How Each Drug Works: The Science Made Simple
Mounjaro (tirzepatide)
- A dual agonist: it activates both GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) receptors. This two-pronged approach enhances insulin response, curbs appetite, slows digestion, and can lead to considerable weight loss.
- Approved for type 2 diabetes (and for weight management in the UK since late 2023)
- Average 23% weight loss after 12 months
- May affect oral contraceptives, so additional precautions will be needed during treatment.
- It may also affect certain medicines you take for other conditions, and I will advise you about that if it applies to you based on the medicines you have told me that you take.
Wegovy (semaglutide)
- A GLP-1 receptor agonist only. It mimics the hormone GLP-1 to regulate blood sugar, reduce appetite, and slow gut motility.
- Contains the same active ingredient as Ozempic
- It’s approved for weight loss (and some cardiovascular and liver conditions)
- Average 18% weight loss after 12 months
- Great choice for significantly reducing the risk of heart attacks and strokes if you have any kind of existing cardiovascular disease (e.g. angina, previous heart attack or stroke)
- Good choice if you have risk factors for cardiovascular disease such as high blood pressure, high cholesterol, or type 2 diabetes.
Key Comparative Insight
Mounjaro generally delivers greater average weight loss (around ~23%) compared to Wegovy’s ~18% at current doses, but Wegovy’s upcoming 7.2 mg dose may match or even exceed that, with early trial data showing ~21% loss, and a third of patients losing more than 25%
Pricing: UK Private Market Spotlight
Mounjaro
As of 1 September 2025, UK private prices for the highest dose surged from ~£122 to between £270–£330 per month, a dramatic increase of up to 170%
Wegovy
Remains considerably more affordable, with private monthly fees typically ranging between £85–£240, depending on dose and provider
- Novo Nordisk has confirmed no planned price increases in the UK
Switching: Tips for a Seamless Transition
Dosage Alignment: Healthcare providers can match your current Mounjaro dose to an equivalent Wegovy dose (e.g., if you experienced side effects on Mounjaro, they may advise stepping down slightly on Wegovy initially)
| Mounjaro Dose | Starting Wegovy Dose |
|---|---|
|
2.5 mg
|
Re-titrate from 0.25 mg |
|
5 mg |
0.5 mg |
|
7.5 mg |
0.5 mg |
|
10 mg |
1 mg |
|
12.5 mg |
1 mg |
|
15 mg |
1.7 mg |
| Wegovy Dose | Starting Mounjaro Dose |
|---|---|
|
0.25 mg
|
Re-titrate from 2.5 mg |
|
0.5 mg |
5 mg |
|
1 mg |
7.5 mg |
|
1.7 mg |
10 mg |
|
2.4 mg |
12.5 mg |
- Avoiding Dual Use: Never take both medications simultaneously doing so increases side effect risks without improving results.
- Side Effects & Adjustment: Both drugs share similar side effects (nausea, bowel changes, tiredness). Many people who tolerated Mounjaro well experience smooth transitions, especially when starting on the right Wegovy dose.
- Expect a Plateau? Some people notice a temporary pause in weight loss when switching, but most continue losing steadily within a few weeks.
Lifestyle & Long-term Success
Neither drug offers a “magic bullet”, meaningful results depend heavily on diet, hydration, exercise, and solid injection technique. Missing these basics can limit effectiveness and amplify side effects like fatigue or bloating.
Summary Table:
| Factor | Mounjaro UK (Private) | Wegovy UK (Private) |
|---|---|---|
|
Mechanism
|
Dual GIP + GLP-1 |
GLP-1 only |
|
Average Weight Loss |
23% |
18% (upcoming 7.2 mg ~21%) |
|
Private Cost |
£270–£330/month (before ~£122) |
£85–£240/month |
|
Price Trend |
Recent hike (+170%) |
Stable pricing |
|
Side Effects |
Similar to Wegovy |
Similar; possibly fewer injection site reactions |
|
Special Benefits |
Strong weight loss |
Heart & kidney protection, doesn’t affect oral contraceptives or thyroid medications. |
Final Thoughts
If you’re privately paying and feeling the financial pinch from Mounjaro’s recent price hikes, Wegovy is a compelling, cost-effective alternative, especially with equivalent dosing available and promising new formulations on the horizon.
Still, whichever path you choose, your health journey matters most. You can speak with our pharmacist to create a tailored transition plan that keeps your momentum going.
