Weight-loss injections, without the hype.
A clinician's honest guide to Mounjaro and Wegovy — what they do, what they don't, and what really happens when you start, scale up, or come off them.
If you've arrived here, you've probably read a dozen breathless headlines about "skinny jabs" and walked away more confused than informed. This guide is different. I'm going to walk you through exactly what I tell my patients in clinic — the genuine benefits, the real trade-offs, and what the treatment actually feels like month by month.
What are weight-loss injections?
The two medications prescribed in the UK in 2026 are Mounjaro (tirzepatide) and Wegovy (semaglutide). Both are once-weekly injections given under the skin with a small pre-filled pen. They belong to a class of drugs called incretin mimetics — they imitate gut hormones your own body releases after a meal.
The effect is threefold: you feel fuller faster, you stay fuller for longer, and the background "food noise" many people describe — the constant pull toward the fridge, the snacking, the planning of the next meal — quietens down substantially. Mounjaro acts on two hormonal pathways (GLP-1 and GIP); Wegovy acts on one (GLP-1). That's the key mechanistic difference, and it shows up in the trial data below.
A once-weekly injection that targets two appetite-regulating hormones. Clinical trials have produced the most impressive weight-loss figures seen in this drug class to date. Typically tolerated well when titrated slowly.
The original weight-loss GLP-1. Strong cardiovascular outcomes data from the SELECT trial — particularly relevant if you have existing heart disease. A higher 7.2 mg dose became available in the UK in January 2026 for patients plateauing at 2.4 mg.
In head-to-head data (SURMOUNT-5), Mounjaro produced greater average weight loss than Wegovy at standard doses — roughly 20% versus 14%. But averages obscure the individual. I've had patients lose more than 20% on Wegovy and patients plateau at 8% on Mounjaro. Personal factors matter: cardiovascular history, tolerance of side effects, cost over a year, and whether you have type 2 diabetes.
In short: Mounjaro tends to produce greater weight loss on paper; Wegovy has the strongest cardiovascular evidence and is usually more affordable at maintenance dose. Neither is objectively "better" — the right answer depends on your clinical picture.
Am I eligible? A quick self-check
Before we go further, a practical question: does treatment even make sense for your situation? UK licensing requires a BMI of 30 or above, or 27 or above with a weight-related condition (such as high blood pressure, prediabetes, obstructive sleep apnoea, joint problems, or fatty liver). The calculator below gives you an immediate indication.
Eligibility Calculator
Enter your details for a quick guide. This is not a substitute for a clinical consultation — it simply tells you whether licensing criteria are likely to apply to you.
The genuine pros — what these drugs do well
I want to be direct: these are the most effective weight-loss medications the pharmaceutical industry has ever produced. Dismissing them as a fad or a shortcut misunderstands what they are. But the upsides are specific, not universal.
✓ What works
- Meaningful weight loss. Typical results of 10–20% of starting body weight over 12–18 months — an order of magnitude beyond what diet and exercise alone achieve on average.
- Reduced "food noise." Many patients describe this as the single most striking change: intrusive food thoughts simply fade.
- Improved metabolic markers. HbA1c, blood pressure, lipid profile, liver enzymes and sleep apnoea severity all tend to improve alongside weight loss.
- Cardiovascular protection. For semaglutide specifically, a 20% reduction in major cardiac events (SELECT trial) — independent of the weight loss itself.
- Once-weekly dosing. A single injection, no calorie-counting apps, no daily tablets.
⚠ The trade-offs
- Gastrointestinal side effects. Nausea, reflux, constipation or diarrhoea are common — particularly at dose increases. For most they settle within days; for a minority they don't.
- Muscle loss. A real concern, especially in older patients or those who don't strength-train. Up to a quarter of weight lost can be lean mass without deliberate countermeasures.
- Cost. Private prescription cost varies but typically £150–£300 per month depending on dose and provider.
- Weight regain on stopping. Without a structured maintenance plan, the majority of lost weight returns within 12 months of discontinuation. This is a chronic-disease medication, not a cure.
- Less-common but serious risks. Pancreatitis, gallbladder disease, reduced contraceptive pill absorption, and thyroid concerns (class warning — no confirmed human link).
- Not for everyone. Contraindicated in pregnancy, breastfeeding, history of medullary thyroid cancer, or active severe GI disease.
The injection is a tool, not a transformation. The patients who succeed long-term are the ones who use the months of reduced appetite to rebuild their relationship with food, movement and sleep — so that if they ever stop, the new habits hold.
Your journey, week by week
Patients often arrive anxious about the injection itself and unsure what the first few months will actually feel like. Click through the phases below — this is what typically happens.
The first injection
You'll start on the lowest available dose — 2.5 mg for Mounjaro or 0.25 mg for Wegovy. These are deliberately sub-therapeutic: the purpose is to let your body adapt, not to drive weight loss. The injection goes into the fatty tissue of the abdomen, thigh or upper arm. It takes about five seconds and most patients describe it as a mild pinch.
What to expect: a softer appetite from about week two. Fullness arriving sooner, portion sizes shrinking naturally. Some mild nausea — particularly after larger or fattier meals — often settling within days. A few patients experience reflux or constipation. Hydration and smaller, protein-forward meals make a significant difference. You likely won't see dramatic weight loss yet, and that's expected.
