GLP-1 Weight Loss Treatment: Your Questions Answered
Everything you need to know about Wegovy, Mounjaro, and GLP-1 treatments in the UK — from eligibility and costs to side effects and how to inject.
About GLP-1 Treatments
What are GLP-1 weight loss treatments?
GLP-1 treatments are prescription medications that mimic gut hormones involved in appetite regulation. They reduce hunger, increase feelings of fullness, and slow gastric emptying. The two main treatments available in the UK are Wegovy (semaglutide) and Mounjaro (tirzepatide). Both are administered as weekly subcutaneous injections.
How do GLP-1 treatments work?
GLP-1 (glucagon-like peptide-1) is a hormone your body produces naturally after eating. GLP-1 treatments activate the same receptors, producing three main effects: reduced appetite (you feel less hungry), increased satiety (you feel full sooner and for longer), and slower gastric emptying (food stays in your stomach longer). Mounjaro also targets GIP receptors, a second gut hormone, which may contribute to its higher average weight loss.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) targets GLP-1 receptors only and is NICE-approved for weight management. Mounjaro (tirzepatide) targets both GLP-1 and GIP receptors and showed higher average weight loss in trials (15-21% vs 12-15%), but is not yet NICE-approved for weight loss. See our full comparison.
Are GLP-1 treatments safe long-term?
Semaglutide has been used for type 2 diabetes since 2017 (as Ozempic) with extensive safety data. The SELECT cardiovascular outcomes trial (2023) showed semaglutide actually reduced cardiovascular events by 20%. Tirzepatide has a shorter track record but robust clinical trial data. Both carry known risks (gastrointestinal side effects, rare pancreatitis) which are monitored by your prescriber. Long-term safety studies are ongoing.
Is Ozempic the same as Wegovy?
They contain the same active ingredient (semaglutide) but are different products. Ozempic is licensed for type 2 diabetes at doses up to 2mg. Wegovy is licensed for weight management at a higher maintenance dose of 2.4mg. Both are made by Novo Nordisk. Ozempic should not be used off-label for weight loss when Wegovy is available.
Eligibility
What BMI do I need for weight loss treatment?
Private clinics typically prescribe at BMI 30+ (obesity), or BMI 27+ with a weight-related health condition. NHS criteria are stricter: BMI 35+ (or 32.5+ for some ethnic groups) with at least one comorbidity. Use our BMI calculator and eligibility guide to check.
What age do I need to be?
GLP-1 treatments are licensed for adults aged 18 and over. They are not currently approved for children or adolescents in the UK for weight management, though clinical trials in younger populations are underway.
Who should NOT take GLP-1 treatments?
GLP-1 treatments are contraindicated if you are pregnant or breastfeeding, have a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), or have severe gastrointestinal disease. Caution is advised with type 1 diabetes, severe kidney/liver disease, and eating disorders. Your prescriber assesses all contraindications during consultation.
Are BMI thresholds different for some ethnic groups?
Yes. NICE recognises that health risks associated with excess weight can occur at a lower BMI for people from African Caribbean, Asian, Middle Eastern, and some other ethnic backgrounds. For NHS access, the threshold is 32.5 instead of 35. Private clinics may also apply adjusted thresholds.
Can I get treatment if I've tried dieting and it hasn't worked?
Yes — in fact, most clinics expect that you've already tried lifestyle changes. GLP-1 treatments are intended as an addition to a reduced-calorie diet and increased physical activity, not a replacement. Previous unsuccessful weight loss attempts are not a barrier; they're often part of the eligibility assessment.
Use our BMI calculator and eligibility guide to check your potential eligibility.
Cost and Access
How much do GLP-1 treatments cost privately?
Wegovy starts from around GBP 100/month at the starter dose, rising to GBP 205-229/month at the maintenance dose (2.4mg). Mounjaro starts from around GBP 177/month, rising to GBP 325-370/month at the maximum dose (15mg). Prices vary by clinic. Use our cost calculator to compare.
Can I get GLP-1 treatment on the NHS?
