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How Long Do You Take Mounjaro For Weight Loss?

Mounjaro for weight loss is a UK-approved injectable medicine containing the active ingredient tirzepatide.

It is a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. Mounjaro works by mimicking these two hormones, GIP and GLP-1, that are secreted during digestion when sugary foods are consumed, stimulating insulin release.

How long you need to take Mounjaro for weight loss will depend on how your body tolerates and responds to tirzepatide.

Here we’ll explore the Mounjaro dosage regimen, how long it takes to work, and what happens when you stop using it.

Mounjaro dosage

Mounjaro injection doses are titrated to help reduce the likelihood of side effects. The starting dose is 2.5 mg and the maximum dose is 15 mg. To reach the maximum maintenance dose, it should take 6 months. However, the exact duration varies from person to person.

The following table details the typical Mounjaro dosage regimen:

2.5 mg1 to 4
5 mg5 to 8
7.5 mg9 to 12
10 mg13 to 16
12.5 mg17 to 20
15 mg21 to 24

Although it will take 6 months to reach the maximum maintenance dose of 15 mg, some people may not need the full dose. The 5 mg and 10 mg doses are also maintenance doses and your clinician will advise which dose you will need.

The higher doses of Mounjaro will provide the biggest benefits but are also more likely to cause side effects. If you experience side effects, your clinician may advise that you remain on your current dose or could reduce your dose further.

How often do you inject Mounjaro for weight loss?

Mounjaro weight loss injections are injected into your skin once per week.

When you are first prescribed Mounjaro, decide which day of the week is most convenient for you. You should then inject the Mounjaro pen on the same day each week. You should use the weight loss injection at the same time, too.

For example, if you inject your first dose on a Monday at 10 am, it’s advisable to inject your next dose at 10 am on the following Monday and so on.


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  • Approved Weight Loss Treatment
  • Suitable for adults with a BMI of +30kg/m²
  • Pre-filled injection pen

How long does Mounjaro take to start working?

Mounjaro starts working as soon as you inject the first dose. However, it may take 4 weeks to see any noticeable results.

A randomised controlled trial showed that participants assigned to tirzepatide treatment (5 mg, 10 mg or 15 mg) had all started to lose weight within the first 4 weeks. The results showed that at 4 weeks the average weight loss was 2 kg and at 8 weeks this had doubled to 4 kg for all doses.

How long do you take Mounjaro for weight loss?

Mounjaro (tirzepatide) is safe for long-term use and should be used until you have reached your weight loss targets or your clinician tells you to stop. Some studies have investigated the safety of Mounjaro’s active ingredient over 18 to 24 months.

The SURMOUNT-2 trial assessed the safety and effectiveness of tirzepatide for weight loss in obese people with type 2 diabetes. The study took place over 72 weeks and demonstrated that a once-weekly 10 mg or 15 mg tirzepatide dose resulted in significant weight loss, and had a similar safety profile to other weight loss therapies.

The SURMOUNT-4 randomised clinical trial investigated the efficacy of once-weekly tirzepatide weight loss injections for 88 weeks compared to a placebo. The results found that continued tirzepatide use resulted in an average weight reduction of 25.3% compared to 9.9% for a placebo.

A systematic review published in 2023 involving 9 randomised clinical trials found that the overall safety profile of tirzepatide is similar to other GLP-1 receptor agonists, like Wegovy, but higher doses could cause gastrointestinal side effects.

Overall, how long you’ll need to use Mounjaro for weight loss depends on your situation and how much weight you want to lose. Mounjaro is most effective when you follow a personalised weight loss strategy. A qualified medical professional can work with you to devise a suitable diet and exercise plan. If you have not lost 5% of your body weight within 6 months of using Mounjaro, your clinician will reassess its benefits for you and may discuss other weight loss alternatives.

What happens when you stop taking Mounjaro?

Recent research shows that people who stop using Mounjaro for weight loss regain a substantial percentage of the weight they have lost while receiving treatment. The Surmount-4 study involved 783 participants receiving either a 10 or 15 mg weekly dose of tirzepatide for 36 weeks, before being randomised to either continue taking tirzepatide or switch to a placebo.

The results showed that those receiving the continued tirzepatide treatment maintained at least 80% of the weight loss they had achieved in the 36-week lead-in period. However, of those who received a placebo from 36 weeks, 9.9% maintained significant weight loss but improvements in cardiometabolic risk factors were reversed. While others regained 14% of their body weight, suggesting that stopping treatment increases the chances of putting weight back on.

Why do you regain weight when you stop Mounjaro?

Several factors contribute to weight gain when you stop using Mounjaro for weight loss. Mounjaro works by imitating 2 important digestive hormones, GIP and GLP-1, causing:

  • Enhanced insulin secretion
  • Improved insulin sensitivity
  • Reduced appetite and food intake

When you stop Mounjaro for weight loss, your appetite will likely return, increasing your calorie intake and weight gain.

Mounjaro is also most effective when it is used alongside a diet and exercise plan. If you haven’t changed your diet or introduced regular exercise into your daily routine while using Mounjaro, then weight gain is more likely when you stop it. That’s because poor diets consisting of processed foods, and high fat and sugar intakes are associated with obesity. Sedentary lifestyles are also a contributing factor to weight gain.


How long you’ll need to use Mounjaro weight loss injections depends on your circumstances and how well your body responds to treatment. It can take 6 months to reach the maximum maintenance dose, although some people will respond to a lower dose.

Your clinician will advise you of the most suitable dose for you and the duration of your treatment with Mounjaro.


Authored By

Leanne Edermaniger

Medical Content Writer
Leanne is a science and health content writer focusing on human health and biology while utilising her solid academic background.

Published on: 21/05/2024

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist
Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 21/05/2024
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