Tirzepatide Dosage Guide for Weight Loss

Tirzepatide is a first-in-class dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist developed by Eli Lilly. It is FDA-approved as Mounjaro® for type 2 diabetes and Zepbound® for chronic weight management.

The SURMOUNT-1 trial demonstrated mean weight loss of 22.5% at the 15 mg dose over 72 weeks — the highest weight loss ever achieved with a pharmaceutical agent in a phase 3 trial. Tirzepatide's dual-receptor mechanism provides additive metabolic benefits beyond single-receptor GLP-1 agonists like semaglutide.

Tirzepatide follows a mandatory dose escalation schedule to optimize gastrointestinal tolerability:

In SURMOUNT-1, weight loss was dose-dependent: 15.0% (5 mg), 19.5% (10 mg), and 22.5% (15 mg). The minimum therapeutic dose is 5 mg; 2.5 mg is for titration only.

Tirzepatide is administered once weekly by subcutaneous injection. Its extended half-life of approximately 5 days supports weekly dosing.

Administration day: Choose a consistent day of the week. The injection can be given at any time, regardless of meals. If the injection day needs to change, ensure at least 3 days (72 hours) have passed since the last dose.

Dose escalation: Increase the dose no sooner than every 4 weeks. If significant GI side effects occur at a new dose level, remain at the current dose for an additional 4 weeks before re-attempting escalation.

Branded tirzepatide (Mounjaro®, Zepbound®) is available in pre-filled auto-injectors. For compounded lyophilized tirzepatide:

• Step 1: Sterilize vial stoppers with alcohol swabs.
• Step 2: Add the appropriate volume of BAC water. For a 30 mg vial, add 3 mL to yield 10 mg/mL.
• Step 3: Direct the stream along the glass wall. Allow to dissolve without agitation.
• Step 4: Gently swirl. The solution should be clear to slightly opalescent.
• Step 5: Refrigerate at 2–8°C. Use within 28 days.

Inject subcutaneously into the abdomen, thigh, or upper arm using a 29–31 gauge insulin syringe. Rotate injection sites each week.

Side effects are predominantly gastrointestinal and dose-dependent:

• 2.5–5.0 mg: Nausea (12–24%), diarrhea (12–17%), decreased appetite. Generally mild.
• 7.5–10.0 mg: Nausea prevalence increases to 20–30%. Vomiting in approximately 5–9% of subjects. Constipation reported.
• 12.5–15.0 mg: In SURMOUNT-1, nausea occurred in 31% at 15 mg. Most GI events were mild-to-moderate and occurred during dose escalation.

Treatment discontinuation due to adverse events occurred in 4.3–7.1% of subjects across dose groups, compared to 2.6% with placebo.

Tirzepatide carries a boxed warning regarding thyroid C-cell tumors based on rodent studies. Contraindicated in individuals with MTC or MEN 2 history.

Monitor for pancreatitis (discontinue if suspected), gallbladder events, and hypoglycemia when combined with insulin or secretagogues. Tirzepatide should not be used with other GLP-1 or GIP receptor agonists. Use only under medical supervision.