Tirzepatide dosage chart: titration, units and vial math

The label is written as a staircase. Weeks 1 to 4 are 2.5 mg once weekly, described as a tolerance step rather than a treatment dose. After 4 weeks the dose can rise to 5 mg. Every further increase is 2.5 mg and must wait at least 4 weeks: 7.5, then 10, then 12.5, then 15 mg. The maintenance doses studied in SURMOUNT-1 were 5, 10 and 15 mg; 7.5 and 12.5 mg exist as intermediate steps for people who need a slower climb.

The schedule is a ceiling on speed, not a target. The label says increases happen as tolerated, and the trials show a dose response where 5 mg still produced about 15 percent average weight loss over 72 weeks. Plenty of people stop at 5 or 7.5 mg because that is where appetite control and side effects balance for them. Reaching 15 mg is not required and not always better for a given person.

Mounjaro, the diabetes version, follows the same 2.5 mg steps to the same 15 mg maximum. Compounded and grey-market tirzepatide has no label, and people using it almost always copy the Zepbound schedule, which is why the chart below is organized around those steps.

Tirzepatide has a half-life of about 5 days. A drug with that half-life takes roughly four to five half-lives to reach steady state after a dose change, which works out to about 3 weeks. The label waits 4 weeks so the body is at the full effect of the current step before deciding whether to go up. Moving faster means stacking a new increase on top of a level that is still rising.

The 4 weeks also give the gut time to adapt. Nausea, fullness and reflux are driven by slowed gastric emptying, and that effect is strongest right after each increase and settles as the stomach adjusts. In the trials, most GI complaints were mild to moderate and clustered in the escalation period. People who climb faster than the label, which happens on the grey market because there is no pharmacist to say no, report more of the side effects that make them quit.

If a step causes persistent nausea, the compound page's protocol note and the general pattern in the trials point the same way: hold the current step another month rather than pushing through. The label allows going up no sooner than 4 weeks, which means 8 or 12 weeks at a step is entirely within it.

It depends on the concentration, and only on the concentration. A U-100 insulin syringe holds 100 units per mL, so 1 unit is 0.01 mL. The volume for a dose is the dose in mg divided by the concentration in mg per mL; multiply by 100 to get units. At 5 mg/mL, 2.5 mg is 0.5 mL, which is 50 units. At 10 mg/mL it is 0.25 mL, or 25 units. At 20 mg/mL it is 0.125 mL, or 12.5 units.

The live chart above runs that math for every step. At 10 mg/mL, the most common concentration for a 10 mg vial mixed with 1 mL, the ladder is 25, 50, 75, 100, 125 and 150 units. The 12.5 and 15 mg steps exceed a 1 mL syringe at that concentration and need two draws or a stronger mix. At 20 mg/mL the whole ladder fits in one draw, but the 2.5 mg step is a 12.5 unit draw that is easy to misread on a syringe marked in 2 unit increments.

The error that sends people to urgent care is reading the units for one concentration and drawing them from a vial at another. Fifty units from a 20 mg/mL vial is 10 mg, four times the starting dose. Always start from the label on the vial you are holding, and run it through the calculator if there is any doubt. Our insulin syringe units chart explains the syringe side in more detail.

Concentration is the vial amount divided by the water added. The standard amounts on the tirzepatide page all land on 10 mg/mL: 10 mg with 1 mL, 15 mg with 1.5 mL, 30 mg with 3 mL and 60 mg with 6 mL. That makes the units ladder the same whichever vial you bought, which is the main reason to pick it. The only limit is the vial itself: a 60 mg vial may not physically hold 6 mL, in which case 3 mL gives 20 mg/mL.

Adding more water lowers the concentration and makes small doses easier to measure. A 10 mg vial with 2 mL is 5 mg/mL, and the 2.5 mg step becomes a 50 unit draw that is hard to get wrong. Adding less water raises the concentration and saves syringe volume at the top steps. Neither choice changes the dose; it changes only the number on the syringe.

