Minimum Dose of Mounjaro: What It Is and Why Everyone Starts There (October 2026)

01 · The answer

What is the minimum dose of Mounjaro?

The minimum dose of Mounjaro is 2.5mg, injected under the skin once a week.¹ Everyone starts on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹ The same answer applies to the question 'what is the minimum dose of tirzepatide?', because Mounjaro is the UK brand name for tirzepatide.¹

Mounjaro is a once-weekly prescription medicine made by Eli Lilly. It is licensed in the UK for weight management in adults and for type 2 diabetes, and it comes as a pre-filled multi-dose KwikPen in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹ The 2.5mg pen is the lowest strength and the only one used to begin treatment.

If you want to see how a pen is supplied and priced, our Mounjaro pen page with prices and consultation shows the 2.5mg starter pen. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99).

02 · The ladder

Where the minimum dose sits on the ladder

The minimum dose is the bottom rung of a fixed ladder. After at least four weeks the dose can increase to 5mg, and it can then step up by 2.5mg at a minimum of four-week intervals, up to a maximum of 15mg weekly, depending on how you respond and tolerate it.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

03 · Decision

Is the minimum dose the one that produces weight loss?

Not by design. The 2.5mg dose exists to let your body adjust, and the first weeks are an adjustment phase in which losses are usually modest.¹ Most measurable progress builds from 5mg onward, month by month.¹

That does not mean the starter dose is wasted. It is the part of treatment that makes later doses easier to tolerate. If you are weighing whether to begin, the decision you are really facing is whether you meet the licensed criteria, and how quickly you and your prescriber are comfortable moving up the ladder. Our guides on the minimum weight for Mounjaro and the minimum BMI for Mounjaro cover eligibility, while the weight loss clinic page explains the wider service.

04 · Why start at 2.5mg

Why everyone starts at the lowest dose

Everyone starts at 2.5mg because the starting dose is designed for adjustment, not for weight loss itself.¹ Your body is meeting the medicine for the first time, and a low entry point gives you time to get used to it.

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

The same starting point applies whether you are heavier or lighter, younger or older. There is no licensed way to skip the starter dose. If you have been on Wegovy or Ozempic, there is no licensed direct conversion: your prescriber supervises the switch and starts Mounjaro at a dose they judge appropriate, often the 2.5mg starting dose, sometimes adjusted based on your history.

05 · How long at minimum dose

How long you stay on the minimum dose

You stay on 2.5mg for at least four weeks. The licensed schedule says that after at least 4 weeks the dose increases to 5mg.¹ Each KwikPen contains four weekly doses, so a single 2.5mg pen covers the starting period.¹³

'At least' matters. The four-week interval is a minimum, not a deadline. If side effects are troublesome or your prescriber wants more time at a given step, they can hold you on a dose for longer. Moving up is a clinical decision made with you, not an automatic event on a calendar.

Likewise, once you move to 5mg, later increases come in 2.5mg steps and no sooner than after at least four weeks. Some people never need to go beyond 5mg, and the ladder is a ceiling, not a target. Our guide to upping your Mounjaro dose explains how those decisions are usually made.

Treatment is also reviewed over time. 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 That review is measured on the highest dose you tolerate, not on the starter dose.

06 · Going lower than 2.5mg

Can you take less than the minimum dose?

No. It is not licensed, not supported by the pen's design and not endorsed by any UK regulator.¹

The licensed dose ladder already starts low for tolerability.¹ Altering doses outside the licence means unknown dosing accuracy and no safety data.¹

So the realistic way to be gentle with treatment is to talk to your prescriber about pace. That could mean staying longer on a dose that is working, or stepping down if a dose is too much. It does not mean splitting pens or stretching them.

07 · First weeks on 2.5mg

What to expect during the first weeks

The 2.5mg starting weeks are about adjustment, and experiences differ widely. Some people notice appetite change and early loss in the first week, while others feel little until a higher dose. Both are normal.¹

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 usually settle.¹ If a symptom worries you or does not settle, contact your prescriber, and you can report any suspected side effect through the Yellow Card scheme.¹⁹ If you have severe, persistent stomach pain, or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing, get medical help straight away.

A practical tip: many people choose a weekend morning for their injection so early side effects fall on days off. There is no best time of day, because Mounjaro works the same morning or evening, with or without food. What matters is the same day each week.¹

Weight loss on Mounjaro is gradual by design. Trials measured results at 72 weeks, so think in months, not days, and judge progress by trend, not individual weigh-ins.¹

08 · What the trials show

What the trial results mean for the starter dose

The headline trial figures come from higher doses, not the minimum. In the SURMOUNT-1 trial of 2,539 adults, 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. Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² For someone starting at 100 kg, 20.9% is about 21 kg, but trial averages do not predict your own result.

Notice that the figures begin at 5mg. That fits the 2.5mg dose being there for adjustment rather than weight loss itself. It is a reason to be patient with the starter month, not a reason to rush it.

09 · Injection and storage basics

Injecting the minimum dose: practical points

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 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. Rotate the site with each dose.¹³

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.¹³

You can change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹³

For storage, 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, which is useful for short trips, after which it should be discarded.¹ Keep the pen cap on to protect it from light. Unopened pens keep in the fridge until the expiry date printed on the box. For travel, carry pens in hand luggage, ideally in a cool bag with the prescription label or a copy of your prescription.¹³

10 · Who can start

Who can start on the minimum dose

The minimum dose is only available if you are suitable for treatment. Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber, and it is used alongside a reduced-calorie diet and increased physical activity.¹

On the NHS, 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.⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

For the private route, our free consultation is a short health questionnaire with no charge and no obligation. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. We are a GPhC-registered pharmacy (registration 9012878), and our Mounjaro comes through official LillyDirect supply, directly from Eli Lilly's UK distribution.

Eligibility has several parts. Our guides to the minimum BMI to get Mounjaro and the minimum age for GLP-1 treatment set these out in more detail.

11 · 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