Tirzepatide

The most effective GLP-1-class medication currently approved, activating both GIP and GLP-1 receptors. Trial participants lost up to 21% of body weight — the highest of any approved option.

What tirzepatide is Tirzepatide is a “twincretin”: a single molecule that activates both the GLP-1 receptor and the GIP (glucose-dependent insulinotropic polypeptide) receptor. The dual action appears to produce more weight loss than GLP-1 activation alone, with a side-effect profile that is similar or — in many patients — slightly gentler at comparable weight loss. ## The evidence - SURMOUNT-1 (NEJM, 2022): adults without diabetes lost an average of 20.9% of body weight on the 15 mg dose over 72 weeks (16.0% on 5 mg), versus 3.1% on placebo. Over a third of participants on the top dose lost 25% or more. - SURMOUNT-5 (2025): in the first large head-to-head trial, tirzepatide produced about 47% more relative weight loss than semaglutide 2.4 mg (roughly 20% vs. 14% average loss). - SURMOUNT-OSA: approved indication for moderate-to-severe obstructive sleep apnea in adults with obesity, after large reductions in apnea events. ## Forms you will encounter | Form | What it is | FDA-approved? | | --- | --- | --- | | Zepbound | Brand pens/vials, approved for weight management and OSA | Yes | | Mounjaro | Brand pens, approved for type 2 diabetes (off-label for weight) | Yes | | Compounded injectable | Pharmacy-prepared, prescribed when a clinician documents need for a customized formulation | No | | Sublingual / rapid-dissolve | Under-the-tongue compounded form; different absorption, not dose-equivalent | No | ## Semaglutide or tirzepatide? Head-to-head, tirzepatide produces more average weight loss. But semaglutide has the proven cardiovascular-event reduction (SELECT trial), a longer real-world track record, and is sometimes cheaper or better covered. Plenty of people respond excellently to either; tolerability is individual. The full comparison lives at semaglutide vs. tirzepatide. ## Side effects in brief Same class profile as semaglutide: nausea, constipation, diarrhea, and fatigue concentrated around dose escalations; rare pancreatitis and gallbladder risks; the same rodent thyroid C-cell boxed warning and contraindications (MTC/MEN 2 history, pregnancy). Injection-site reactions are slightly more commonly reported than with semaglutide. ## Cost reality Zepbound lists around $1,086/month; LillyDirect sells single-dose vials to cash payers for roughly $349–$499/month. Compounded tirzepatide typically runs $250–$450/month. Coverage details and savings strategies are in the cost guide.