Get your exact tirzepatide
injection volume, in seconds.
Free, no signup. Works for Mounjaro, Zepbound, and compounded vials. See your mL, syringe units, and escalation schedule, all in one place.
What Is a Tirzepatide Dosage Calculator?
A tirzepatide dosage calculator converts your prescribed milligram dose into the exact milliliter volume you need to draw into a syringe. If you're using compounded tirzepatide from a vial rather than a pre-filled Mounjaro or Zepbound pen, you need this calculation every week before you inject.
The formula is straightforward: divide your prescribed dose (in mg) by your vial's concentration (in mg/mL). A 5 mg dose from a 10 mg/mL vial means you draw 0.5 mL. From a 5 mg/mL vial, you'd draw 1.0 mL. Getting this right matters: drawing too little delivers an underdose, and drawing too much risks side effects.
This calculator also tracks your dose escalation schedule. The FDA-approved protocol for tirzepatide increases the dose by 2.5 mg every four weeks as tolerated. Knowing where you are in that schedule helps you stay on track and communicate clearly with your prescriber.
Whether you're a patient managing your own compounded injections, a caregiver helping someone else, or just trying to double-check a dose before you inject, use the calculator above to get the exact numbers you need.
Tirzepatide Dosage Guide: What Patients Need to Know
The Standard Dose Escalation Schedule
Tirzepatide follows a gradual dose escalation to minimize GI side effects. The FDA-approved schedule: 2.5 mg (wk 1–4) → 5 mg (wk 5–8) → 7.5 mg (wk 9–12) → 10 mg (wk 13–16) → 12.5 mg (wk 17–20) → 15 mg (wk 21+). The SURMOUNT-1 clinical trial showed patients at 15 mg lost an average of 22.5% of body weight.
For a complete breakdown, see our week-by-week tirzepatide dosage schedule guide.
Compounded vs. Brand-Name Tirzepatide
Mounjaro and Zepbound are FDA-approved pens manufactured by Eli Lilly, pre-filled with no volume calculation needed. Compounded tirzepatide is produced by 503A or 503B pharmacies in vials at 5 or 10 mg/mL, and that's where our calculator is essential. Learn more in our compounded tirzepatide vs. Mounjaro comparison.
Injection Site & Technique
Inject subcutaneously into the abdomen (2+ inches from navel), outer thigh, or upper arm. Rotate sites weekly to prevent lipohypertrophy. For step-by-step instructions, read our tirzepatide injection technique guide.
Storage and Handling
Store at 36–46°F (2–8°C), use within 28 days, never freeze. See our tirzepatide storage and handling guide.
Who Should Use This Calculator?
This tool is built for anyone using compounded tirzepatide from a vial. That includes:
- Patients on compounded tirzepatide who receive vials from a 503A or 503B pharmacy and draw their own dose weekly.
- Mounjaro and Zepbound users who want to track their escalation schedule or understand when their next dose increase is due.
- Caregivers helping a patient verify the correct dose before administering.
- Patients switching concentrations (e.g., moving from 5 mg/mL to 10 mg/mL). See our vial concentration guide.
This calculator is for informational use only. Always confirm your dose with your prescriber. New to injections? Start with our step-by-step injection guide and side effects management guide.
Patient Guides
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Frequently Asked Questions
The FDA-approved tirzepatide titration schedule starts at 2.5 mg once weekly for 4 weeks, then increases by 2.5 mg every 4 weeks as tolerated. The progression is: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg (maximum). Your prescriber may keep you at a lower dose if you are experiencing side effects or achieving satisfactory results before reaching the maximum.
Injection volume (mL) = Prescribed dose (mg) ÷ Vial concentration (mg/mL). For example, if your dose is 5 mg and your vial is 10 mg/mL, you inject 0.5 mL. If your vial is 5 mg/mL, you inject 1.0 mL. Always verify the concentration on your vial label and double-check with your pharmacist before injecting.
Brand-name tirzepatide (Mounjaro and Zepbound) comes in pre-filled auto-injector pens with pre-set doses, so no volume calculation is needed. Compounded tirzepatide comes in vials at various concentrations (commonly 5 or 10 mg/mL) and requires drawing the correct volume with a syringe. Compounded versions are typically used when brand-name pens are unavailable due to shortages or when cost is a factor.
Most patients use a 1 mL insulin syringe with a 29–31 gauge needle for subcutaneous injection. On a standard U-100 insulin syringe, 100 units = 1 mL, so 0.5 mL = 50 units and 0.1 mL = 10 units. This calculator shows your dose in both mL and insulin syringe units for easy measurement. Your pharmacist can recommend the appropriate syringe for your vial concentration.
Tirzepatide is injected subcutaneously (under the skin) into the abdomen (at least 2 inches from the navel), the outer thigh, or the upper arm. Rotate injection sites each week to prevent lipohypertrophy (fatty lumps from repeated injections in the same spot). Inject into a pinched fold of skin at a 45-degree angle for the abdomen or a 90-degree angle for sites with more subcutaneous tissue.
If you miss a dose and it is within 4 days of your scheduled day, take it as soon as you remember, then resume your regular weekly schedule. If more than 4 days have passed, skip the missed dose and take your next dose on the regularly scheduled day. Do not take two doses in the same week. Contact your prescriber for guidance if you miss multiple doses or are unsure about timing.
Mounjaro and Zepbound auto-injector pens are pre-filled with fixed doses and do not require volume calculation; you simply select the dose and inject. This calculator is primarily for patients using compounded tirzepatide from a vial who need to draw the correct volume into a syringe. The escalation schedule information applies to both brand-name and compounded tirzepatide.
By itself, tirzepatide has a low risk of hypoglycemia. However, patients taking tirzepatide alongside insulin or sulfonylureas (like glipizide or glimepiride) have a significantly higher risk of low blood sugar. If you take these medications together, your prescriber will likely reduce your insulin or sulfonylurea dose when starting tirzepatide. Monitor blood glucose closely during the first weeks of treatment.