# Tirzepatide: Regulatory Record and Tolerability Reference > Tirzepatide is an FDA-approved dual GIP/GLP-1 receptor agonist. Approval timeline, labeled dosing, tolerability data, and the published clinical trial record — cited and indexed. A read-only reference on the dual GIP/GLP-1 agonist — FDA-approved May 2022 for type 2 diabetes, November 2023 for chronic weight management. Every figure cited. No clinic behind the console. ## > the short version Tirzepatide is a prescription drug approved by the FDA — first for type 2 diabetes in May 2022, then for weight management in November 2023, and later for obstructive sleep apnea in people with obesity. It works by activating two gut hormone receptors at once: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1), both of which help the body regulate blood sugar and appetite after eating. That dual action is why it tends to reduce blood sugar and body weight more than older drugs that target only one of those receptors. In clinical trials, people with obesity lost a mean of 20.9% of their body weight over 72 weeks at the highest dose [1]. In head-to-head trials against a selective GLP-1 agonist, tirzepatide produced greater weight and blood-sugar reductions [2] [3]. The most common side effects are gastrointestinal — nausea, vomiting, diarrhea, constipation — and they are most intense during dose escalation. There are also less common but documented safety signals worth knowing: a significantly increased risk of gallbladder or biliary disease [4], a boxed warning about thyroid C-cell tumors from rodent studies [5], and loss of lean mass alongside fat during rapid weight reduction [6]. What people report — including the downsides — is on [the effects page](/effects). ## What is tirzepatide Tirzepatide is a synthetic 39-amino-acid peptide (a short protein chain) engineered to activate both the GIP receptor and the GLP-1 receptor simultaneously — a dual incretin agonist, sometimes called a "twincretin." It is not a naturally occurring molecule; it is built on the GIP hormone backbone with a C20 fatty-diacid arm attached, which causes it to bind tightly to albumin (a protein in the blood) and gives it an elimination half-life of approximately 5 days [7]. That long half-life is what makes once-weekly dosing feasible. In laboratory signaling assays, tirzepatide engages the GIP receptor more fully than the GLP-1 receptor and shows biased GLP-1 receptor signaling that favors cAMP generation over beta-arrestin recruitment [8]. This imbalanced, biased profile is proposed to contribute to the larger insulin-secretion and weight effects compared with selective GLP-1 agonists. Molecular formula: C225H348N48O68. Molecular weight: 4813.53 Da. CAS: 2023788-19-2. ATC: A10BX16. ## Tirzepatide weight loss SURMOUNT-1 is the pivotal trial in adults with obesity but without type 2 diabetes. In 2539 participants over 72 weeks, once-weekly tirzepatide produced a mean body-weight change of -15.0% at 5 mg, -19.5% at 10 mg, and -20.9% at 15 mg, versus -3.1% with placebo [1]. That 20.9% reduction at the highest dose is among the largest reported for any approved weight-loss agent in a randomized controlled trial. Tirzepatide weight loss is driven primarily by appetite suppression and reduced food intake, both mediated through GIP and GLP-1 receptor signaling at brain circuits governing satiety. Weight reduction occurs independent of whether gastrointestinal adverse events are experienced, based on post-hoc analyses from the SURPASS trials [9]. SUMROUNT-5 randomized 751 adults with obesity to the maximum tolerated dose of tirzepatide or a selective GLP-1 agonist for 72 weeks. Mean weight change: -20.2% with tirzepatide versus -13.7% with the comparator (P<0.001) [3]. ## Tirzepatide vs semaglutide The clearest comparison comes from two trials. SURPASS-2 randomized 1879 adults with type 2 diabetes to tirzepatide (5, 10, or 15 mg once weekly) or semaglutide 1 mg once weekly for 40 weeks. HbA1c reduction: -2.01, -2.24, -2.30 percentage points with tirzepatide versus -1.86 with the comparator — tirzepatide was both noninferior and superior at all doses. Weight reduction was also greater with tirzepatide at all doses (-1.9, -3.6, -5.5 kg treatment differences) [2]. SURMOUNT-5, completed in 2025, is the head-to-head for obesity. At 72 weeks, tirzepatide produced -20.2% body weight versus -13.7% with the selective GLP-1 agonist — a 6.5 percentage-point advantage [3]. The GI tolerability profile is broadly similar between the two classes. Tirzepatide discontinuation due to adverse events is approximately 32% higher versus dulaglutide in one meta-analysis [10], driven by the greater potency and its GI effects during dose escalation. ## Tirzepatide results Across the SURPASS and SURMOUNT programmes, tirzepatide results in type 2 diabetes and obesity are consistent: dose-dependent HbA1c and body-weight reductions that exceed those of selective GLP-1 receptor agonists at comparable doses. Key readouts from the phase 3 programme: - [+] SURMOUNT-1: -20.9% body weight at 15 mg vs -3.1% placebo, 72 weeks, n=2539 [1] - [+] SURPASS-2: HbA1c -2.30 pp at 15 mg vs -1.86 with selective GLP-1 agonist, 40 weeks, n=1879 [2] - [+] SURMOUNT-5: -20.2% vs -13.7% body weight, head-to-head, 72 weeks, n=751 [3] - [note] Cardiovascular, sleep apnea, and liver-fibrosis trials have extended the approved indications beyond glycemia and obesity [11] [12] [13] For the [tirzepatide side effects](/side-effects) and [tirzepatide muscle loss](/muscle-loss) details, the dedicated pages cover those signals fully. Full citations on the [Tirzepatide references](/references) page. --- Regulatory record and trial data — stated plainly. Not a prescription, not a verdict.