How to Choose a Weight Loss Drug in the UK (October 2026)

01 · The core answer

How to choose a weight loss drug: the short version

Choose by working through a fixed order of questions: am I eligible, which medicines suit my health, how will I take it, what will it cost over time, and who will review me? Doing it in that order stops you falling for a headline result or a low first-month price.

Licensed weight loss medicines are prescription-only. That means the real decision is shared between you and a prescriber. Your job is to arrive with clear answers about your health, your medicines, your past attempts at weight loss and your practical limits. Their job is to confirm which options are safe for you.

02 · Your decision

The questions that decide which drug fits you

Five questions narrow the field far more than any ranking list. Write your answers down before you speak to a prescriber, because they shape every recommendation.

• Am I eligible? Licensed criteria rest on your BMI (kg/m²) and on weight-related conditions.
• What else do I have and take? Type 2 diabetes, heart conditions, past pancreatitis, other medicines and contraception can all change what is suitable.
• What routine will I keep? A once-weekly injection suits people who dislike daily tasks. A daily injection suits some people who want a regular anchor. Tablets suit people who dislike needles.
• How do I handle side effects? Nausea and appetite change are common early on. Your tolerance and how slowly you want to step up matter.
• What can I sustain financially? Weight management medicines are used over months, so total cost over the course matters more than any single month.

03 · Compare

Weight loss medicine options compared

This table compares how the main prescription options are used. Trial results from different studies cannot be set side by side, so the table does not rank the options.

Tablets and injectables are different products with different trials. Never read one product's trial headline against another's as though they were tested together.

04 · What next

What to do once you have a shortlist

Take your shortlist to a prescriber rather than deciding alone. Our weight loss clinic offers a free online consultation reviewed by a GPhC-registered prescriber, 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.

05 · Eligibility and NHS access

Eligibility, the NHS and private treatment

Eligibility is the first filter, and it differs between the NHS and private prescribing. Mounjaro is available on the NHS, but access is being phased in over several years.⁴

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.

NHS access to Wegovy runs through specialist weight-management services; ask your GP. Whichever route you take, the question you are answering is the same: is this medicine appropriate for my body and my health history? If the NHS route is open to you, it is worth exploring first.

Private treatment is not a shortcut around safety. A reputable provider should be on the GPhC register, which you can check yourself.¹² We are registered under GPhC 9012878.

06 · How the drugs differ

How the main drugs differ in practice

The practical differences are the mechanism, the frequency and the dose ladder. Tirzepatide is the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1.¹ Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.

In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet. This dual action is what distinguishes Mounjaro from single-action medicines such as semaglutide (Wegovy/Ozempic).¹ Distinguishing is not the same as ranking: both are licensed, effective treatments, and the right one depends on you.

Wegovy follows a fixed ladder of 0.25mg, 0.5mg, 1mg, 1.7mg and 2.4mg, stepping up after 4 weeks on each of 0.25mg, 0.5mg, 1mg and 1.7mg, with the 2.4mg maintenance dose starting from week 17.¹⁸ Liraglutide is a daily injection at 6mg/ml, unlike once-weekly Mounjaro and Wegovy.

Oral options are newer. Wegovy tablets and Foundayo are taken as tablets rather than injections, and each has its own product information.²⁰²¹ If needles are your main barrier, ask a prescriber whether a tablet is suitable for you rather than assuming either way.

For wider context, you may also want to see whether a medicine you have heard about is really for weight loss. For example, whether Jardiance counts as a weight loss drug is a common question, and naltrexone-based combinations come up often too. A prescriber can explain whether either is relevant to you.

07 · Dosing and pace

Dosing, titration and realistic pace

Dosing should be gradual, and higher is not automatically better. Everyone starts Mounjaro on 2.5mg once a week.¹ This starting dose is about letting your body adjust, not about weight loss itself.

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 (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it. Many people settle at a maintenance dose of 5mg, 10mg or 15mg, and your prescriber will guide the right pace.¹

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. Trials measured results at 72 weeks, so think in months, not days, and judge progress by trend, not individual weigh-ins.²

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.⁴

08 · Side effects and safety

Side effects and safety: what to weigh

Side effects are a core factor in choosing, because you are more likely to keep taking a medicine you tolerate. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹³

The first weeks differ widely between people. Some notice appetite change and early loss in week one, while others feel little until a higher dose. Both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in.¹³

Tell your prescriber about any new or lasting symptom. Tell your prescriber about any new or worrying symptom, including changes in mood. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹ Regulators have looked at whether GLP-1 medicines are linked to low mood or suicidal thoughts, and the EMA's safety committee concluded in 2024 that the evidence does not support a causal link.¹⁷ Tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment. If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

Disclose all your medicines, including insulin or sulfonylureas. Doses of those may need adjusting because of the risk of low blood sugar, which is a conversation for your prescriber rather than a reason to avoid treatment automatically.

09 · Cost over the course

Cost: think about the whole course, not one pen

Cost should be judged over the whole course, because dose, duration and reorders all change the total. At our pharmacy, the standard price of the 2.5mg pen is £169.99 per month, and your first 2.5mg pen costs £129.99 with code FIRST40. Every later order is £25 off the standard price.

Titration costs more than a single pen because you pass through several strengths. If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices, before discounts. A first year costs £2,711.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,599.88 if you step up through every dose to 15mg. A new customer's first order is £40 less and every later order £25 less.

Across the UK pharmacies we track, the cheapest Mounjaro pen at any dose is £143.96 and the dearest is £339.00 (checked 11 October 2026). A low price matters, but so do genuine supply, prescriber review and follow-up.

Be wary of very cheap offers. Anyone offering to supply a prescription medicine without a consultation or prescription is a warning sign, and counterfeit medicines are the risk the MHRA alerts people to.⁷

10 · Warning signs and older drugs

Red flags, old drugs and supplements

Treat any product that promises dramatic weight-loss claims with caution. Licensed medicines are prescription-only for a reason: they need assessment, dosing guidance and follow-up. Supplements marketed as natural alternatives are low-cost supplements with no clinical oversight, and their dosing is not standardised.

You may come across names from earlier decades of weight loss treatment. Pages such as fen-fen, Meridia and Belviq look at those names. They are useful background, but they are not what a UK prescriber would be comparing today.

Check that any pharmacy appears on the GPhC register and that a prescriber reviews you before supply. If a seller will not ask about your health, walk away. Genuine supply comes from regulated routes; we supply Mounjaro through official LillyDirect supply, sourced from Eli Lilly's UK distribution.⁷

11 · Staying on track

Maintaining weight and living with the choice

Choosing a drug also means choosing how you will live with it. Mounjaro is used alongside a reduced-calorie diet and increased physical activity, and it is not a substitute for them.¹ Plan the habits you will build while appetite is lower: regular protein, enough fluids, movement you enjoy.

Choose a routine you can repeat. Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food. There is no best time of day; what matters is the same day each week.¹

Think too about what happens afterwards. 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. Stopping should always be planned with your prescriber, because in SURMOUNT-4 people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year.¹⁴

Our aftercare includes ongoing monthly reviews, dose titration and follow-up assessments by the prescribing team, plus side-effect support. Repeat orders re-check suitability, and nothing ships automatically. The free GLPTrackr app can help you log your progress.

12 · 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