The Zepbound Dose Calculator That Actually Remembers You: Units, Next-Step Date, and the Curve Between Shots

Zepbound (tirzepatide) starts at 2.5 mg once weekly and increases in 2.5 mg steps — 5, 7.5, 10, 12.5, up to a 15 mg maximum — with at least 4 weeks between steps, per the FDA prescribing information for Zepbound. For compounded vials, units = (dose in mg ÷ concentration in mg/mL) × 100 on a U-100 syringe, so 5 mg from a 10 mg/mL vial is 50 units. The calculator below projects your next eligible titration date and plots the concentration curve to steady-state. Always confirm your exact dose against your pharmacy label and prescriber before drawing anything up.

This is a planning aid, not a prescription. It models typical dosing and cannot account for your individual plan. Verify every dose and unit figure against your pharmacy label, and talk to your prescriber before changing anything.

🧮 Use the interactive version: open the calculator → — enter your details and get your number in seconds.

Zepbound dosage calculator: what it does

Most Zepbound tools online do exactly one thing. Some convert milligrams to units. Some show a static 2.5-to-15 chart. Some plot a half-life decay curve and stop there. This calculator does the three jobs that actually belong together when you're planning a real dose.

It converts your dose to units for a compounded vial. It schedules — you tell it the day you started your current dose, and it returns the earliest date you'd be eligible to step up. And it visualizes the pharmacokinetic (PK) curve so you can see where tirzepatide sits in your system between weekly shots.

None of that replaces your prescriber or your pharmacy label. Those are the source of truth for what you inject and when. Think of this as a way to see the shape of your plan before your next appointment — and if you want the numbers to stick around instead of vanishing when you close the tab, you can track your next dose and titration step in Tiro.

The Zepbound titration ladder (2.5 → 15 mg chart)

Zepbound follows a fixed dose-escalation schedule. The 2.5 mg starting dose is an initiation dose only — it's meant to ease your gut into the medication, not to drive weight loss on its own. From there, the FDA prescribing information describes stepping up in 2.5 mg increments, holding each dose for at least 4 weeks before the next increase.

Here's the standard ladder:

Recommended maintenance doses are 5, 10, or 15 mg, according to the FDA label and Eli Lilly's Zepbound dosing information. Reaching the 15 mg maximum takes roughly 20 weeks of by-the-book titration. Your prescriber may move slower, hold you longer at a step, or settle you at a dose below 15 mg — all of which is normal.

Next-titration-date projection

The scheduling logic is simple: current-dose start date + at least 28 days = the earliest date you're eligible to step up. That's what the calculator hands back — a personal date, not a generic "week 5 to 8" band.

But eligible is not the same as mandatory. Titration follows tolerability, not the calendar. Nausea is the most common gastrointestinal side effect of GLP-1 and dual GIP/GLP-1 medications, and it typically eases once you've settled on a stable dose. That makes staying at a dose longer than the minimum a completely legitimate, prescriber-guided choice — not a failure. If your gut is still catching up at week four, there's no prize for stepping up on the exact minimum date. For more on reading that signal, see our guide on how to know when to increase your dose.

Zepbound dose in units (compounded vials)

If you're using a compounded tirzepatide vial and a syringe rather than a pre-filled pen, you have to convert your prescribed milligram dose into units. The formula, assuming a standard U-100 insulin syringe:

Units = (dose in mg ÷ concentration in mg/mL) × 100

Worked example: you're prescribed 5 mg, and your vial is 10 mg/mL. That's (5 ÷ 10) × 100 = 50 units. Bump to 7.5 mg from the same vial and you're at 75 units.

The concentration trap: a vial labeled "5 mg/0.5 mL" is not 5 mg/mL — it's 10 mg/mL, because you double the concentration when you halve the volume. Getting this toggle wrong is the single most common way to miscalculate a compounded dose, and it can push your unit count far off. The calculator lets you enter concentration either way, but you are the last line of defense: read your label carefully.

Safety — read before you draw a dose. Brand pre-filled Zepbound pens deliver fixed doses and need no conversion at all; unit math applies only to compounded vials. Compounded tirzepatide is not FDA-approved, and concentrations vary from pharmacy to pharmacy. Verify every figure against your pharmacy's label and your prescriber before injecting. If the label and this tool disagree, the label wins.

Semaglutide in units vs tirzepatide — why the math differs

The units formula is identical for semaglutide, but the inputs aren't. Semaglutide is a different molecule on a different ladder — for Wegovy, the FDA-approved schedule runs 0.25 → 0.5 → 1 → 1.7 → 2.4 mg — and compounded semaglutide vials come in their own set of concentrations. So a "50 units" answer for tirzepatide tells you nothing about semaglutide; you have to plug in that drug's dose and that vial's concentration. If you're on Ozempic or Wegovy, our semaglutide titration schedule guide walks the semaglutide titration schedule in units separately.

The PK curve: reaching steady-state between shots

Tirzepatide has a half-life of about 5 days, according to the FDA prescribing information and StatPearls (NCBI). That long half-life is the whole reason once-weekly dosing works — the drug is still meaningfully present when your next shot comes due.

