Guides / Comparing and switching

Mounjaro vs Zepbound

Same medicine, same doses, same pens and vials. The difference is what each one is approved for, and in the UK there's only Mounjaro.

By PeptideTracker editorial team · Updated November 8, 2026 · 4 sources

[00] Short answer

  1. Mounjaro and Zepbound both contain tirzepatide, which acts on the GIP and GLP-1 receptors. Both are injected once a week1–2.
  2. Both start at 2.5 mg for 4 weeks and go up in 2.5 mg steps to a maximum of 15 mg a week in adults1–2.
  3. In the US, Mounjaro is approved for type 2 diabetes. Zepbound is approved for weight reduction and for moderate to severe obstructive sleep apnea with obesity1–2.
  4. Both come as single-dose pens, single-dose vials, 4-dose vials and 4-dose KwikPens in the same six strengths1–2.
  5. In the UK, Mounjaro is licensed for both type 2 diabetes and weight management. The MHRA lists no other tirzepatide brand3–4.

What's the difference between Mounjaro and Zepbound?

The difference is the approved use, not the medicine. Mounjaro and Zepbound both contain tirzepatide, made by Eli Lilly, with the same 2.5 mg to 15 mg weekly doses1–2. In the US, Mounjaro is a type 2 diabetes medicine and Zepbound is a weight and sleep apnea medicine1–2.

Mounjaro vs Zepbound, from the US prescribing information
MounjaroZepbound
Active ingredientTirzepatide1Tirzepatide2
US approved usesBlood sugar control in type 2 diabetes in adults and children 10 and older; lowering heart attack, stroke and heart death risk in adults with type 2 diabetes at high risk1Weight reduction in adults with obesity, or overweight plus a weight-related condition; moderate to severe obstructive sleep apnea in adults with obesity2
Starting dose2.5 mg weekly12.5 mg weekly for 4 weeks2
Dose stepsUp 2.5 mg at a time after at least 4 weeks, if more blood sugar control is needed15 mg after 4 weeks, then up 2.5 mg at a time after at least 4 weeks2
Maintenance dosesNo fixed list; the label steps up only if more blood sugar control is needed15, 10 or 15 mg for weight; 10 or 15 mg for sleep apnea2
Maximum weekly dose15 mg in adults, 10 mg in children115 mg2
Missed doseWithin 4 days (96 hours), otherwise skip1Within 4 days (96 hours), otherwise skip2
Changing your injection dayAt least 3 days (72 hours) between doses1At least 3 days (72 hours) between doses2
Half-lifeAbout 5 days1About 5 to 6 days in people with obesity2
Nausea in the main label table12% to 18% on 5 to 15 mg vs 4% on placebo (diabetes trials)125% to 29% on 5 to 15 mg vs 8% on placebo (weight trials)2

The nausea figures come from different trials in different people, so they aren't directly comparable. Both labels say so.

The Zepbound label says its 2.5 mg dose "is for treatment initiation and is not approved as a maintenance dosage"2. The Mounjaro label adds each step only if more blood sugar control is needed1.

Do Mounjaro and Zepbound come in pens or vials?

Both come in pens and vials, in the same strengths. Each label lists single-dose pens and single-dose vials of 2.5, 5, 7.5, 10, 12.5 and 15 mg in 0.5 mL, plus multi-dose vials and KwikPens that each hold 4 weekly doses of 0.6 mL1–2.

Mounjaro and Zepbound presentations (US prescribing information, section 3; identical on both labels)
PresentationDosesWhat's in it
Single-dose pen12.5 to 15 mg in 0.5 mL; you don't measure anything1–2
Single-dose vial12.5 to 15 mg in 0.5 mL; you draw it up with a syringe1–2
Multi-dose vial4From 10 mg/2.4 mL (four 2.5 mg doses) to 60 mg/2.4 mL (four 15 mg doses), 0.6 mL per dose1–2
KwikPen4Same strengths as the multi-dose vial; the pen dials one fixed dose1–2
  • For vials, both labels say to use a syringe that can measure the dose, "e.g., a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose", with a new syringe and needle every time1–2.
  • Single-dose pens and vials can be kept unrefrigerated, at no more than 30°C (86°F), for a total of 21 days. Multi-dose vials and KwikPens are thrown away 30 days after first use or after 4 doses1–2.
  • Both labels say people should be trained on the specific pen or vial they get, and retrained if it changes1–2.
[Tool]Read a 1 mL syringe in mL and units0.5 mL is the 50-unit line; 0.6 mL is the 60-unit line

Is Zepbound available in the UK?

