Tirzepatide Dosage Chart: Titration Schedule, Units per Dose, Microdosing

Key takeaways

• The Zepbound label schedule: 2.5 mg once a week for 4 weeks, then 5 mg, then increases of 2.5 mg at intervals of at least 4 weeks to 7.5, 10, 12.5 and 15 mg. Maintenance doses are 5, 10 or 15 mg; 15 mg is the maximum; 2.5 mg is a starting dose, not a maintenance dose.
• Missed dose: take it within 4 days (96 hours), otherwise skip it. Never take two doses within 3 days (72 hours).
• With a compounded vial, units = dose in mg ÷ concentration in mg per mL × 100: 5 mg is 50 units from a 10 mg per mL vial, 100 units from a 5 mg per mL vial and 25 units from a 20 mg per mL vial. Only the concentration on your own label counts.
• "Microdosing" below 2.5 mg has no phase 3 data; the only trial of a lower dose (1 mg, phase 2, type 2 diabetes) produced about 0.9 kg of weight loss in 26 weeks.
• These are label and trial doses, not a recommendation. Your prescription overrides this page.

The tirzepatide dosage chart on the Zepbound label is short: start at 2.5 mg once a week for four weeks, increase to 5 mg, then raise the dose by 2.5 mg no more often than every four weeks until you reach a maintenance dose of 5, 10 or 15 mg, with 15 mg the maximum (Zepbound label). The schedule is the same whether the drug comes from a pen or from a compounded tirzepatide vial, and the side effects that pace the increases are covered in is tirzepatide safe. What changes with a vial is that every dose has to be converted into syringe units, which is the second table on this page.

The label titration schedule

"At least four weeks" is a floor, not a schedule: the label tells prescribers to weigh response and tolerability when choosing a maintenance dose, and to consider a lower one if a dose is not tolerated. In SURMOUNT-1 the escalation period ran up to 20 weeks, after which participants stayed on a fixed 5, 10 or 15 mg for the rest of the 72 weeks and lost a mean of 15.0, 19.5 and 20.9 percent of body weight, against 3.1 percent on placebo (Jastreboff 2022). Injections go under the skin of the abdomen, thigh or upper arm at any time of day, rotating sites; see the injection guide.

Maintenance doses and the maximum

Three details on the label are routinely misread.

• Maintenance doses are 5, 10 and 15 mg. 7.5 and 12.5 mg are steps on the way up; the label does not list them as maintenance doses, although a prescriber may hold someone there for tolerability.
• For obstructive sleep apnea the maintenance doses are 10 or 15 mg. The lower doses were not studied for that indication.
• There is no "maintenance dose after goal weight." The indication is to reduce weight and maintain the reduction on the same dose. The one trial of life after goal, SURMOUNT-4, kept people on 10 or 15 mg: those who continued lost a further 5.5 percent over the next year, those switched to placebo regained 14.0 percent, and only 16.6 percent of the placebo group kept at least 80 percent of their loss (Aronne 2024). Whether a lower dose or a longer interval can hold weight is untested.

Missed doses and changing your injection day

From the label: if a dose is missed, take it as soon as possible within four days (96 hours). If more than four days have passed, skip it and take the next dose on the regular day. Never take two doses within three days (72 hours) of each other. The weekly injection day can be changed as long as at least 72 hours separate the last dose and the new one (Zepbound label). Doubling up after a missed week is the most common self-inflicted overdose and is never correct.

Units per dose for compounded vials

A pen delivers a fixed dose. A compounded vial delivers whatever volume you draw, and the drug in that volume depends on the concentration the pharmacy chose and printed on the label. Insulin syringes are marked in units, and on a standard U-100 syringe 100 units equal 1 mL (see how many units are in 1 mL). So:

units = dose in mg ÷ concentration in mg per mL × 100

For 5 mg from a 10 mg per mL vial: 5 ÷ 10 = 0.5 mL, and 0.5 × 100 = 50 units. From a 5 mg per mL vial it is 1 mL = 100 units, a full 1 mL syringe. From a 20 mg per mL vial it is 0.25 mL = 25 units.

