Question 1

What is the starting dose of tirzepatide?

Accepted Answer

The starting dose is 2.5 mg once weekly via subcutaneous injection for the first 4 weeks. This is a tolerability dose, not a treatment dose for weight loss or HbA1c. After 4 weeks the dose escalates to 5 mg, the first true maintenance dose. Further escalation occurs in 2.5 mg increments at minimum 4-week intervals up to 15 mg weekly, based on individual tolerance.

Question 2

What is the highest dose of tirzepatide / Zepbound?

Accepted Answer

The maximum FDA-approved dose is 15 mg once weekly for both Mounjaro and Zepbound. This is also the highest dose that was studied in the SURPASS and SURMOUNT trials. In SURMOUNT-1 the 15 mg arm averaged −22.5% body weight loss at 72 weeks, only modestly higher than the 10 mg arm at −21.4%. Many users do well at 10 mg without escalating further.

Question 3

What is tirzepatide's half-life?

Accepted Answer

Tirzepatide's half-life is approximately 5 days (about 120 hours). This is what supports once-weekly dosing. With weekly injections, blood levels build up over about 4 weeks before reaching steady state at roughly 1.6× a single dose. That is why each ladder step lasts at least 4 weeks — the body needs that time to fully adjust.

Question 4

How do you convert tirzepatide mg to insulin units?

Accepted Answer

Insulin syringes use U-100 markings, where 1 mL = 100 units. The conversion depends on the concentration after reconstitution. The cleanest setup is a 40 mg vial with 2.0 mL BAC water, giving 20 mg/mL. At that concentration: 2.5 mg = 12.5 units, 5 mg = 25 units, 7.5 mg = 37.5 units, 10 mg = 50 units, 12.5 mg = 62.5 units, 15 mg = 75 units. For any other vial-and-water pairing, use the PepPal calculator .

Question 5

How much weight can you lose on tirzepatide?

Accepted Answer

In SURMOUNT-1 (NEJM 2022, 2,539 adults with obesity), the 15 mg arm averaged −22.5% body weight loss at 72 weeks, the 10 mg arm −21.4%, and the 5 mg arm −16.0%. In the head-to-head SURMOUNT-5 trial (NEJM 2025), tirzepatide produced −20.2% weight loss vs −13.7% for semaglutide. These are population averages over 72 weeks, not promises for any individual.

Question 6

How do you reconstitute tirzepatide?

Accepted Answer

For a 40 mg lyophilized vial, add 2.0 mL of bacteriostatic water for a 20 mg/mL solution. Inject the water slowly down the inside vial wall, swirl gently (do not shake), and refrigerate at 2–8 °C. Use within 28 days. For other vial sizes, see the reconstitution table above or use the PepPal calculator .

Question 7

Is tirzepatide FDA-approved?

Accepted Answer

Yes. Mounjaro was FDA-approved in May 2022 for type 2 diabetes. Zepbound was approved in November 2023 for chronic weight management and in December 2024 for moderate-to-severe obstructive sleep apnea with obesity. Tirzepatide is the first and only FDA-approved dual GIP/GLP-1 receptor agonist.

Question 8

What is the difference between Mounjaro and Zepbound?

Accepted Answer

Mounjaro and Zepbound contain the same active drug, tirzepatide, in the same titration ladder. The only differences are the indication on the label and the packaging. Mounjaro is approved for type 2 diabetes. Zepbound is approved for obesity and for OSA with obesity. The dose schedule (2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg weekly) is identical.

Question 9

What are the most common tirzepatide observed effects?

Accepted Answer

Gastrointestinal effects dominate: nausea (17–22%), diarrhea (13–16%), vomiting (6–10%), decreased appetite (7–9%), and indigestion (~7%). Most are mild to moderate, hit hardest during dose escalation, and improve at stable doses. Discontinuation due to observed effects ranged from ~5% at 5 mg to ~10% at 15 mg in trials. Tirzepatide also carries a boxed warning for thyroid C-cell tumors and is contraindicated with MTC or MEN 2 history.