Because the medication doesn't fully clear between doses, it accumulates. Each weekly injection stacks on the tail of the last one until levels plateau. Steady-state — the point where the amount you inject roughly equals the amount you clear each week — is reached after about 4 to 6 weeks (roughly four to five half-lives), settling at a level meaningfully higher than your first dose alone.

The calculator plots this using a Bateman single-compartment model: each dose rises to a peak, decays across the week, and the next dose lands on top of the residual. Overlay several weeks and you see the staircase climb to a plateau.

This is the part worth sitting with, because it explains the 4-week rule. Each titration step waits at least 4 weeks because that's roughly how long it takes to re-reach steady-state at the new, higher dose. Your tolerability at week three or four reflects the true level you'll be living with — not the lower level from your first shot at that dose. Step up too soon and you're judging tolerability before the new plateau has arrived. Nausea usually eases as you stabilize; if it doesn't, you can log dose-timed side effects and get mitigation tips tied to where you are on the curve. This is educational — how you titrate is your prescriber's call.

From one-off calc to a living titration tracker

Here's the honest limitation of every dose calculator on the web, this one included: it forgets you the moment you close the tab. You re-enter your start date every visit. You do the units math from scratch. Nothing reminds you that your next step is due.

That's the gap Tiro fills. Log your dose once and the calculator becomes a living titration ladder — it remembers your dose history, shows your next-step date, sends a reminder when it's due, and rotates your injection sites so you're not hitting the same spot twice. The web tool is the front door; the tracker is the thing that walks the ladder with you.

Protect your lean mass while you climb. Step-up weeks can be rough on appetite, and when appetite drops it's easy to under-eat protein — which matters, because in some body-composition sub-analyses of GLP-1 weight loss, roughly a quarter to a third of the weight lost has come from lean mass. A practical hedge, supported by protein-during-weight-loss guidance including the ISSN position stand on protein, is a daily protein floor of about 1.2–1.6 g/kg of body weight (versus a general baseline nearer 0.75–0.8 g/kg), with roughly 20–40 g per meal to support muscle. Tiro tracks protein against that floor — a number to reach, not a calorie budget to stay under — so you can hit your daily protein floor (1.2–1.6 g/kg) even on a low-appetite week. Hydration and fiber nudges help smooth the GI adjustment, and you can watch non-scale progress with a 3D body scan instead of trusting the scale alone.

Track your titration in Tiro. This calculator is a one-time snapshot. In the app, one logged dose becomes a living ladder — next-step date, due-date reminder, automatic site rotation. → Tiro — the GLP-1 companion app

Safety, limits, and when to call your prescriber

This tool models typical dosing. Your prescriber may titrate slower than the minimum, hold you at a dose, or cap you below 15 mg — and any of those can be exactly the right plan for you.

A few label-based points worth knowing, all of which route back to your prescriber:

• Missed dose: per the FDA prescribing information and Lilly's dosing guidance, take it within 4 days of the missed dose; if more than 4 days have passed, skip it and resume on your regular day. If you've been off for several weeks, ask your prescriber about restarting at a lower dose rather than jumping back to where you left off.
• The units math is only as good as your label. A compounded vial's concentration can differ from what you assume. Read it every time.
• New or severe symptoms — persistent vomiting, severe abdominal pain, signs of an allergic reaction — are a call-your-prescriber-now situation, not a calculator question.

This article is for information only and is not medical advice — talk to your prescriber. This calculator models typical dosing and cannot account for your individual plan; always verify your dose and units against your pharmacy label before injecting.

FAQ

How do I calculate my Zepbound dose in units? Units = (dose in mg ÷ vial concentration in mg/mL) × 100 on a U-100 syringe. For example, 5 mg from a 10 mg/mL vial = 50 units. Pre-filled Zepbound pens don't need this — they deliver fixed doses. Verify against your pharmacy label.

When can I increase my Zepbound dose? The FDA label allows a step up after at least 4 weeks on your current dose, in 2.5 mg increments. But the decision is tolerability-led and made with your prescriber — eligible on the calendar doesn't mean required.

How long does it take Zepbound to reach steady-state? With a half-life of about 5 days, tirzepatide reaches steady-state after roughly 4 to 6 weeks of weekly dosing, which is part of why each titration step lasts at least 4 weeks.

Is 50 units the same as 5 mg of tirzepatide? Only if your vial is 10 mg/mL. "50 units" depends entirely on your vial's concentration — a 5 mg/0.5 mL vial is 10 mg/mL, and a different concentration changes the unit count. Always check your label.

What's the maximum Zepbound dose? 15 mg once weekly is the maximum; recommended maintenance doses are 5, 10, or 15 mg. Standard titration takes about 20 weeks to reach 15 mg.

What happens if I miss a Zepbound dose? Take it within 4 days of the missed dose; if more than 4 days have passed, skip it and resume on your normal day. If you've been off for several weeks, ask your prescriber about restarting at a lower dose.

Sources

• FDA prescribing information for Zepbound (tirzepatide) — accessdata.fda.gov
• Eli Lilly / Zepbound dosing information — zepbound.lilly.com
• StatPearls, Tirzepatide (NCBI Bookshelf) — ncbi.nlm.nih.gov
• FDA prescribing information for Wegovy (semaglutide) — accessdata.fda.gov
• International Society of Sports Nutrition (ISSN) position stand on protein and exercise