Tirzepatide

Most peptides in this directory are like promising lab notebooks: interesting ideas, almost no human proof. Tirzepatide is the opposite. It is a finished, road-legal car that passed full crash testing (huge approved trials) and is now sold in dealerships under prescription. Some people buy knock-off versions out of the back of a van online, which carry all the risk and none of the guarantees.

Synthetic peptide that simultaneously activates the GLP-1 and GIP incretin receptors to enhance glucose-dependent insulin release, suppress glucagon, slow gastric emptying and reduce energy intake via appetite-regulating centres in the brain. A fatty-acid modification allows albumin binding and a long half-life suited to weekly subcutaneous injection.

Research contexts. Not proven uses, and not recommendations.

Extensive and high-quality. Multiple large Phase 3 RCTs: the SURPASS programme for type 2 diabetes (including SURPASS-2, which showed superiority over semaglutide on HbA1c and weight) and the SURMOUNT programme for obesity. SURMOUNT-1 showed mean weight loss of roughly 21 to 22 percent at the top dose over 72 weeks, the largest seen for any obesity drug at the time, and SURMOUNT-5 reported head-to-head superiority over semaglutide for weight loss. Further trials cover sleep apnoea, heart failure with preserved ejection fraction, and liver disease (the latter still at Phase 2).

• !Common gastrointestinal side effects: nausea, vomiting, diarrhoea, constipation, the main reason people stop
• !Weight regain is typical after discontinuation; effectively a long-term treatment
• !Risk of acute pancreatitis and gallbladder disease (class effect)
• !Boxed warning for thyroid C-cell tumours (medullary thyroid carcinoma) based on rodent data; contraindicated with a personal or family history of MTC or MEN2
• !Loss of lean muscle mass alongside fat, as with all incretin weight-loss drugs
• !Huge demand has driven a grey market in counterfeit and unlicensed/compounded 'tirzepatide' sold online, carrying serious dosing and contamination risks; only the licensed product (Mounjaro) under prescription is quality-assured
• !Caution/avoidance in pregnancy; may reduce oral contraceptive absorption around dose changes
• !NHS access is rationed and rollout is staged, pushing some people toward private and unregulated online supply

Licensed UK medicine. Tirzepatide (brand Mounjaro, Eli Lilly) holds MHRA marketing authorisation for both type 2 diabetes and chronic weight management (broadly, a BMI of 30 or above, or 27 or above with a weight-related comorbidity). It is a prescription-only medicine (POM). NICE recommends it for weight management (Technology Appraisal TA1026, published December 2024), with a phased NHS rollout that began in primary care in 2025 under tight eligibility criteria. Many patients obtain it privately. Unlicensed or compounded tirzepatide sold online falls outside the regulated supply chain.

• NCT04184622· Phase 3· Completed

  SURMOUNT-1: Tirzepatide in adults with obesity or overweight

  Pivotal obesity trial; roughly 21 to 22 percent mean weight loss at top dose over 72 weeks.

• NCT03987919· Phase 3· Completed

  SURPASS-2: Tirzepatide versus semaglutide added to metformin in type 2 diabetes

  Demonstrated superiority over semaglutide on HbA1c and weight.

• · Phase 3· Completed

  SURMOUNT-OSA: Tirzepatide in obstructive sleep apnoea and obesity

  Reduced apnoea-hypopnoea index; supported an OSA indication.

• · Phase 3· Completed

  SUMMIT: Tirzepatide in heart failure with preserved ejection fraction and obesity

  Outcomes in HFpEF with obesity.

1. 01
   Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) — Jastreboff AM, et al., New England Journal of Medicine (2022)

   Phase 3 obesity RCT; mean weight loss up to roughly 21 to 22 percent over 72 weeks.

2. 02
   Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2) — Frias JP, et al., New England Journal of Medicine (2021)

   Head-to-head superiority over semaglutide on HbA1c and weight.

3. 03
   Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2): a double-blind, randomised, multicentre, placebo-controlled, phase 3 trial — Garvey WT, et al., The Lancet (2023)

   Obesity efficacy in the type 2 diabetes population.

4. 04
   Tirzepatide for Metabolic Dysfunction-Associated Steatohepatitis with Liver Fibrosis (SYNERGY-NASH) — Loomba R, et al., New England Journal of Medicine (2024)

   Phase 2 RCT in MASH; investigational, not a licensed indication.

5. 05
   NICE Technology Appraisal TA1026: Tirzepatide for managing overweight and obesity, National Institute for Health and Care Excellence (2024)

   UK NHS recommendation and eligibility for weight management.