lookindex

Tirzepatide

Also known as Zepbound, Mounjaro

The strongest weight loss drug currently approved in this index. Same trade-offs as semaglutide: common side effects, a prescription, and long-term use.

Information only. Not medical advice. Talk to a doctor before you start, stop or change anything.

What people claim

  • Beats semaglutide for weight loss
  • Safe for anyone who wants to lean out
  • Compounded versions are the same drug

What the evidence shows

  • In SURMOUNT-1, adults with obesity lost up to 20.9% of body weight over 72 weeks at the top dose, against 3.1% on placebo.[1]
  • The head-to-head claim holds up. In SURMOUNT-5, it led to 20.2% weight loss against 13.7% for semaglutide.[2]
  • As with semaglutide, trials enrolled people with obesity or overweight plus a related health problem, not healthy-weight people chasing definition.[1]
  • Compounded products are not the same as the approved drug. FDA does not review them for safety, effectiveness or quality.[4]

Known risks

  • Nausea, diarrhoea, vomiting and constipation are common.[3]
  • Boxed US warning: thyroid C-cell tumours in rats. Not for people with a personal or family history of medullary thyroid cancer or MEN 2.[3]
  • Label warnings include severe stomach reactions, kidney injury, gallbladder disease, pancreatitis, low blood sugar and suicidal thoughts.[3]
  • Hair loss was reported in about 5% of people against 1% on placebo, and more often in women (7.1%) than men (0.5%).[3]
  • Compounded versions: FDA had more than 730 adverse event reports by 31 May 2026.[4]
  • Fake pens circulate. Report any you find to your regulator.[5]

Reported side effects

Moderated user reports are not open yet, so nothing is shown here. They will be labelled as unverified personal accounts.

Legal status

A summary, not legal advice. Rules change, and sport bans are separate.

United States

Prescription

FDA approved. Compounded versions are not FDA approved and are not reviewed for safety or quality.

United Kingdom

Prescription

Licensed. MHRA warns against pens bought online.

Australia

Prescription

Approved by TGA.

European Union

Prescription

Authorised through the European Medicines Agency.

Sources

  1. 1.SURMOUNT-1 trialNew England Journal of Medicine, 2022
  2. 2.Tirzepatide as compared with semaglutide for the treatment of obesityNew England Journal of Medicine, 2025
  3. 3.US prescribing information for tirzepatideUS FDA
  4. 4.FDA's concerns with unapproved GLP-1 drugs used for weight lossUS FDA
  5. 5.MHRA seizes illegal medicines worth almost £45m in 2025MHRA UK

Profile last checked 7 Nov 2026.