Tirzepatide.
The strong one.

The short answer

Tirzepatide is a dual agonist. It acts on the GIP receptor as well as the GLP-1 receptor, and that second target is the structural difference behind its results. It is FDA approved as Mounjaro for type 2 diabetes and as Zepbound for chronic weight management. In the SURMOUNT-1 trial, participants on 15 mg weekly lost 20.9 percent of body weight on average over 72 weeks, the largest average produced by any approved weight loss medicine to date.

What the trials show

• SURMOUNT-1 — 72 weeks, 15 mg weekly plus lifestyle support, 20.9 percent mean body weight loss. The 10 mg and 5 mg arms produced less, so dose and result move together.
• Head to head — a randomized trial comparing tirzepatide directly against semaglutide for weight management reported greater average weight loss on tirzepatide. Stated qualitatively, because that is what the comparison supports: on averages, the dual agonist came out ahead.
• Diabetes first — the Mounjaro approval for type 2 diabetes came before the weight management approval, and blood sugar lowering is strong enough that many endocrinologists reach for it early.
• Spread around the average — a mean of 20.9 percent contains people who lost far more and people who lost little. There is no test that predicts which group you land in before starting.
• Beyond weight — tirzepatide has also been studied in obstructive sleep apnea associated with obesity, which is part of why it is treated as a medical therapy rather than a cosmetic one.

The compounded question

Same story as semaglutide, same honest version. While tirzepatide was on the FDA shortage list, compounding pharmacies were permitted to make versions of it and a large telehealth market formed around that allowance. The shortage was resolved, brand supply recovered, and through 2025 and 2026 the FDA moved to end most of that activity and acted against mass production and mass marketing of non-approved GLP-1 products.

So a cheap tirzepatide program today is not automatically illegitimate, but it is no longer standard practice. Narrow patient-specific compounding can still be lawful in defined circumstances. Ask the clinic to name the pharmacy, state its license type, and explain the legal basis for compounding your prescription. Anyone shipping vials without a prescription is not a pharmacy.

Dosing in practice

A physician sets the dose. What follows is the labeled pattern, described so you can read a prescription rather than write your own.

Dosing starts at 2.5 mg once weekly for four weeks, which is a starting dose rather than a treatment dose, then increases in 2.5 mg steps at intervals of at least four weeks toward 5, 10 or 15 mg weekly depending on response and tolerance. Brand pens deliver a fixed dose. Compounded vials arrive as liquid or as powder that must be reconstituted, and the arithmetic between milligrams, milliliters and insulin syringe units is where people go wrong. Confirm your math with the prescriber before the first injection.

Run the reconstitution math

What it costs

Brand-name Zepbound or Mounjaro without insurance is typically advertised at roughly 1000 to 1350 dollars per month, with manufacturer savings programs and direct-to-patient vial pricing often bringing that down substantially. Where compounded programs remain lawful, telehealth clinics typically advertise 200 to 400 dollars per month. Insurance coverage for weight management depends on the plan and usually requires prior authorization, while coverage for type 2 diabetes is far more common.

Side effects and risks

• Common — nausea, vomiting, diarrhea, constipation, indigestion, reduced appetite and fatigue, most of it clustered around dose increases and easing with time.
• Uncommon but serious — pancreatitis, gallbladder disease including stones, and kidney injury from dehydration after prolonged vomiting.
• Boxed warning — thyroid C-cell tumors occurred in rodents. The label contraindicates use in anyone with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2.
• Muscle loss — a meaningful share of the weight lost is lean mass. Resistance training and adequate protein belong in the plan from week one.
• Stopping — trial follow-up shows substantial weight regain after discontinuation, which is why this is framed as long-term treatment of a chronic condition.

Legal and FDA status

Tirzepatide is an approved prescription drug in the United States under the Mounjaro and Zepbound brands, and it is prescription-only in every form, compounded included. There is no lawful over-the-counter tirzepatide and no research-use vial that a person may legally inject. Independent testing of gray-market vials has repeatedly found wrong doses and impurities, which is the concrete hazard behind the discount.

Which one to compare it to

The only fair rival is semaglutide, since both are approved, both are peptides, both are weekly injections and both have large trials behind them. The differences that matter in practice are average effect size, side effect tolerance, insurance coverage and price, and they do not all point the same direction.

See the head to head

The doctor path

A licensed physician reviews your weight history, medical history, medications and labs, decides whether a GLP-1 medicine fits and which one, writes a prescription that a US pharmacy fills, and monitors the titration. That visit is also what catches the histories that rule tirzepatide out, which no vendor will ever ask about.

Talk to a doctor

Questions people ask

Sources: NEJM — SURMOUNT-1 tirzepatide · FDA on compounded GLP-1s · NEJM — STEP 1 semaglutide · PubMed — tirzepatide literature