| How it works |
Tirzepatide is an incretin-based medicine that activates both GIP and GLP-1 receptors. It helps reduce appetite and cravings, increases feelings of fullness, and can slow gastric emptying, supporting weight loss when combined with diet and activity. |
Semaglutide is a GLP-1 receptor agonist. It acts on appetite centres in the brain to reduce hunger and increase fullness, and can slow gastric emptying, helping you eat less when combined with diet and activity. |
Lipase inhibitor capsule that reduces absorption of some dietary fat in the gut. |
| Licensed use |
Mounjaro (tirzepatide) is officially licensed and approved in the UK for chronic weight management in adults. It is prescribed for weight loss alongside a reduced-calorie diet and increased physical activity. It is also licensed to treat Type 2 Diabetes in the NHS.
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Wegovy (semaglutide) is licensed for:
- Weight management in adults
- Weight management in adolescents
- Cardiovascular risk reduction in adults
- Weight management in relation to Knee Health
Please note Ozempic (semaglutide) is licensed for Type 2 Diabetes only.
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Orlistat is a licensed weight-loss medication in the UK |
| How you take it |
Once-weekly subcutaneous injection using a pre-filled pen. |
Once-weekly subcutaneous injection using a pre-filled pen. |
Capsule with each main meal that contains fat (up to 3/day). |
| Typical use |
Used alongside a reduced-calorie diet and increased activity with weekly dosing and gradual dose increases. In clinical studies, average weight loss was around 15–21% (and up to ~22.5% in some reports), though results vary. |
Used alongside a reduced-calorie diet and increased activity with weekly dosing and gradual dose increases. In clinical studies, average weight loss was around 15-21%, though results vary depending on treatment strength. 1 in 3 patients will acheive 25% weight loss as seen in the STEP UP trial (7.2mg). |
Used alongside a reduced-calorie, lower-fat diet to minimise side effects and support weight loss. Average weight loss is typically more modest (around 5–10% over time), and results vary. |
| Who it may suit |
Adults who prefer once-weekly dosing and are comfortable with injections. |
Adults who prefer once-weekly dosing and are comfortable with injections. |
Adults who prefer tablets and can maintain a lower-fat diet consistently. |
| Common side effects |
Nausea, reflux/indigestion, reduced appetite, constipation or diarrhoea (often settle as dose stabilises). |
Nausea, reflux/indigestion, reduced appetite, constipation or diarrhoea (often settle as dose stabilises). |
Oily stools, urgent bowel movements, flatulence - more likely with high-fat meals. |
| Key cautions |
Not for use in pregnancy/breastfeeding. Do NOT use if you or any family member have a history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). |
Not for use in pregnancy/breastfeeding. Do NOT use if you or any family member have a history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). |
Not for use in pregnancy/breastfeeding; avoid with chronic malabsorption or cholestasis. |
| Storage |
Keep pens refrigerated before first use (do not freeze). Once opened/in use, they can be kept in the refrigerator or at room temperature (up to 28°C) away from heat. Once opened, the pen must be discarded after 30 days. See the patient information leaflet. |
Before opening: keep the pen refrigerated (2°C to 8°C). Keep the pen away from the cooling element inside the fridge
During use: partially used pens must be stored with the needle removed. FlexTouch Pens can be kept for 6 weeks and single dose device pens (7.2mg) can be kept for 4 weeks when stored at a temperature below 30°C or in a fridge (2°C to 8°C) away from the cooling element.
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Store at room temperature away from moisture. |
| Contraception Precautions |
Mounjaro can effect oral contraceptives during dose increases; use added protection as advised or switch to a non-oral method. Please discuss this with your prescriber |
Wegovy® is not anticipated to reduce the effectiveness of oral contraceptives
There are no requirements in the SmPC for women of childbearing age to switch to a non-oral contraceptive method whilst on Wegovy®.
If you wish to become pregnant, you should stop using this medicine at least two months in advance.
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Orlistat does not directly interact with hormonal birth control. However, because orlistat blocks fat absorption and commonly causes severe diarrhoea, it can interfere with how your body absorbs the pill. If you experience severe diarrhoea, your contraceptive pill may become less effective.
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