Tirzepatide
Tirzepatide is a first-in-class dual GIP/GLP-1 receptor agonist (Mounjaro/Zepbound) that has demonstrated superior weight loss and glycemic control compared to semaglutide. It activates both incretin pathways simultaneously, producing enhanced metabolic effects.
Evidence Summary
SURMOUNT-1 showed 22.5% mean weight loss at highest dose. SURPASS trials demonstrated superior HbA1c reduction vs semaglutide. SURMOUNT-OSA showed significant improvement in sleep apnea severity. Phase 3 cardiovascular outcomes trial ongoing. UPDATE (September 6, 2026): Tirzepatide is now being tested against AGING endpoints rather than a disease indication. The Moody Longevity Trial at the University of Texas Medical Branch (Galveston; PI Thomas Blackwell), reported in recruitment in August 2026, randomises adults aged 55-70 who already meet clinical criteria for tirzepatide to 24 weeks of weekly tirzepatide followed by 12 weeks off drug, versus observation without medication, with epigenetic-clock measures of biological age and physical function among the outcomes. This is an early signal only: no results have been reported, the comparator is unblinded observation rather than placebo, and the trial is powered for biomarker signal rather than function or clinical outcomes. For context, the only randomised GLP-1 aging-clock result published to date is with semaglutide (approximately 9% slowing of PCGrimAge pace of aging in adults with HIV-associated lipohypertrophy, Nature Communications 2026), which its authors explicitly framed as an early signal in a specific population rather than evidence of rejuvenation. Nothing here establishes that incretin therapy slows human aging.
Evidence Scale
Mechanism of Action
Dual agonism of GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors. GIP receptor activation enhances fat oxidation and energy expenditure in adipose tissue, while GLP-1 reduces appetite and improves insulin secretion. The combined mechanism produces synergistic metabolic improvement beyond single-receptor agonists.
Who Is This For?
BMI ≥30, or BMI ≥27 with comorbidity. Type 2 diabetes inadequately controlled. Patients who have plateaued on GLP-1 monotherapy. Off-label: metabolic optimization.
Protocol & Dosing
Dose
Start 2.5mg weekly for 4 weeks, then escalate: 5mg → 7.5mg → 10mg → 12.5mg → 15mg. Each dose maintained for minimum 4 weeks before escalation. Maximum dose 15mg weekly.
Frequency
Weekly injection
Duration
Ongoing / Long-term
Protocol Summary
Weekly subcutaneous injection with gradual dose escalation over 20+ weeks. Mounjaro indicated for T2D, Zepbound for chronic weight management. Combine with lifestyle modifications and strength training.
Interactions & Precautions
Contraindications
- Personal or family history of medullary thyroid carcinoma
- MEN2 syndrome
- Severe gastrointestinal disease
- History of pancreatitis
- Pregnancy
Potential Risks
- •Thyroid C-cell tumor risk (preclinical)
- •Lean mass loss
- •Gallbladder events
- •Potential pancreatitis
Potential Side Effects
Practitioner Notes
Clinical annotations from Dr. Goel
May offer advantages over semaglutide for patients with significant insulin resistance. Monitor body composition closely — dual agonism may accelerate lean mass loss. GI side effects may be more pronounced during titration. Currently more expensive than semaglutide. Updated September 6, 2026: Expect patients to raise the UTMB Moody Longevity Trial (tirzepatide vs epigenetic clocks and physical function, adults 55-70, in recruitment as of August 2026). Two things to say: results do not exist yet, and the design - unblinded observation comparator, biomarker-powered - means even a positive readout will be hypothesis-generating rather than practice-changing. The clinically important variable to keep watching in this population is unchanged and is not the clock: lean-mass loss with dual incretin agonism in older adults. Continue to monitor body composition, protein intake and resistance training in any patient over 55 on tirzepatide, and do not let an aging-biomarker framing displace sarcopenia risk from the consultation.
Dr. Sanjeev Goel
Chief Medical Officer, Peak Human
Cost & Access
Cost Range
$$$$
Accessibility
Availability varies by location
Sample member
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