Question 10

How does tirzepatide compare to semaglutide?

Accepted Answer

Tirzepatide is a dual GIP/GLP-1 agonist; semaglutide activates GLP-1 only. In the head-to-head SURMOUNT-5 trial (NEJM 2025), tirzepatide produced −20.2% weight loss vs −13.7% for semaglutide at 72 weeks. In SURPASS-2 (T2D), all tirzepatide doses showed superior HbA1c and weight reductions vs semaglutide 1 mg. GI observed effect profiles were broadly similar.

Question 11

What if I miss a tirzepatide dose?

Accepted Answer

Per the Mounjaro and Zepbound prescribing information, take the missed dose as soon as possible if it is within 4 days (96 hours). After that window, skip it and resume on the next regularly scheduled day. Do not double up. The day of the week can be changed as long as the last dose was at least 3 days earlier.

Question 12

Who should not take tirzepatide?

Accepted Answer

Avoid tirzepatide if you have a personal or family history of medullary thyroid carcinoma or MEN 2 (boxed warning), a history of pancreatitis, severe gastrointestinal motility disease, or known hypersensitivity to tirzepatide. It is not recommended in pregnancy and is not a substitute for insulin in type 1 diabetes. Stop at least 2 months before a planned pregnancy because of the long half-life.

Question 13

What vial sizes are available for research-grade tirzepatide?

Accepted Answer

Research-grade lyophilized tirzepatide is commonly sold in 5 mg, 10 mg, 15 mg, 40 mg, and 60 mg vials. The 40 mg vial is the most popular because it covers the full 2.5–10 mg ladder with compact math when reconstituted with 2.0 mL of BAC water (20 mg/mL).

Question 14

How is reconstituted tirzepatide stored?

Accepted Answer

Store the reconstituted solution in the refrigerator at 2–8 °C (35.6–46.4 °F) and use within 28 days. Do not freeze it — freezing damages the peptide. Protect from light. Use bacteriostatic water (0.9% benzyl alcohol) for multi-dose vials; sterile water only if the entire vial will be used in one session.

Question 15

Is compounded tirzepatide the same as branded Mounjaro or Zepbound?

Accepted Answer

Compounded tirzepatide is a tirzepatide product mixed by a compounding pharmacy, not the FDA-approved Lilly pen. During the 2023–2024 shortage, large-scale compounding was permitted; outside that shortage, access is restricted and depends on state and federal compounding rules. Compounded products vary in concentration, formulation, and quality. They are not bioequivalent to Mounjaro or Zepbound by FDA standards.

Question 16

Can tirzepatide be taken orally?

Accepted Answer

Not currently. As of June 2026 there is no FDA-approved oral tirzepatide. Oral incretin therapies do exist for semaglutide (Rybelsus), but tirzepatide is only FDA-approved as a subcutaneous injection. "Tirzepatide tablets" sold online are not FDA-approved formulations.

Phase	Reference amount	Units / volume
Weeks 1–4	2.5 mg	100 units (1.0 mL) × 1 injection
Weeks 5–8	5 mg	100 units (1.0 mL) × 2 injections
Weeks 9–12	7.5 mg	100 units (1.0 mL) × 3 injections
Weeks 13–16	10 mg	100 units (1.0 mL) × 4 injections

Phase	5 mg 2 mL water	10 mg 2 mL water	15 mg 2 mL water	30 mg 3 mL water
Weeks 1–4	100 u 1.00 mL	50 u 0.50 mL	33 u 0.33 mL	25 u 0.25 mL
Weeks 5–8	100 u 1.00 mL	100 u 1.00 mL	67 u 0.67 mL	50 u 0.50 mL
Weeks 9–12	100 u 1.00 mL	75 u 0.75 mL	100 u 1.00 mL	75 u 0.75 mL
Weeks 13–16	100 u 1.00 mL	100 u 1.00 mL	67 u 0.67 mL	100 u 1.00 mL

Tirzepatide.

Calculated volume reference

Cited protocol & reconstitution guide

Reconstitution by vial size