# Tirzepatide A weekly injection that acts like two gut hormones at once, and the best-selling medicine in this book. In a head-to-head trial it beat semaglutide on weight loss. Also called: Mounjaro, Zepbound Source page: https://peplogue.com/peptides/tirzepatide/ Updated: 2026-10-22. Not medical advice. ## How it works - Where it acts: GIP and GLP-1 receptors in the pancreas, gut, fat tissue and brain. - What it changes: The same effects as GLP-1 drugs, with added GIP signalling. How much each part contributes is still debated. - What people notice: Less hunger and steady weight loss over months. Nausea, diarrhoea or constipation are common early on. ## What the evidence shows - **Weight loss in obesity**: Proven. SURMOUNT-1: about 21% average loss at 72 weeks on the top dose, or 22.5% among people who stayed on it. - **Type 2 diabetes**: Proven. Approved as Mounjaro. - **Obstructive sleep apnea with obesity**: Proven. Approved in the US in December 2024. In SURMOUNT-OSA, breathing pauses fell by 25 to 29 an hour, against about 5 on placebo. - **Cardiovascular risk in type 2 diabetes**: Proven. In SURPASS-CVOT it matched dulaglutide (hazard ratio 0.92) without clearly beating it. FDA added heart and stroke risk reduction to the Mounjaro label in August 2026. - **Heart failure with obesity**: Supported. SUMMIT (731 people): worsening heart failure or cardiovascular death fell 38%. - **Fatty liver disease (MASH)**: Supported. In a phase 2 trial MASH cleared in 44% to 62% of people, against 10% on placebo. ## Side effects and risks - serious: Boxed warning for thyroid C-cell tumors, seen in rodents. - serious: Pancreatitis and gallbladder disease. - common: Nausea, diarrhea, vomiting and constipation, mostly while the dose is rising. - common: The US label warns that the contraceptive pill may be less reliable for four weeks after starting and after each dose increase, and advises a backup method. The EU label asks for no change. - common: Muscle is lost along with fat, and weight returns after stopping. - common: Low blood sugar when combined with insulin or sulfonylureas. Who should avoid it: Pregnancy, medullary thyroid cancer or MEN 2 in you or your family, and past pancreatitis unless a specialist agrees. ## How it is taken Weekly injection under the skin, starting at 2.5 mg and rising by 2.5 mg no faster than every four weeks to a maintenance dose of 5, 10 or 15 mg. A prescriber sets the schedule. ## Legal status - United States: undefined. Mounjaro for diabetes and Zepbound for weight and sleep apnea. LillyDirect self-pay in October 2026: $299 to $449 a month if each refill comes within 45 days, up to $699 otherwise. Compounded versions are still sold, though large-scale compounding lost its legal basis when the shortage ended. - European Union: undefined. Mounjaro, for type 2 diabetes and weight management. - Spain: undefined. Mounjaro KwikPen is marketed (CIMA). Not SNS-funded for any use; the pricing commission rejected it (Dec 2025). Paid in full on private prescription. - Germany: undefined. Mounjaro pen on sale, Rx only. GKV pays only for type 2 diabetes; weight loss is self-pay (lifestyle exclusion), upheld by a court in 2025. - France: undefined. Mounjaro sold since Nov 2024, liste I. 65% for type 2 diabetes (set regimens) and, since 15 Jun 2026, severe obesity (BMI 35+ with illness, or 40+). - Italy: undefined. Mounjaro: classe A with Nota 100 for type 2 diabetes. For weight management it is classe C (C-nn): prescription needed, you pay. Cannot be bought online. - Netherlands: undefined. Mounjaro: insured under conditions for type 2 diabetes (Bijlage 2). Not insured for weight loss alone; Zorginstituut review not expected to finish before 2027. - United Kingdom: undefined. Mounjaro. NHS access through GP practices is being phased in by BMI and health conditions; otherwise a private prescription through a registered pharmacy. - Canada: undefined. Mounjaro, and Zepbound for weight management. - Australia: undefined. Mounjaro, including for long-term weight management. Not subsidized, so a private prescription. ## Questions people ask **Are Mounjaro and Zepbound the same drug?** Yes. Both are tirzepatide from Eli Lilly. In the US, Mounjaro is the diabetes brand and Zepbound the brand for weight and sleep apnea; in the EU and Australia, Mounjaro is also licensed for weight management. **Is tirzepatide better than semaglutide for weight loss?** In a head-to-head trial, tirzepatide beat semaglutide on weight. In SURMOUNT-1, average loss was about 21% at 72 weeks on the top dose, or 22.5% among people who stayed on it. **Does Mounjaro make the birth control pill less effective?** The US label warns that the contraceptive pill may be less reliable for four weeks after starting and after each dose increase, and advises a backup method. The EU label asks for no change. **What are the side effects of tirzepatide?** Nausea, diarrhea, vomiting and constipation are common, mostly while the dose is rising. Serious risks include pancreatitis, gallbladder disease and a boxed warning for thyroid C-cell tumors seen in rodents. Muscle is lost along with fat, and weight returns after stopping. **How much does Zepbound cost without insurance?** The maker's US self-pay price in October 2026 was $299 to $449 a month if each refill came within 45 days, and up to $699 otherwise. Compounded versions are still sold, though large-scale compounding lost its legal basis when the shortage ended. ## Sources - AJMC: FDA expands tirzepatide label for cardiovascular risk (28 Aug 2026): https://www.ajmc.com/view/fda-expands-tirzepatide-label-to-reduce-cardiovascular-risk-in-t2d - Eli Lilly: second-quarter 2026 results: https://www.sec.gov/Archives/edgar/data/0000059478/000005947826000077/q226lillysalesandearningsp.htm - EMA: Mounjaro product page: https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro - NHS South West London: GLP-1 medicines policy (June 2026): https://www.southwestlondon.icb.nhs.uk/wp-content/uploads/2026/07/Interim-Policy-Statement-GLP-1-based-meds-update-June-2026.pdf - Lilly: Zepbound self-pay prices: https://zepbound.lilly.com/coverage-savings - Finnrick: vendor test counts: https://www.finnrick.com/