The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
5mg Mounjaro — UK Weight Management Explained
The 5mg dose is Mounjaro's first maintenance step in the UK weight management pathway. After starting at 2.5mg for four weeks, patients typically move to 5mg once weekly as their body adjusts to tirzepatide. This dose activates both GIP and GLP-1 hormone pathways, which may help reduce appetite and support weight management alongside lifestyle changes. Our BMI calculator and GLP-1 weight loss calculator can help you understand your current health context and whether prescription weight management might be relevant for your needs according to NHS guidance on healthy weight UK standards.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How 5mg Works in the UK Treatment Plan
The 5mg Mounjaro dose represents the first maintenance level in the tirzepatide escalation schedule used across UK specialist weight management services. Patients remain on 5mg for a minimum of four weeks before any increase, allowing the body to adapt to the medication's effects on appetite regulation and fullness signalling.
Key facts about 5mg dosing:
- Given as a once-weekly injection via pre-filled KwikPen
- Each KwikPen contains 4 doses (4 weeks' supply)
- Administered on the same day each week
- Can be stored at room temperature for up to 30 days after first use
- Commonly held for 4–12 weeks depending on individual response and tolerability
Clinical data suggests patients on 5mg in the SURMOUNT trials experienced average weight loss of approximately 15% of body weight over 72 weeks, though individual results vary significantly based on diet, activity, and personal metabolism.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
5mg Side Effects and What to Expect
Most patients report gastrointestinal side effects at the 5mg dose, particularly in the first 2–4 weeks. Nausea is very common but often improves as the body adjusts. Keeping hydrated, eating smaller meals, and avoiding fatty foods can help manage symptoms.
Common side effects at 5mg include:
- Nausea or feeling sick
- Diarrhoea or constipation
- Stomach discomfort or indigestion
- Loss of appetite
- Injection site reactions (redness or mild bruising)
If you experience persistent vomiting, severe abdominal pain, or signs of allergic reaction, contact your GP or prescriber immediately. Our weight converter and healthy weight UK reference tools can help track your progress safely.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is 5mg the standard Mounjaro dose in the UK?
5mg is the first maintenance dose, not the standard long-term dose. Patients start at 2.5mg, move to 5mg after four weeks, then may escalate to 7.5mg, 10mg, 12.5mg, or 15mg depending on tolerability and response. Most UK patients eventually use higher doses, but 5mg is where the maintenance journey begins.
How much weight loss is typical on 5mg Mounjaro?
Clinical trials showed patients on 5mg achieved average weight loss of around 15% of body weight at 72 weeks, alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly — some lose less, some more. Your prescriber can discuss realistic expectations for your situation.
Can I stay on 5mg long-term or will my dose increase?
Your prescriber will assess your response at each stage. If 5mg is controlling appetite well and you're experiencing acceptable side effects, you may stay at this dose. If further weight loss is needed or side effects are manageable, your prescriber may recommend escalating to 7.5mg after another four weeks.
Does 5mg Mounjaro work for type 2 diabetes as well as weight loss?
Mounjaro is licensed for weight management in the UK, not diabetes (that's a different indication). If you have type 2 diabetes and are considering tirzepatide, speak to your GP or diabetes specialist about eligibility through NHS guidance. Our NHS health advice section covers weight management in relation to metabolic health.
Where can I get a 5mg Mounjaro prescription in the UK?
In the UK, Mounjaro is available through NHS tier 3 specialist weight management services (via GP referral, though waiting lists vary by region) or through private online prescribing following a clinical assessment. Your prescriber will determine the correct starting dose for your health needs.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.