Wegovy is available through NHS specialist weight management services under NICE TA875. However, access varies by area and waiting lists can be long. Mounjaro is not yet NICE-approved for weight loss. See our NHS vs Private guide for details.
Is weight loss treatment covered by health insurance?
Most UK private health insurance policies do not cover weight loss medication. Some insurers may cover specialist consultations or assessments but not the medication itself. Check with your insurer for their specific policy on obesity treatment.
Do all clinics charge the same?
No. Prices vary significantly between clinics, and what's included also differs. Some include coaching, apps, and aftercare in their price. Others offer a more basic service at a lower cost. Compare clinics to see full breakdowns.
Do I pay more as my dose increases?
Yes. Higher doses contain more active ingredient and cost more. During the escalation phase (first 4-5 months), you'll be on lower, cheaper doses. Plan for the maintenance dose cost as your ongoing monthly expense.
Side Effects
What are the most common side effects?
Nausea is the most commonly reported side effect, particularly during dose escalation. Other common effects include diarrhoea, constipation, vomiting, abdominal pain, and headache. Most improve as your body adjusts. See our complete side effects guide.
How long do side effects last?
Most gastrointestinal side effects are worst during the first 1-2 weeks at each new dose level and improve within 4-6 weeks. The gradual dose escalation schedule is specifically designed to minimise side effects. If they persist, your prescriber may slow the escalation or adjust your dose.
Are there serious risks I should know about?
Serious side effects are rare but include pancreatitis, gallbladder problems, and kidney issues (usually from dehydration). Both treatments carry a boxed warning about medullary thyroid carcinoma (from animal studies). Your prescriber screens for risk factors before prescribing. Seek immediate help for severe abdominal pain, difficulty breathing, or signs of allergic reaction.
Can I drink alcohol while on GLP-1 treatment?
There's no absolute contraindication to alcohol, but many people find their alcohol tolerance decreases on GLP-1 treatments. Alcohol can worsen nausea and gastrointestinal side effects. It also adds empty calories that work against your weight loss goals. If you drink, do so in moderation and be aware of reduced tolerance.
Using the Treatment
How do I inject GLP-1 treatments?
Both Wegovy and Mounjaro come as pre-filled pens with hidden needles — you don't see or handle the needle. You inject subcutaneously (under the skin) into your abdomen, thigh, or upper arm. Your clinic will provide injection instructions. Most people find it straightforward after the first time.
Where on my body do I inject?
Recommended injection sites are the abdomen (at least 5cm from the navel), the front of the thigh, or the upper arm. Rotate injection sites each week to avoid irritation. Avoid injecting into areas that are bruised, tender, or scarred.
What if I miss a dose?
For both treatments: if you miss a dose and your next scheduled dose is more than 2 days away, take the missed dose as soon as possible. If your next dose is due within 2 days, skip the missed dose and continue with your regular schedule. Never take two doses to make up for a missed one.
How long do I need to take GLP-1 treatments?
GLP-1 treatments are designed for long-term use. Clinical evidence shows that weight regain is common after stopping — the STEP 1 extension study showed participants regained approximately two-thirds of their lost weight within a year of stopping. Your prescriber will discuss a long-term plan with you.
Can I stop and restart treatment?
Yes, but you may need to restart at a lower dose and go through dose escalation again to minimise side effects. Stopping and restarting frequently is not recommended. If you're considering stopping, discuss it with your prescriber first — they may suggest alternatives like dose reduction.
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Sources
- NICE Technology Appraisal TA875: Semaglutide for managing overweight and obesity (June 2023)
- Wilding JPH et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." NEJM 2021; 384:989-1002
- Jastreboff AM et al. "Tirzepatide Once Weekly for the Treatment of Obesity." NEJM 2022; 387:205-216
- Lincoff AM et al. "Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes." NEJM 2023; 389:2221-2232
- MHRA Summary of Product Characteristics: Wegovy (semaglutide), Mounjaro (tirzepatide)
- NHS — Obesity: identification, assessment and management (CG189)
- General Medical Council — Prescribing unlicensed medicines