How quickly does Mounjaro work?

When you start taking Mounjaro (tirzepatide), whether it’s for weight loss, blood sugar control, or both, it can take some time before you notice the medication’s effects. We spoke with Dr. Felix Gussone, MD about how fast Mounjaro starts to work.

On the molecular level, Mounjaro starts to work right after you take your first dose. But you likely won’t notice any effects of the medication in terms of blood sugar changes and weight loss for some time. 

If you’re prescribed Mounjaro off-label for weight loss, it can take up to a year or more to see its full effects—15–20% weight loss from your starting weight. However many people begin losing weight way earlier, typically within a few weeks of starting the injections, because they notice an immediate reduction in appetite. Others may require higher doses to see these effects. One study showed an average of 6% weight loss after 2 months. Keep in mind that the dose of the Mounjaro is gradually increased each month, so you can expect more dramatic results as your dosage is titrated by your treating physician. 

Mounjaro is FDA-approved to help people with type 2 diabetes manage their blood sugar levels. Similar to its weight loss effects, Mounjaro starts working on blood sugar levels right after the first dose. However, it can take a couple of weeks or months to reach your target hemoglobin A1C, which is a measure of how well your blood sugar levels are controlled over time.

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Current version

November 09, 2023

Written by

Felix Gussone, MD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.