Once a Month GLP-1: What Is Actually Possible in the UK (October 2026)

01 · The core question

Can you take a GLP-1 once a month?

No licensed GLP-1 weight-loss injection in the UK is taken once a month. Mounjaro (tirzepatide) is a once-weekly injectable medicine, and the weekly schedule is part of how it was designed, tested and licensed.¹ The same weekly rhythm applies to Wegovy. If you want the wider picture of how these medicines are dosed, our guide to GLP-1 once a week explains the schedule in detail.

The confusion is understandable. Mounjaro is sold as a monthly supply, so it feels like a monthly medicine. Each KwikPen contains four weekly doses.¹ You order a pen every four weeks, but you still inject once a week, on the same day each week.

You may also see articles about once-a-month injections in development. Anything in development is not available to prescribe in the UK today.

02 · The one-month question

Can you take a GLP-1 for just a month?

Yes, you can take a GLP-1 for a month and then stop, because treatment is voluntary and you can end it at any time. The more useful question is what a single month will realistically do for you, and the answer is not much.

Everyone starts Mounjaro on 2.5mg once a week. This starting dose is about letting your body adjust, not about weight loss itself.¹ The dose then steps up after at least four weeks. So a single month usually means you spend the whole time on the adjustment dose and never reach the doses that drove the trial results.

That does not mean nothing happens. 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 Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.

03 · Decision guide

Which option fits what you are trying to do?

If your goal is to start, the Mounjaro pen is reviewed by a GPhC-registered prescriber after a free online consultation. Your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). For the wider service, see our weight loss clinic.

Related guide: Once a month weight loss injection.

04 · Why the dose is weekly

Why Mounjaro is a weekly injection

Mounjaro is weekly because the medicine stays active in the body for days, and the schedule was built around that. Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly.¹ It is injected under the skin, on the same day each week, at any time of day, with or without food.¹

You might wonder whether a longer-lasting medicine could simply be injected less often. That is not a decision you or a pharmacy can make. The licensed schedule is weekly, and the leaflet and prescribing information describe weekly use.¹³

There is no best time of day. Mounjaro works the same morning or evening, with or without food, and what matters is the same day each week.¹ Many people choose a weekend morning so early side effects fall on days off.

You can change your weekly injection day if needed, as long as there are at least 3 days between two doses.¹ That flexibility is the only built-in way to shift the timing, and it is not a way to move to a monthly schedule.

05 · What a monthly pen means

What a monthly pen actually is

A monthly pen is a KwikPen that holds enough medicine for weekly injections across a month. Each KwikPen contains four weekly doses.¹

That is why prices are quoted per month. The standard price of a pen at the starting dose is £169.99, and other strengths are priced differently. A first-order discount of £40 applies to new customers with code FIRST40, and every future order is £25 off the standard price (code DOSE25).

The monthly price is a billing rhythm, not a dosing rhythm. Our guide to Mounjaro once a month for maintenance covers holding weight steady.

06 · What one month can do

What to expect from the first month

In the first month, expect adjustment rather than major change. Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month.¹

In the SURMOUNT-1 trial, 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.

A sensible 3-month expectation on a standard titration is mid single digits as a percentage of body weight, with wide individual variation.¹ A single month sits well below that point.

The first days after each injection are when side effects are most likely. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹ Our page on GLP-1 weight loss in one month goes further on pace and what to measure.

07 · Stopping after a month

What happens if you stop after a month

If you stop after a month, you should expect the medicine to leave your system over several weeks and your appetite to return to how it was. Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4–5 weeks to clear the system — there is no way to speed this up, and nothing needs doing while it clears.¹

The larger question is what happens to weight after stopping. Mounjaro manages weight; it does not cure the biology behind it.¹⁴ The evidence comes from a much longer course than a month, but the direction is clear. In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average.¹⁴

A short course followed by a stop is therefore unlikely to leave a lasting change unless habits do the work. Stopping should always be planned with your prescriber, with diet and activity habits ready to carry the load.¹⁴ If you are thinking of a short course, our article on whether you can take a GLP-1 temporarily sets out the planning questions.

08 · Planning the length of treatment

How long should you plan to stay on treatment?

Plan in months rather than weeks, with your prescriber reviewing response along the way. Trials measured results at 72 weeks — think in months, not days, and judge progress by trend, not individual weigh-ins.¹

Titration alone takes time. 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 up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹ A full titration across the ladder is therefore a matter of months. If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices; a new customer's first order is £40 less, and every later order £25 less.

Treatment response is reviewed by your prescriber. 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

Beyond the scales, weight loss on tirzepatide came with average improvements in waist size, blood pressure, cholesterol and blood-sugar measures in trials.² These are trial-average secondary outcomes, not promises, but they explain why prescribers treat this as health management rather than a short-term fix.

09 · Storage and travel

Storage, travel and the monthly 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 at a temperature not above 30°C for up to 30 days after first use — useful for short trips — and must then be thrown away. Do not use a pen that has been above 30°C or has been frozen.¹

This is a storage rule, not a dosing rule. Some people read the 30-day window as a hint that the medicine works monthly. It does not; it only sets how long an opened pen stays usable at room temperature.

You can fly with Mounjaro. Carry pens in hand luggage, ideally in a cool bag with the prescription label or a copy of your prescription.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.

10 · Where to go next

Getting started the licensed way

If a GLP-1 is right for you, the route is a consultation with a prescriber, not a monthly workaround. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

Orders are dispensed by our registered pharmacy (GPhC 9012878), with same-day dispatch when ordered by 3pm and free next-day tracked delivery in temperature-controlled packaging. All six doses are in stock, and ongoing monthly reviews are included.

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

Mounjaro (tirzepatide) 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. Individual results vary. This page is information, not a substitute for medical advice.