In the UK, tirzepatide is sold as Mounjaro for both type 2 diabetes and weight management. The MHRA's list of licensed GLP-1 medicines names Mounjaro as the tirzepatide brand and lists it as licensed for both uses4. Zepbound isn't on that list.

  • The UK Mounjaro SmPC covers type 2 diabetes in adults and children 10 and older, and weight management in adults with a BMI of 30 or more, or 27 to 30 with a weight-related condition3.
  • The UK schedule matches the US one: 2.5 mg for 4 weeks, then 5 mg, then 2.5 mg steps after at least 4 weeks, up to 15 mg3.
  • The UK pen is a KwikPen with 4 doses of 0.6 mL3. See Mounjaro pen doses in the UK for why the leftover liquid isn't a 5th dose.
  • For weight management, the UK SmPC says to decide whether to continue if you haven't lost at least 5% of your starting weight 6 months after reaching your highest tolerated dose3.

Can you take Mounjaro and Zepbound together?

No. The Zepbound label says using it with other tirzepatide products, or with any GLP-1 medicine, is not recommended2. Since Mounjaro is tirzepatide too, taking both would double the same medicine.

The same rules on missed doses apply to both: take a missed dose within 4 days, otherwise skip it1–2. The missed-dose guide has the day-by-day table, and the tirzepatide dosage chart has every dose in mg and mL.

Comparing tirzepatide with semaglutide? See Wegovy vs Zepbound and Ozempic vs Mounjaro.

Questions

Is Mounjaro the same as Zepbound?

Same medicine. Both are tirzepatide, with the same 2.5 mg to 15 mg weekly doses and the same pens and vials. In the US, Mounjaro is approved for type 2 diabetes and Zepbound for weight reduction and obstructive sleep apnea with obesity.

Why is Mounjaro used for weight loss in the UK?

Because the UK licence for Mounjaro covers weight management as well as type 2 diabetes. In the US those uses are split between two brand names, Mounjaro and Zepbound.

Do Zepbound vials work the same as the pens?

They contain the same medicine and doses. A single-dose vial holds one dose in 0.5 mL, which you draw up with a 1 mL syringe, using a new syringe and needle each time. A single-dose pen gives the dose without measuring.

Is 5 mg of Mounjaro the same as 5 mg of Zepbound?

Both are 5 mg of tirzepatide. The labels list the same strengths for both brands. If you change brand or presentation, your prescriber decides the dose, and the pen or vial instructions may differ.

Is Zepbound approved for type 2 diabetes?

No. Zepbound is approved for weight reduction and for moderate to severe obstructive sleep apnea in adults with obesity. Mounjaro is the tirzepatide brand approved for type 2 diabetes in the US.

Sources

Checked against Mounjaro and Zepbound US prescribing information (both revised 08/2026), the UK Mounjaro KwikPen SmPC and the MHRA's GLP-1 guidance (February 2026). How we check

  1. 1Mounjaro (tirzepatide) US prescribing information, sections 1, 2.1, 2.2, 3, 6.1, 12.3 and 16.2. Eli Lilly, revised 08/2026; Table 1
  2. 2Zepbound (tirzepatide) US prescribing information, sections 1, 2.1 to 2.4, 3, 6.1, 12.3 and 16.2. Eli Lilly, revised 08/2026; Table 1
  3. 3Mounjaro KwikPen solution for injection in pre-filled pen, UK SmPC, sections 2, 4.1 and 4.2. eMC, updated 8 Sep 2026
  4. 4MHRA: GLP-1 medicines for weight loss and diabetes: what you need to know (GOV.UK). updated 5 Feb 2026

This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.

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