# Tirzepatide: The Dual GIP/GLP-1 Weight-Management Trial Record > Tirzepatide produced mean weight loss of -20.9% at 15 mg over 72 weeks in SURMOUNT-1. An independent digest of the SURPASS and SURMOUNT clinical trial record. An independent editorial digest of the phase 3 clinical trial record — what the studies measured, how they were designed, and what remains open. Not a clinic. Not a vendor. ## The short version Tirzepatide is a once-weekly injectable medicine approved by the FDA for type 2 diabetes (May 2022) and for weight management in adults with obesity (November 2023). It works by activating two gut hormone receptors — GIP and GLP-1 (hormones your gut releases after meals to signal fullness and help control blood sugar) — with a single molecule. In clinical trials, it produced the largest average weight reductions ever measured in a randomized trial: roughly one in five pounds of body weight lost over 72 weeks at the highest dose, in people without diabetes. It also outperformed another weight-loss medicine, semaglutide, head-to-head in a direct comparison trial. The main side effects are gastrointestinal — nausea, constipation, diarrhea — and are most pronounced during dose escalation. There is a boxed warning about thyroid tumors based on animal data; people with a history of certain thyroid cancers or a related genetic syndrome should not use it. This site is an independent editorial digest of the published research. It is not a clinic, and no product is sold here. ## What the Tirzepatide trial record has established Tirzepatide (International Nonproprietary Name: tirzepatide; development code LY3298176) is a 39-amino-acid synthetic peptide engineered from the native GIP (glucose-dependent insulinotropic polypeptide) sequence, with a fatty-diacid arm attached via a glutamic acid linker that confers high albumin affinity and an approximately five-day half-life [1]. That structural design supports once-weekly subcutaneous dosing and is the same fatty-acid modification strategy used across the long-acting incretin class. The preclinical and phase 1 proof-of-concept work established two things: the molecule activates both GIP and GLP-1 receptors, and — when administered chronically to mice — it reduced body weight and food intake more than a selective GLP-1 receptor agonist alone [1]. A phase 1 programme in 142 human subjects confirmed pharmacokinetics consistent with once-weekly dosing and showed reductions in fasting glucose and body weight versus placebo [1]. What followed was one of the most comprehensively characterized phase 3 programmes for a metabolic drug. The SURPASS trials (five core studies, roughly 14,000 participants with type 2 diabetes) tested it against placebo, basal insulin, and other active comparators. In SURPASS-2 — a 40-week open-label head-to-head against semaglutide 1 mg in 1,879 adults with type 2 diabetes — tirzepatide reduced HbA1c (the standard blood-sugar marker) by 2.01, 2.24, and 2.30 percentage points at the 5, 10, and 15 mg doses, versus 1.86 percentage points with semaglutide. Weight reductions were also greater: treatment differences of -1.9, -3.6, and -5.5 kg at the three doses [3]. The SURMOUNT programme shifted the lens to obesity. SURMOUNT-1 — a 72-week phase 3 double-blind trial in 2,539 adults without diabetes — is the study that defined the scale of the effect: mean weight changes of -15.0%, -19.5%, and -20.9% at 5, 10, and 15 mg versus -3.1% with placebo [4]. A 2025 head-to-head against semaglutide (SURMOUNT-5, 751 adults without diabetes) found -20.2% with tirzepatide versus -13.7% with semaglutide over 72 weeks [5]. A 2025 Japanese population trial (SURMOUNT-J) confirmed the effect across an Asian cohort, with -21.1% at 15 mg versus 20% placebo response [9]. Beyond weight and glycemia, the clinical programme has extended into heart failure with preserved ejection fraction (SUMMIT trial) [13], obstructive sleep apnea (SURMOUNT-OSA) [12], and metabolic dysfunction-associated steatohepatitis (SYNERGY-NASH) [14]. These readouts have broadened the evidence base beyond the weight-management lens, though weight management remains the best-characterized indication. For further reading on [tirzepatide weight loss](/weight-loss), the SURMOUNT results page covers every primary endpoint in the obesity programme. The [Tirzepatide research](/research) page covers the full SURPASS/SURMOUNT record and the mechanism. [Tirzepatide effects](/effects) — including what people report and what the safety literature documents — is a separate page. ## A note on this site This is an independent editorial project that summarizes the published peer-reviewed literature on tirzepatide. The domain name references telehealth as a context — tirzepatide is frequently discussed in telemedicine settings — but this site is not a telehealth provider, does not connect users with clinicians, and does not sell or facilitate access to any product. Every claim on this site cites a specific published study listed on the [Tirzepatide references](/references) page. --- An austere editorial record of what the SURMOUNT and SURPASS trials measured — not a clinic, not a prescription, not a vendor.