Once mixed, the compound page says to keep it refrigerated at 2 to 8 C and use it within 4 weeks. A 10 mg vial covers four weeks at 2.5 mg or two weeks at 5 mg, so the first vial is usually used up before it expires. A 60 mg vial at a 2.5 mg dose would last 24 weeks, far past the 4 week window, which is one reason larger vials suit higher maintenance doses. The reconstitution guide covers the mixing steps and the water choice.

The trials give a dose response: about 15 percent average loss at 5 mg, 19.5 percent at 10 mg and 20.9 percent at 15 mg over 72 weeks in SURMOUNT-1. The jump from 5 to 10 mg buys more than the jump from 10 to 15 mg, and side effects rise with each step. That shape is why a lot of people settle at 5, 7.5 or 10 mg rather than climbing to the maximum.

The practical signal people use is appetite. If food noise is quiet and weight is moving at a reasonable rate on the current step, there is no trial-based reason to increase. If appetite returns and loss stalls after a month or two, the next step is the usual response. The compound page frames the right dose as the lowest one that keeps appetite controlled with tolerable side effects, and the label's as-tolerated wording supports that.

Maintenance also means long term. In the SURMOUNT-4 withdrawal study, people switched to placebo after 36 weeks regained much of the lost weight within a year. Dose reduction for maintenance is being studied and is the subject of our GLP-1 microdosing article; as of now, no trial supports a reduced maintenance dose.

The Zepbound label says a missed dose should be taken as soon as possible within 4 days (96 hours) of the scheduled time. If more than 4 days have passed, skip it and take the next dose on the regular day. Do not take two doses within 3 days of each other. The 5 day half-life means a dose 4 days late still lands while the previous one is substantially present, so the blood level dips but does not collapse.

Changing the injection day is allowed as long as the gap between doses is at least 3 days. People who miss two or more consecutive weeks are in a different situation: after about 4 weeks the drug is largely cleared, and restarting at the previous maintenance dose means the nausea of a fresh start at a high dose. The label does not spell out a restart protocol; in practice people and clinicians often drop back a step or two.

Zepbound pens and single-dose vials are fixed: each contains one labeled dose. Compounded tirzepatide from a pharmacy is a multi-dose vial at a concentration the pharmacy chose, and the dose is written as a volume or units on the prescription. Grey-market tirzepatide is a powder you reconstitute yourself. Three products, three ways of expressing the same 2.5 mg, and people move between them.

The common failure is a prescription written as units for one concentration and a refill or a new vendor at another. A 10 unit instruction means 2 mg at 20 mg/mL and 0.5 mg at 5 mg/mL. Pharmacies label the concentration on the vial, so the fix is to recompute from the label each time rather than carrying a units number from vial to vial. The FDA has published warnings about dosing errors with compounded GLP-1 vials for exactly this reason.

Regulation is also shifting. In April 2026 the FDA proposed removing tirzepatide, semaglutide and liraglutide from the 503B bulks list, which would stop outsourcing facilities compounding them from bulk powder outside a shortage. The comment period closed in June 2026 and, as of October 2026, no final decision has been reported. Our buying guide tracks where that leaves compounded supply.

Side effects follow the staircase. At 2.5 mg most people notice lower appetite, early fullness and some nausea, and a few pounds may come off. Each step up brings a flare of nausea, burping, reflux and either constipation or diarrhea for a week or two as the gut adjusts. Fatigue during the first weeks of each step is common and mostly reflects eating less. By month 3 to 6 at a stable dose the GI effects usually settle.

Higher steps carry the same effects more often. In the trials, discontinuation for adverse events rose with dose, which is part of why the label makes every increase conditional on tolerance. Hair shedding tends to appear a few months into rapid loss at any dose and tracks the rate of loss rather than the mg. Gallstones and lean mass loss are also rate-of-loss effects; see muscle loss on GLP-1 drugs.

Some effects are stop signals at any step: severe or persistent abdominal pain, especially radiating to the back, which can mean pancreatitis; pain under the right ribs with fever or yellowing, which can mean gallbladder disease; vomiting that prevents keeping fluids down; or a neck lump, hoarseness or trouble swallowing. The GLP-1 side effects article goes through each by step, including the January 2026 MHRA alert on pancreatitis.