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
Is Wegovy Safe For Weight Loss?
Wegovy (semaglutide) is a prescription-only weekly weight loss injection that has been safety-tested in clinical trials and approved by UK regulators for weight management. Like all medications, it carries both benefits and risks that vary between individuals. This guide explains what the evidence shows about Wegovy's safety profile, how it works, and what you should consider before discussing it with your GP or prescriber. Individual results and side effects vary significantly, and Wegovy is prescribed only after a clinical assessment.
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 Safe Is Wegovy? What Clinical Evidence Shows
Wegovy (semaglutide) has been assessed for safety through the STEP clinical trials, which involved thousands of participants over 68 weeks. The trials showed that Wegovy is generally well-tolerated, though side effects were common—particularly nausea, diarrhoea, and constipation, especially when starting or increasing doses. Most side effects were mild to moderate and often improved over time as the body adjusted.
The key safety finding: Wegovy is a prescription-only medicine, which means it is only prescribed following a clinical assessment by a licensed prescriber who evaluates your individual health profile, medical history, and whether the weekly weight loss injection is appropriate for you. This assessment is crucial—it screens for contraindications like pancreatitis risk, gallbladder disease, or certain medications that may interact with semaglutide. The prescriber also monitors your dose escalation carefully, starting at 0.25 mg and increasing gradually over weeks before reaching the maintenance dose of 2.4 mg.
Serious side effects are rare but can occur. These include severe stomach pain (possible pancreatitis), gallbladder problems, serious allergic reactions, and changes in heart rate or vision. If you experience any of these, seek urgent medical attention immediately.
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.
Important Safety Considerations and Who Should Not Use Wegovy
Wegovy is not suitable for everyone. You should not take it if you are pregnant, planning pregnancy, or breastfeeding—semaglutide may affect foetal development. Do not use Wegovy if you have a history of medullary thyroid cancer or multiple endocrine neoplasia type 2 (MEN2), or if you are allergic to semaglutide or any ingredients in the pen.
If you take oral contraceptives, add a barrier method or switch to non-oral contraception for 4 weeks after starting Wegovy and 4 weeks after each dose increase—semaglutide may reduce medication absorption. If you take diabetes medications like sulphonylureas or insulin, your prescriber may adjust your dose.
Wegovy works best alongside a reduced-calorie diet and increased physical activity. Try our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and use our weight converter to track your progress in stone, kilograms, or pounds. Your GP can provide personalised safety advice based on your individual health.
- 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 Wegovy safer than other weight loss methods?
Wegovy has clinical trial data showing safety over 68 weeks. Compared to bariatric surgery, it carries fewer risks, though side effects are common initially. Compared to lifestyle changes alone, Wegovy adds medication risk but can help when lifestyle changes alone haven't worked. Individual safety depends on your health profile—your prescriber assesses this.
What are the most common side effects of Wegovy in the UK?
The most common side effects are nausea, diarrhoea, vomiting, and constipation—affecting many people, especially in the first 4 weeks. Most improve as your body adjusts. Other common effects include indigestion, headache, fatigue, and dizziness. Side effect severity varies greatly between individuals.
Can I use Wegovy long-term? Is it safe to stay on it?
Clinical trials tested Wegovy for 68 weeks. Longer-term safety data is still emerging. Some people continue it for weight maintenance after reaching their goal; others stop after initial weight loss. Your prescriber will discuss duration based on your response and health profile.
Does Wegovy cause pancreatitis or gallbladder problems?
Serious pancreatitis or gallbladder complications are rare but can occur. Tell your prescriber immediately if you experience severe abdominal pain spreading to your back, or pain in the upper stomach area. People with a history of pancreatitis or gallbladder disease may not be suitable candidates.
How does Wegovy compare to Mounjaro for safety?
Both are prescription-only injections with similar side effect profiles—nausea, diarrhoea, constipation common initially. Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is GLP-1 only. Clinical trial data shows both are generally safe in approved doses, but individual tolerability varies. Your prescriber assesses which is safer for your specific health situation.
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.