.¹

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 Never double up to catch up.

07 · Storage and travel

Storing your pen and travelling with it

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.¹ 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 (hold luggage can fall below freezing), ideally in a cool bag with the prescription label or a copy of your prescription. In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements; for hot climates use an insulated pouch. Check destination rules for travelling with prescription injectables before you fly.¹³

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 — figures circulating online often come from other countries' labels.¹³

08 · After the injection

What to expect after you inject

The 2.5mg starting weeks are about adjustment, and experiences differ widely. Some people notice appetite change and early loss in week one, others feel little until a higher dose — both are normal.¹ Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹

Weight loss on Mounjaro is gradual by design. The early weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month. Trials measured results at 72 weeks, so think in months, not days, and judge progress by trend rather than individual weigh-ins.²

Early loss includes water weight, so the trend over weeks matters more than any single weigh-in. Your prescriber reviews your response. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, they will discuss whether continuing or stopping is right for you.²

For symptoms you are unsure about, speak to your prescriber, and you can report suspected side effects through the Yellow Card scheme.¹⁹

09 · Getting your pen

Getting a Mounjaro pen from us

We are a GPhC-registered UK online pharmacy (GPhC 9012878) and supply genuine KwikPens through official LillyDirect supply. Ordering takes a few steps: a free online consultation, a review by a GPhC-registered prescriber, then dispensing and free next-day tracked delivery in discreet, temperature-controlled packaging. Same-day dispatch applies when you order by 3pm.

Needles, a sharps bin and injection guidance are included with every order, so you have what you need on the day the pen arrives. See the Mounjaro pen prices and consultation page, or compare options in where best to inject Mounjaro with a private UK provider and where to inject Mounjaro: how does it compare.

10 · Serious side effects

Serious side effects: when to get help straight away

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 take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