N° 003 · The Directory

Tirzepatide

Active ingredient in Mounjaro and Zepbound. Dual GLP-1 + GIP agonist with a quiet liver story.

S-Tier Weight Loss FDA-approved

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What it does - plain English

Tirzepatide is the active ingredient in Mounjaro (the brand approved for type 2 diabetes) and Zepbound (the brand approved for weight loss). It is a once-weekly injection. It mimics two of your gut's natural hormones at the same time: GLP-1 (a hormone your gut releases after eating that signals fullness - the same one Ozempic mimics) and GIP (another gut hormone that helps the body handle sugar and fat).

The dual mechanism is why it tends to outperform Ozempic on weight loss in head-to-head studies. When two systems are signaling "stop eating and burn fat" instead of one, the effect compounds.

There is also a quieter story. It appears to reduce liver scarring (fibrosis - the process where damaged liver tissue turns to scar tissue over time) in people with fatty liver disease, especially in those who have not used a GLP-1 before. Most weight-loss media coverage still has not caught up to this finding.

Status

S-tier for weight loss in 2026. The SURMOUNT-1 trial showed average 22.5% weight loss at the highest dose over 72 weeks in adults with obesity who did not have diabetes. That number is unusual. Most drugs in this space land at 5-10%. The SURPASS trials showed strong A1C (a measure of average blood sugar over roughly three months) control for diabetes. Real-world results match the trial numbers more closely than most drugs do.

The catch: side effects are real. Nausea and GI (gastrointestinal - stomach and gut) distress are common for the first 4-8 weeks, especially as the dose ramps up. The cost without insurance is high enough that access, not efficacy, is the main limiting factor for most people.

Legal status

Tirzepatide is FDA-approved as Mounjaro for type 2 diabetes (May 2022) and Zepbound for obesity (November 2023). These are the same molecule with different brand names and approved indications.

Compounded versions - made by compounding pharmacies (specialty pharmacies that mix drugs to order) during an FDA-declared shortage - were widely available through 2024 and into early 2025. The FDA's shortage declaration ended in late 2024, and again in early 2025, each time restricting how much compounding pharmacies could legally produce and ship. Telehealth services still ship compounded tirzepatide in some states. The legality varies by state and by how aggressively the FDA is enforcing at a given moment.

If you are buying compounded tirzepatide, ask for a COA (Certificate of Analysis - the lab report proving the bottle contains what they say it contains, at the concentration listed).

Where to source

Three paths exist. None is perfect for everyone.

Traditional pharmacy with insurance - usually requires a type 2 diabetes diagnosis or a BMI (body mass index) of 30 or above for coverage. If you qualify, this is the cleanest path. No quality concerns. No legal gray area.
Telehealth services - services like Eden Health, SkinnyRx, Yucca Health, and Fridays Health write prescriptions and either send them to a standard pharmacy or work with compounding pharmacies to fill them. Most require a short intake form and a video or async consult. Pricing varies widely.
Compounding pharmacies via telehealth - cheaper than brand-name, but legally complicated given the shifting shortage status. Always ask for a COA before buying. No COA, no buy.

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Two studies worth reading

Weight loss benchmark

Jastreboff et al., "Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)," NEJM

The headline trial. 2,539 adults with obesity but without diabetes saw average weight loss of 22.5% at the highest dose over 72 weeks. This is the obesity-weight-loss benchmark every other GLP-1 is now compared against.

Liver disease readout

Loomba et al., "Tirzepatide for Metabolic Dysfunction-Associated Steatohepatitis with Liver Fibrosis (SYNERGY-NASH)," NEJM

190 adults with biopsy-confirmed MASH (fatty liver disease that scars the liver over time) participated. After 52 weeks of tirzepatide, 51-62% had MASH resolution without worsening fibrosis. The liver story most weight-loss media still has not fully covered.

From the Editor

My take: tirzepatide is the runaway success story of the GLP-1 era. The data is unusually consistent between trials and real-world use. Side effects are real for the first month or two, but they tend to be manageable and dose-dependent. If someone in your family is weighing their options, this is the conversation worth having with their doctor first.

What I would tell my dad: do not buy tirzepatide off Instagram. If you can get insurance to cover Mounjaro or Zepbound, try that first. If insurance won't cover it - common without a diabetes diagnosis - telehealth with a real prescription beats going to a research peptide vendor. If you go the compounding route, ask for a COA on every batch. If the vendor can't produce one, walk away.

What I would skip: any "tirzepatide blend" with sermorelin or other peptides mixed in. One molecule, one bottle. Mixed compounded products are where quality problems hide, and there is no pharmacokinetic (how your body absorbs and processes a drug) rationale for most of these combinations. The blend upsell is a margin play, not a science play.

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Last reviewed · 2026·05·04 · Status reviewed weekly