What it is, who it is for, how it works, and why I upgraded from retatrutide.
| IMPORTANT: This is a personally supervised weight loss journey. My wife is a doctor. Do not attempt any injectable weight loss medication without proper medical supervision and a licensed physician’s guidance. |
I Upgraded. Here Is Why.
After several weeks on retatrutide — an investigational triple-agonist that is still in Phase 3 clinical trials and not yet FDA-approved — my wife and I made the decision to transition to tirzepatide.
The logic was straightforward: retatrutide is still experimental, access is limited and unregulated outside of official trials, and tirzepatide is a fully FDA-approved, commercially available medication with a robust clinical track record that already exceeds most weight loss medications currently on the market.
It was the responsible next step.
And if I am being honest… the logistics of sourcing something unnapproved gets complicated fast.
What Is Tirzepatide?
Tirzepatide is a dual agonist — a medication that mimics two hormones simultaneously: GLP-1 (glucagon-like peptide-1, which suppresses appetite and slows digestion) and GIP (glucose-dependent insulinotropic polypeptide, which regulates insulin and affects fat storage).
It was developed by Eli Lilly and is sold under two brand names: Mounjaro for type 2 diabetes (FDA-approved May 2022) and Zepbound for chronic weight management (FDA-approved November 2023).
It was the most prescribed weight management medication globally in 2025.
It is administered as a once-weekly subcutaneous injection — meaning injected just under the skin, usually in the abdomen, thigh, or upper arm.
Doses start low (2.5mg) and are increased gradually over weeks to minimize side effects, up to a maximum of 15mg weekly.
The pen design is similar to the Ozempic pen — auto-injecting, relatively painless, far more refined than the insulin syringe we used for retatrutide.
Who is it for?
Tirzepatide is FDA-approved for adults with a BMI of 30 or above (classified as obese), or adults with a BMI of 27 or above who also have at least one weight-related condition — such as hypertension, type 2 diabetes, high cholesterol, or obstructive sleep apnea.
I have hypertension and I am managing my weight, so I qualify on both counts.
It is not a drug for people who want to lose five pounds before a reunion. It is for people with a genuine metabolic challenge who are already doing the work and need clinical-grade asistance.
Tirzepatide vs. Retatrutide: The Key Differences
| Tirzepatide (Zepbound / Mounjaro) | Retatrutide (Investigational) | |
| Hormones targeted | GLP-1 + GIP (dual agonist) | GLP-1 + GIP + Glucagon (triple agonist) |
| FDA approval | Yes — approved for obesity and type 2 diabetes | No — still in Phase 3 clinical trials |
| Average weight loss in trials | Up to 22.5% of body weight (SURMOUNT-1, 15mg dose) | Up to 24% in Phase 2; Phase 3 data pending |
| Availability | Commercially available by prescription | Only available in official clinical trials; unverified products are dangerous |
| Administration | Auto-inject pen, once weekly, subcutaneous | Insulin syringe, once weekly, subcutaneous |
| Side effects | Nausea, diarrhea, constipation, vomiting — dose-related | Same gastrointestinal profile, plus possible mild heart rate increase |
What to Expect
In the SURMOUNT-1 Phase 3 trial, participants on the highest 15mg dose lost an average of 48 pounds (about 20.9% of body weight) over 72 weeks.
In the SURMOUNT-5 trial comparing tirzepatide directly against semaglutide (Ozempic/Wegovy), tirzepatide produced 20.2% average weight loss versus 13.7% for semaglutide — a significant clinical differnce.
Side effects are primarily gastrointestinal and tend to ease as the body adjusts to each dose level. Starting at 2.5mg and titrating upward slowly is standard pratice precisely because it keeps those side effects manageable.
I have made the switch. I will report what I experience — the side effects, the appetite changes, the energy levels, and eventually the numbers — honestly and without exaggeration, the same way I have documented the retatrutide journey. Week one of tirzepatide coming soon.
DISCLAIMER
This article is for informational purposes only and does not constitute medical advice. This is a personal weight loss journey conducted under medical supervision. Please consult a licensed physician before beginning any weight loss medication program.