The three concentrations are examples; pharmacies use others. Use the number on your own label, and run it through the peptide calculator before the first dose from every new vial. Three things follow from the table. The same units mean different doses: 50 units is 2.5 mg from one vial and 5 mg from the next, so a pharmacy that changes concentration between refills changes your units. Half units (12.5, 37.5, 62.5) need a syringe with half-unit marks. And a 5 mg per mL vial cannot deliver 7.5 mg or more in one standard syringe, which is why higher-dose vials are more concentrated; Zepbound's own multi-dose vials run from 4.17 to 25 mg per mL so that every dose is 0.6 mL (Zepbound label).

The reason for care is documented: FDA's July 2024 alert on compounded injectable semaglutide described patients who drew 5 to 20 times their intended dose from multi-dose vials, clinicians who miscalculated by 5 to 10 times, and hospitalizations, with confusion between mL, mg and units named as a cause (FDA dosing-error alert 2024). The arithmetic for tirzepatide is the same.

What "microdosing" claims rest on

"Microdosing tirzepatide" usually means starting below 2.5 mg, staying at or below 2.5 mg as a maintenance dose, or stretching the interval past a week. It is sold as a way to avoid side effects, to make an expensive vial last, or to hold weight after goal. What the evidence says:

• No phase 3 trial has tested a dose below 2.5 mg. The SURMOUNT and SURPASS programs studied 5, 10 and 15 mg, with 2.5 mg only as a four-week starting step, and the label states that 2.5 mg is not approved as a maintenance dose (Zepbound label).
• The one lower dose ever trialed did little. In the 26-week phase 2 trial in type 2 diabetes, 1 mg weekly lowered HbA1c by 1.06 points (placebo 0.06) and weight by about 0.9 kg, against 11.3 kg at 15 mg, and 23 percent of the 1 mg group still had gastrointestinal events, against 10 percent on placebo (Frias 2018).
• The dose-response is steep at the bottom and flat at the top. In SURMOUNT-1, 5 mg delivered about three-quarters of the 15 mg effect and 10 mg nearly all of it (Jastreboff 2022); where between 0 and 5 mg the effect appears in people without diabetes, nobody has measured.
• The label already has a low-dose option. Slower escalation and a 5 mg maintenance dose are on-label answers to side effects. A 2026 clinical commentary describes microdosing as driven by gastrointestinal tolerability, cost and "vanity weight," and links it to dosing errors, pen manipulation and shared vials (Trainer 2026).

The honest statement is not that microdosing cannot work but that nobody knows, and the one data point says the effect is small. Paying for a compounded vial to take 1 mg is paying for an untested dose of an untested product.

Switching from semaglutide to tirzepatide

There is no conversion chart. The Zepbound label has no switching schedule, no equivalence between semaglutide and tirzepatide doses, and says tirzepatide should not be used with any GLP-1 receptor agonist (Zepbound label). The trials compared the drugs without matching doses: in SURPASS-2, tirzepatide 5, 10 and 15 mg all beat semaglutide 1 mg on HbA1c and weight in type 2 diabetes (Frías 2021), and in SURMOUNT-5 maximum tolerated tirzepatide (10 or 15 mg) produced 20.2 percent weight loss against 13.7 percent for maximum tolerated semaglutide (1.7 or 2.4 mg) in obesity (Aronne 2025). That says tirzepatide did more at every dose tested, not which tirzepatide dose equals yours. The only schedule on the label starts at 2.5 mg; where a clinician starts someone coming off semaglutide is a judgment the trials do not settle.

Bottom line

The chart is four weeks at 2.5 mg, then 5 mg, then 2.5 mg steps at least four weeks apart to a maintenance dose of 5, 10 or 15 mg; miss a dose and you have four days to take it. The hard part is not the schedule but the vial: a dose in mg becomes a volume in units only through the concentration on your label, and that conversion is where the documented overdoses happened. Below 2.5 mg there is one small trial and a lot of marketing.

Frequently asked questions

+−What is the starting dose of tirzepatide?

