How tirzepatide is dosed: once weekly, low to high
Tirzepatide is a once-weekly injection given under the skin (subcutaneously) in the abdomen, thigh, or back of the upper arm, rotating sites with each dose. According to the FDA prescribing information for both Mounjaro and Zepbound, treatment begins at 2.5 mg once weekly and is increased gradually. This 'start low, go slow' design exists because the most common side effects — nausea, diarrhea, vomiting, and constipation — are usually worst when a dose first goes up, and slower escalation improves tolerability.
The Mounjaro label instructs: start at 2.5 mg once weekly, increase to 5 mg after 4 weeks, and if more effect is needed, increase in 2.5 mg increments after at least 4 weeks on the current dose, to a maximum of 15 mg (10 mg for pediatric patients age 10 and older with type 2 diabetes). The Zepbound label uses the same starting dose and the same 2.5 mg step size and 4-week minimum interval.
Injections can be given at any time of day, with or without food, and the weekly dosing day can be changed as long as doses are at least 3 days (72 hours) apart, per the labels.
Why 2.5 mg is a starter dose, not a therapeutic dose
The 2.5 mg dose is a start-up dose whose purpose is to help the body adjust to the medication, not to deliver full clinical effect. Both FDA labels frame 2.5 mg as the initial 4-week step before increasing to 5 mg, and neither lists 2.5 mg as a maintenance dose.
For Zepbound (weight management), the label's recommended maintenance doses are 5 mg, 10 mg, or 15 mg once weekly; for obstructive sleep apnea, they are 10 mg or 15 mg. For Mounjaro (type 2 diabetes), the prescriber titrates to the dose that achieves glycemic goals, up to the 15 mg maximum. The intermediate strengths 7.5 mg and 12.5 mg are stepping stones used during titration when a patient needs more effect but benefits from a smaller jump.
This is why staying at 2.5 mg long-term is generally not the goal — but whether and when to move up is a clinical decision. A prescriber weighs your response, side effects, and health conditions before every change.
Same molecule, two brands: Mounjaro vs Zepbound dosing
Mounjaro and Zepbound both contain tirzepatide as the only active ingredient, and both come in the identical six strengths: 2.5, 5, 7.5, 10, 12.5, and 15 mg per 0.5 mL. The difference is the FDA-approved use and the titration target, not the drug.
Mounjaro is indicated to improve blood sugar in adults and children 10+ with type 2 diabetes, alongside diet and exercise. Zepbound is indicated for chronic weight management in adults with obesity (or overweight with a weight-related condition) and, as of a 2024–2026 label update, for moderate-to-severe obstructive sleep apnea in adults with obesity. The FDA labels state that tirzepatide products should not be combined with each other or with any other GLP-1 receptor agonist.
Because the molecule and strengths are identical, the titration mechanics (2.5 mg start, 2.5 mg steps, 4-week minimum, 15 mg cap) are the same for both brands. The right maintenance dose differs from person to person and is set by the prescriber.
Missed doses and how to handle a schedule change
The FDA labels give specific guidance for a missed weekly dose, and this is one area where following the label — under your prescriber's direction — matters. Per the Mounjaro and Zepbound prescribing information, if a dose is missed, administer it as soon as possible within 4 days (96 hours) of the missed dose. If more than 4 days have passed, skip the missed dose and take the next dose on the regularly scheduled day.
To change the day of the week you inject, the labels allow it as long as the time between two doses is at least 3 days (72 hours).
These are general label instructions, not personal advice. If you are unsure what to do about a missed or late dose, contact your prescriber or pharmacist rather than doubling up on your own.
LillyDirect vials and pen formats
Tirzepatide is supplied in more than one format. Both brands come as single-dose prefilled pens and single-dose vials, and Zepbound is also available in a multi-dose KwikPen and multi-dose vials introduced in 2025–2026 label updates. The single-dose vials (drawn up with a separate syringe) have been offered as a lower-cost self-pay option, including through Eli Lilly's direct-to-patient LillyDirect pharmacy.
The dose delivered is the same regardless of format — a 5 mg pen and a 5 mg vial both deliver 5 mg. Vials require the patient to measure and inject with a syringe, which introduces room for measurement error, so proper training from the pharmacy or clinician matters.
Prices and program availability change frequently. We compare licensed telehealth providers and their tirzepatide access, but we do not sell, prescribe, or set prices — always confirm current cost and format directly with the pharmacy or provider.
Compounded tirzepatide: not FDA-approved, and the unit-conversion trap
Compounded tirzepatide is not an FDA-approved finished drug. Compounded products are mixed by pharmacies and have not been reviewed by the FDA for safety, effectiveness, or manufacturing quality the way Mounjaro and Zepbound have. After the FDA declared the tirzepatide shortage resolved in late 2024, large-scale compounding of tirzepatide became much more restricted.
The biggest dosing danger with compounded tirzepatide is unit conversion. Brand pens deliver a fixed milligram dose, but compounded vials come in varying concentrations (for example, different mg per mL), and patients are often told to draw up a number of 'units' on an insulin syringe. Because insulin-syringe units measure volume, not milligrams, the same number of units can equal very different tirzepatide doses depending on the vial's concentration. The FDA and state boards have warned about dosing errors and overdoses from this mismatch.
If you use a compounded product, the concentration and dosing instructions come from the compounding pharmacy and prescriber — never assume they match the FDA-label schedule on this page. Confirm the exact milligrams per dose, and never convert 'units' to milligrams yourself.
Who should not follow the standard schedule — and why a prescriber decides
The titration schedule above is the standard FDA-label reference, but it is not automatic. A prescriber may move more slowly, pause a dose increase, or hold you at a lower dose based on side effects, other medications, and your medical history.
Both labels carry a boxed warning about the risk of thyroid C-cell tumors seen in rats; tirzepatide is contraindicated in people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). The labels also warn about pancreatitis, gallbladder disease, acute kidney injury from dehydration, severe gastrointestinal reactions, hypoglycemia (especially when combined with insulin or insulin secretagogues), and hypersensitivity reactions.
Because of these factors, the FDA labels are written for use under a licensed clinician. Do not use this reference schedule to start, adjust, or stop tirzepatide on your own — bring it to your prescriber as a starting point for a conversation.