What Dose of Mounjaro Do You Start On? (October 2026)

01 · The answer

The Mounjaro starting dose is 2.5mg once a week

Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹¹¹ That is true whether you are just above the BMI threshold or well above it.

Mounjaro is the brand name for tirzepatide, and the 2.5mg pen is the licensed starting strength. Mounjaro comes as a pre-filled multi-dose KwikPen in strengths of 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

Your prescriber decides the pace after that. Our weight loss clinic page explains how treatment is supervised.

02 · Step by step

The dose ladder after you begin

After the starting dose, the licence allows the dose to rise in set steps. This table shows the licensed route, with the minimum time before each step.¹

Many people settle at a maintenance dose of 5mg, 10mg or 15mg. Higher is not automatically better, and your prescriber will guide the right pace.¹ Our guide to the right Mounjaro dose to take covers how that decision is made.

03 · Next step

What to do next

If you are ready to begin, a free online consultation is reviewed by a GPhC-registered prescriber. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. A new customer can use code FIRST40 on a first order, and an automatic £25 reorder discount applies to every future order (code DOSE25). You can see current prices and start the consultation on the Mounjaro pen page.

04 · Why 2.5mg first

Why everyone starts on 2.5mg

The licensed ladder starts low for tolerability. Tirzepatide activates two natural gut-hormone receptors at once, GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹ Starting low gives your body time to get used to those effects.

That is why the 2.5mg weeks are not where most of the weight loss happens. In the SURMOUNT-1 trial, the results quoted for tirzepatide were at 5mg, 10mg and 15mg, not at the starting dose. People taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² These are trial averages, and individual results vary. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.

05 · Starting higher?

Can you start on a higher dose?

No. The licensed starting dose is 2.5mg for everyone, so a higher first strength is not part of the licence.¹ Wanting faster results is understandable, but skipping the adjustment phase is not an option your prescriber can offer within the licence. We explain this in more detail in our page on starting on a higher dose.

If you have been treated by another provider and are moving to us, tell the prescriber during your consultation which dose you were on and for how long. They will decide what is suitable for you. Do not choose a strength yourself on the basis of what a friend or a forum post says.

06 · The first weeks

What the first weeks on 2.5mg feel like

Experiences differ widely. Some people notice appetite change and early loss in the first week, others feel little until a higher dose, and both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.¹

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects, and they usually settle.¹³ Many people choose a weekend morning for their injection so early side effects fall on days off. 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.

For a fuller picture of when to expect results, see at what dosage Mounjaro starts working.

07 · Moving up the ladder

How and when you move to the next dose

The earliest you can step up is after at least four weeks. That is a minimum, not a target. Your prescriber reviews how you are tolerating treatment and how you are responding, then decides whether to move up or hold.¹ Holding a dose for longer is a normal clinical decision, not a failure.

Each pen holds four weekly doses. A new strength means a new pen, so the step-up happens when you start the next one. Our guide to the mg you start on shows how the strengths line up.

08 · Injecting basics

Injecting your first dose

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day. Licensed 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. Rotate the site with each dose.¹ Follow the pen's instructions for the injection itself. Needles, a sharps bin and injection guidance come with every order.

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, and never take two doses within 3 days of each other.¹

Keep pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Do not use a pen that has been above 30°C or has been frozen.¹³

09 · 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

10 · Review and NHS

Review points and NHS access

Progress is reviewed by your prescriber over months, not days. Weight loss on Mounjaro is gradual by design, and most measurable progress builds from 5mg onward. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you.¹ Our ongoing monthly clinical reviews cover this follow-up.

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).⁴⁶ Pregnancy: Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly. The starting dose is the same on the NHS and privately. Still unsure whether treatment is right for you? Read whether you should start a GLP-1.

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. This page is information, not a substitute for medical advice.