Tirzepatide: Dual-Receptor Mechanism, Dosing, and Results

What tirzepatide is

Tirzepatide is a dual agonist: it activates both the GLP-1 receptor and the GIP receptor. GLP-1 reduces appetite and slows gastric emptying; GIP is a second incretin hormone that appears to improve insulin sensitivity and how the body handles fat. Hitting two pathways instead of one is the structural reason tirzepatide behaves differently from single-receptor drugs. It is the active molecule in Mounjaro and Zepbound.

How it compares on weight loss

In its pivotal obesity trial, tirzepatide produced up to about 21% mean body-weight reduction at the 15 mg dose over 72 weeks. In a head-to-head trial against semaglutide, tirzepatide produced more weight loss (roughly 20% versus 14% mean), with a larger share of participants reaching the 15% and 20% thresholds. On current evidence it is the more powerful weight-loss molecule on average, though "on average" matters: the right drug for any individual depends on labs, budget, and tolerance. See our full tirzepatide vs semaglutide comparison.

Tirzepatide dosing chart

Tirzepatide is a once-weekly subcutaneous injection that steps up roughly every 4 weeks. The standard titration is:

• Weeks 1-4: 2.5 mg once weekly (starting dose, not therapeutic)
• Weeks 5-8: 5 mg once weekly
• Weeks 9-12: 7.5 mg once weekly
• Weeks 13-16: 10 mg once weekly
• Weeks 17-20: 12.5 mg once weekly
• Week 21 onward: 15 mg once weekly (maximum maintenance)

Maintenance is commonly 5, 10, or 15 mg depending on response and tolerance. Not everyone needs to reach 15 mg. The goal is the lowest dose that delivers steady progress without intolerable side effects, and your provider will hold or slow the schedule if needed.

Side effects

The side-effect profile is broadly similar to semaglutide because both slow the gut: nausea, constipation, diarrhea, and reflux, worst in the weeks after a dose increase and usually improving with time. Gallbladder issues and pancreatitis are uncommon but real (report severe, persistent abdominal pain immediately). Tirzepatide carries the same boxed warning regarding thyroid C-cell tumors and is not appropriate with a personal or family history of medullary thyroid carcinoma or MEN2.

Compounded vs brand-name

Brand-name tirzepatide is expensive without coverage. Compounded tirzepatide, prescribed when clinically appropriate, is typically billed by the pharmacy at cost and generally runs somewhat higher per month than compounded semaglutide because tirzepatide is the newer, more complex molecule. As with all compounding, availability tracks FDA shortage status and regulation, and a responsible prescriber tells you when that changes.

The KAYU approach

Tirzepatide protocols at KAYU start with the same full metabolic panel as any GLP-1 protocol, because the drug is the easy decision and the underlying metabolic picture is the important one. Your provider builds the protocol with a muscle-preservation plan and a defined maintenance and off-ramp strategy, not a prescription and a wish of luck.