2.5 mg injected under the skin once a week for four weeks, for every indication on the Zepbound label. After four weeks the dose rises to 5 mg. The 2.5 mg dose exists to let the gut adjust and is not approved as a maintenance dose; the same start applies to compounded tirzepatide, where 2.5 mg is 25 units from a 10 mg per mL vial.

+−What is the highest dose of tirzepatide?

15 mg once a week is the maximum on the label for all indications. The step above 12.5 mg is reached no sooner than week 21 if every increase is made at the minimum four-week interval. In SURMOUNT-1, 15 mg produced a mean weight loss of 20.9% at 72 weeks, against 19.5% at 10 mg, so the last step adds comparatively little for most people.

+−What is a maintenance dose of tirzepatide?

The label names 5, 10 and 15 mg as maintenance doses for weight management and 10 or 15 mg for obstructive sleep apnea; 7.5 and 12.5 mg are escalation steps. If a maintenance dose is not tolerated, the label says to consider a lower one. The only trial of what happens after reaching goal, SURMOUNT-4, kept people on their 10 or 15 mg dose; those switched to placebo regained 14% of body weight within a year.

+−How many units is 2.5 mg of tirzepatide?

It depends entirely on the concentration printed on your vial. On a U-100 insulin syringe, 2.5 mg is 50 units from a 5 mg per mL vial, 25 units from a 10 mg per mL vial and 12.5 units from a 20 mg per mL vial. The formula is dose in mg divided by concentration in mg per mL, times 100. Units measure volume, not drug, so never carry a units number from one vial to the next without redoing the arithmetic.

+−What is microdosing tirzepatide?

Taking less than the label's 2.5 mg starting dose, or stretching the interval beyond a week, usually to limit side effects, cut cost or hold a weight after reaching goal. No phase 3 trial has tested a dose below 2.5 mg. The only lower dose ever studied, 1 mg weekly in a 26-week phase 2 trial in type 2 diabetes, lowered HbA1c by about one point and weight by under a kilogram, with gastrointestinal side effects in 23% of participants. The label already allows a slower climb and a 5 mg maintenance dose for people who struggle with side effects.

+−What happens if I miss a dose of tirzepatide?

Take it as soon as you can within four days (96 hours) of the missed dose, then continue on your usual day. If more than four days have passed, skip it and take the next dose on schedule. Never take two doses within three days (72 hours) of each other. You can also move your injection day permanently, as long as at least 72 hours separate the two doses.

+−Can you switch from semaglutide to tirzepatide, and at what dose?

The Zepbound label has no switching schedule and no dose-equivalence table, and it says tirzepatide should not be taken together with any GLP-1 drug. The trials compared tirzepatide 5, 10 and 15 mg with semaglutide 1 mg in type 2 diabetes and maximum doses of each in obesity, which tells you tirzepatide produced more weight loss at every dose tested, not which tirzepatide dose matches your semaglutide dose. The only schedule on the label starts at 2.5 mg; where to start after semaglutide is a clinician's decision.

Sources

1. LabelEli Lilly. Zepbound (tirzepatide) injection, for subcutaneous use: prescribing information, revised August 2026 (DailyMed). (2026)
2. StudyJastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205-16. (2022)
3. StudyFrias JP et al. Efficacy and safety of LY3298176, a novel dual GIP and GLP-1 receptor agonist, in patients with type 2 diabetes: a randomised, placebo-controlled and active comparator-controlled phase 2 trial. Lancet 2018;392:2180-93. (2018)
4. StudyAronne LJ et al. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity: the SURMOUNT-4 randomized clinical trial. JAMA 2024;331:38-48. (2024)
5. StudyAronne LJ et al. Tirzepatide as compared with semaglutide for the treatment of obesity (SURMOUNT-5). N Engl J Med 2025;393:26-36. (2025)
6. StudyFrías JP et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med 2021;385:503-15. (2021)
7. ReviewTrainer N. The 'microdosing' dilemma: balancing patient anecdotes with clinical safety amid GLP-1 compounding restrictions. J Am Assoc Nurse Pract 2026, online May 26. (2026)
8. RegulatoryFDA. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. July 26, 2024. (2024)