Finding your therapeutic dose
Doses increase every four weeks, provided side effects are manageable. Mounjaro goes up in 2.5 mg increments; Wegovy doubles through four steps to 2.4 mg. This is where most of the weight loss happens — 1 to 2 kg per month is a healthy, sustainable rate.
Important: there is no rule that says you must reach the maximum dose. I commonly hold patients at 5 mg or 7.5 mg of Mounjaro if weight loss is tracking well and side effects are mild. Higher doses mean higher cost and a greater side-effect burden — they should be earned, not assumed. If a dose increase triggers significant nausea, we hold or step back. Sustainable progress matters more than hitting a number on a protocol.
Maintenance dose
At some point — often between month 6 and month 12 — weight loss slows and plateaus. This is normal and expected. The body recalibrates at a new setpoint, and further weight loss usually requires either a dose increase, more aggressive lifestyle change, or accepting the current result.
What I focus on here: protecting muscle mass (resistance training at least twice a week is non-negotiable), ensuring adequate protein intake (around 1.2–1.6 g per kg of ideal body weight), vitamin and mineral status, and the psychological work of rebuilding a healthy relationship with food while appetite is still suppressed. The NICE rule of thumb is that if a patient hasn't lost at least 5% of their starting weight after six months on the highest tolerated dose, continuing treatment isn't justified.
Lowering and coming off
This is the least-discussed part of the treatment and arguably the most important. When people stop abruptly, appetite returns — often sharply, sometimes disinhibited — and weight regain follows. The STEP 4 trial showed an average two-thirds of lost weight regained within a year of stopping semaglutide. This is not a failure of the drug; it reflects the biological reality that obesity is a chronic condition and the medication was managing it.
My approach to coming off: staged dose reduction over 3–6 months, not a sudden stop. Each dose step down lasts at least a month. We tighten lifestyle structure simultaneously — formal strength training, protein targets, a clear eating rhythm, sleep hygiene, and weekly weigh-ins. For many patients the best answer is not to come off at all, but to step down to the lowest effective maintenance dose indefinitely. The decision is individual and clinical — not a moral one.
What good treatment looks like
A quality weight-loss service is not a prescription pad. The medication is the easy part. What decides your outcome — whether you lose 5% and plateau or lose 18% and keep it off — is the clinical scaffolding around the injection.
At Hinchley Medical, that scaffolding includes a full metabolic workup before starting (bloods, body composition, cardiovascular risk), individualised titration rather than a one-size-fits-all ladder, regular reviews to catch side effects early, active protection of muscle mass, and — the part most services skip — a genuine plan for maintenance and deprescribing. You are buying a partnership, not a pen.
Frequently asked questions
Averages from trial data: around 20% of body weight on Mounjaro and 15% on Wegovy over 12–18 months. But individual results vary enormously. About 10% of patients are "super-responders" who lose 25% or more; another 10% lose less than 5% even at maximum tolerated dose. Your response in the first three months is usually a reliable guide to your long-term trajectory.
The needle is very fine — shorter and thinner than an insulin needle. Most patients describe it as a brief sting or pinch. The injection takes about 5 seconds. Rotating injection sites (abdomen, thigh, upper arm) prevents local irritation.
If you're within 4 days of the missed dose, take it as soon as possible and carry on as normal. If more than 4 days have passed, skip the missed dose entirely and take the next one on your usual day. Never double-dose to catch up — this causes severe GI side effects.
Some muscle loss is inevitable with any rapid weight loss — this is not unique to GLP-1 drugs. Evidence suggests 20–40% of weight lost on these medications is lean tissue unless you deliberately protect it. The two things that work: adequate protein intake (around 1.2–1.6 g per kg of ideal body weight daily) and resistance training at least twice a week. Without these, you'll end up lighter but weaker — which is not the goal.
Yes, but many patients find their tolerance drops markedly — a glass or two can feel like four. There's also emerging evidence that GLP-1 drugs reduce alcohol cravings, which some patients welcome. Avoid heavy drinking, especially during dose escalation, as it worsens nausea significantly.
Potentially, yes — this is important and often missed. Mounjaro can reduce absorption of oral contraceptives, particularly during the first four weeks and after each dose increase. If you're on the combined or progestogen-only pill, use an additional barrier method during these periods or switch to a long-acting reversible method (coil, implant, injection). We'll cover this specifically at your consultation.
You can, and the volume of online prescribing in 2026 is vast. My concern isn't the medication — it's the absence of clinical follow-up. Online services typically rely on self-reported forms and light-touch reviews. That works fine until something goes wrong: a severe side effect, a dose that isn't delivering, a plateau that needs investigation, a decision about stopping. At that point the limitations of arm's-length care become visible. It's your choice — but know what you're trading for convenience.
Oral semaglutide for weight loss is approved in the US and the MHRA is currently reviewing it for the UK — likely available privately in late 2026. Trial data (OASIS-4) showed around 17% weight loss over 64 weeks, broadly comparable to the injection. When it arrives, it will be a reasonable option for needle-averse patients, though the daily dosing schedule requires more discipline than a weekly injection.
Ready for a clinical conversation?
Book a private consultation at Hinchley Medical. We'll review your medical history, run appropriate investigations, and agree — together — whether treatment is the right next step. No pressure, no prescription without assessment.
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This article is written for general information and does not constitute a medical consultation. Mounjaro and Wegovy are prescription-only medicines and must be prescribed by a qualified clinician following a full assessment. Eligibility, risks, and benefits vary between individuals. If you have specific medical concerns, please book a consultation or speak with your GP.