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How long does it take for Mounjaro to start working?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Feb 22, 2023.

Official answer


Mounjaro (generic name: tirzepatide) will start to lower your blood sugar levels right away but it can take 8 to 12 weeks to reach your target A1C goal. When compared to some other diabetes treatments, studies have shown that it can take 8 weeks to reach an A1C target of ≤7% and 12 weeks to reach an A1C ≤6.5% with Mounjaro. Significant weight loss can occur as early as 28-weeks.

A1C is a simple blood test that shows the average amount of sugar (glucose) in your blood over the past 2 to 3 months. Your healthcare provider will tell you what your what A1C goal should be.

How is Mounjaro used?

Mounjaro is given as a weekly injection under the skin (subcutaneous). It is used to help lower blood glucose (sugar) levels in type 2 diabetes, alongside diet and exercise, as prescribed by your doctor. In addition to blood sugar control, Mounjaro can help you lose weight, although it is not specifically approved for this use.

The recommended starting dosage is 2.5 mg subcutaneously once weekly, increasing to 5 mg once weekly after 4 weeks. The maximum dosage is 15 mg subcutaneously once weekly. Your doctor will slowly increase your dose to help prevent sides and monitor how well it's working.

Mounjaro is available as a 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg subcutaneous injection in a single-dose auto-injector pen. You can learn to give this injection at home.

Studies for Mounjaro

In an exploratory analysis from the SURPASS-2 and SURPASS-3 studies, researchers evaluated the median time to reach certain blood sugar (glycemic) targets (the median time to A1C ≤7% and ≤6.5%). Studies also evaluated the time to reach a 5% weight loss goal among patients treated with Mounjaro or semaglutide injection (brand name: Ozempic) 1 mg.

Patients received either Mounjaro 5 mg, 10 mg or 15 mg injection; semaglutide 1 mg injection; or titrated insulin degludec (brand name: Tresiba). Of note, the 15 mg once per week injection is the maximum dose for Mounjaro.

Results showed that those taking any dose of Mounjaro reached these A1C targets about 4 weeks sooner than those using injected semaglutide (Ozempic) 1 mg. When compared to titrated insulin degludec (Tresiba), participants using Mounjaro achieved the A1C goals between 4 and 12 weeks sooner. Specifically,

  • The median time to reach A1C ≤7% was 8 weeks with Mounjaro, and 12 weeks for both semaglutide and insulin degludec.
  • The median time to reach A1C ≤6.5% was 12 weeks with Mounjaro, 16 weeks with semaglutide and 24 weeks for insulin degludec.
  • The median time to reach at least a 5% weight loss was 16 weeks with Mounjaro 5 mg, 12 weeks with Mounjaro 10 and 15 mg, and 24 weeks with injectable semaglutide 1 mg.

How fast can I lose weight with Mounjaro?

While not approved for weight loss, weight loss in adults reached 11.4 kg (25 lbs) over 40 and 52-week long Mounjaro Phase 3 studies submitted for approval to the FDA. Higher doses of Mounjaro led to greater weight loss, but can be associated with more frequent stomach side effects, like nausea, diarrhea and decreased appetite. These side effects tend to be temporary in most patients.

  • In Phase 3 studies, more patients receiving Mounjaro 5 mg (3%), 10 mg (5.4%), and 15 mg (6.6%) discontinued treatment due to gastrointestinal (digestive tract) side effects than patients receiving placebo (0.4%).
  • Most reports of nausea, vomiting, and/or diarrhea occurred when doses were being increased at the beginning of treatment and decreased over time.

Additional smaller Phase 1 studies from the SURPASS program have shown significant weight loss can occur as early as 28-weeks. At 28 weeks, participants taking Mounjaro (45 subjects) had significantly greater reductions in weight and fat mass compared to those taking injectable semaglutide (Ozempic) 1 mg (44 subjects) and placebo (28 subjects).

  • Patients taking Mounjaro 15 mg (the maximum dose) lost 11.2 kg (24.7 lb), patients taking injectable semaglutide 1 mg (Ozempic) lost 6.9 kg (15.2 lb) and those on placebo lost no weight at 28-weeks.
  • A fat loss (fat mass reduction) of 9.7 kg (21.4 lb) occurred with Mounjaro 15 mg compared to a loss of 5.9 kg (13 lb) with injectable semaglutide 1 mg.
  • Treatment with Mounjaro 15 mg injection and semaglutide 1 mg injection also led to reductions in appetite and kilocalories (kcals) consumed, but there was no difference between the two treatments for these outcomes.

This is not all the information you need to know about Mounjaro (tirzepatide) for safe and effective use and does not take the place of your doctor’s directions. Review the full Mounjaro information and discuss this information and any questions you have with your doctor or other health care provider.


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