How Weight Loss Injection Programs Work in the UK

Step 1: Clinical assessment before the first injection

Everything starts with the consultation. Before a single dose is prescribed, a clinician needs to understand your weight history, current health conditions, any medicines you take, and whether this class of treatment is appropriate for you. For Mounjaro, the licensed starting point is adults with a BMI of 30 or above, or 27 or above alongside a weight-related condition such as high blood pressure, high cholesterol, or obstructive sleep apnoea. Wegovy follows similar thresholds. Lower BMI cut-offs can apply for certain ethnic backgrounds under UK guidance.

At nume, this assessment is reviewed personally by a GPhC-registered Independent Prescriber (a real clinician, not software) on the same day you submit it. Identity is verified with photo ID, and current weight is confirmed on a live video call. If you are transferring from another provider, evidence of your current dose is checked before any continuation is approved. That process exists because the program only works safely when the dose matches where you actually are.

The NICE appraisal of tirzepatide (TA1026) and the equivalent guidance for semaglutide both make clear that these medicines are intended to work alongside a reduced-calorie diet and increased physical activity, the injection program supports lifestyle change; it does not replace it.

Step 2: Starting low and building gradually

Neither Mounjaro nor Wegovy begins at its full therapeutic dose. Mounjaro starts at 2.5 mg, a level designed to let your digestive system adjust before the dose rises. Wegovy begins at 0.25 mg for the same reason. From there, both programs increase in steps, typically every four weeks, guided by how well you are tolerating the current dose and what your prescriber sees when they review your progress.

A question our prescribers hear most weeks is whether it is safe to speed up the titration to reach a higher dose faster. The honest answer is that the schedule exists specifically to reduce nausea, vomiting, and the other gastrointestinal effects that are most common in the early weeks of weight loss programs with injections. Moving too quickly tends to mean more side effects, not better results. Your prescriber decides the timing; the patient information leaflet sets the framework.

If you want a fuller picture of how the two medicines compare at each stage, our overview of weight loss injections available in the UK covers the differences in mechanism and schedule side by side.

Step 3: Injection technique and weekly routine

Both medicines are given as a small subcutaneous injection (into the layer of fat just beneath the skin) once a week, on the same day each week. The three approved sites are the abdomen, the front of the thigh, and the upper arm. Rotating between sites week to week reduces the chance of irritation or lumps building up at any one spot.

The pen itself is pre-filled and pre-set; there is no need to draw up a dose or measure anything. The needle is short and fine. Most people find the injection far less daunting in practice than they expected, a feeling the NHS patient information for tirzepatide, available at nhs.uk/medicines/tirzepatide, describes alongside practical guidance on what to do if you miss a dose.

Used needles must go into a sharps container, not a household bin. If you need one, a one-litre sharps container is available from our pharmacy. Both medicines require refrigeration between 2–8°C; for the exact room-temperature window if you are travelling or your pen is temporarily unrefrigerated, always check the patient information leaflet that comes with your specific pen.

Step 4: Ongoing clinical review at each repeat

A weight loss injection program does not end after the first pen. Every repeat order through nume involves a fresh clinical review, not a rubber stamp, but a genuine check that the dose still suits you, that there are no new concerns, and that the program is delivering meaningful progress. If a dose increase is due, the prescriber looks at the evidence before approving it. If something in your health picture has changed, that changes the clinical conversation too.

For anyone considering what a private program actually costs relative to what it includes, our guide to weight loss injection pricing in the UK sets out what transparent pricing should cover and what some headline figures leave out. It is also worth understanding the risks and side effects associated with these injections before you begin, GI symptoms are common early on, and there are rarer but serious signs, including severe stomach pain that might indicate pancreatitis, that always warrant prompt medical attention.

When you feel ready to talk through whether an injection program suits your situation, you can read more about choosing the best weight loss injection program for your needs, or if you prefer to manage everything remotely, our guidance on finding the best online weight loss injection program explains what to look for in a provider. When you are ready to take the next step, speak to our prescribers through a free consultation, no commitment, just a thorough clinical assessment from a UK-registered prescriber.