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How quickly do you lose weight on Mounjaro?

Robbie Puddick
Written by

Robbie Puddick

Medically reviewed by

Fiona Moncrieff

5 min read
Last updated February 2024

Jump to: Is Mounjaro available in the UK? | Is Mounjaro available on the NHS? | Can I buy Mounjaro in the UK? | Can I get Mounjaro over the counter? | How much does Mounjaro cost in the UK? | Which is better, Ozempic or Mounjaro? | Which is better, Wegovy or Mounjaro? | What’s the difference between Wegovy and Mounjaro? | Does Mounjaro have side effects?

According to randomised controlled trials, you start losing weight immediately after taking Mounjaro. After four weeks, the average weight loss is around 2% of body weight; after eight weeks, it’s over 4%.

Mounjaro (tirzepatide) reduces appetite and hunger, helping you eat fewer calories; this effect is almost immediate.

However, you might notice the impact of lower hunger wearing off after 4-5 days post-injection in the first month of taking Mounjaro.

It can take around four weeks for Mounjaro to reach a level in the body we call a steady state. A steady state is when the drug’s levels in the body remain consistent rather than spiking and falling.

Interestingly, this initial weight loss is no different to other weight loss treatments or the impact of diet interventions on weight loss. The real effect of tirzepatide is seen beyond three months.

Tirzepatide is a long-acting medication that’s started at a lower dose to reduce the number and severity of side effects as it’s built up to a higher maintenance dose.

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Is Mounjaro available in the UK?

Mounjaro has been approved for weight loss and type 2 diabetes in the UK and will be available to purchased privately in Feb 2024. It was approved for type 2 diabetes in September 2023 and weight loss in November 2023.

However, it can take some time after approval for these medications to become available through pharmacies and the NHS.

Is Mounjaro available on the NHS?

You can’t get Mounjaro on the NHS yet, and it’s unclear when it will be prescribed through the NHS.

It may only be available as a private prescription before becoming more widely available on the NHS through specialist weight management services.

However, Mounjaro’s approval has only just been announced (as of November 2023), so it’s unclear what approach the NHS will take on providing Mounjaro to patients.

Second Nature's Mounjaro Weight Loss Programme: Join our waiting list

Can I buy Mounjaro in the UK?

You can buy Mounjaro from pharmacies, approved online retailers, and specialist weight-loss programmes in the UK.

Second Nature is launching its Mounjaro weight-loss programme in Feb 2024.

Can I get Mounjaro over the counter?

You can’t get Mounjaro over the counter and need a prescription for the medication when it becomes available.

If you purchase Mounjaro from an online pharmacy, you must complete an online form before receiving approval for the medication.

How much does Mounjaro cost in the UK?

To purchase a prescription for Mounjaro via the NHS in England, you’ll only need to pay the base fee for a prescription of £9.95.

With Second Nature, you can purchase Mounjaro as part of our Mounjaro programme, which starts from £229 per month.

Which is better, Ozempic or Mounjaro?

Mounjaro is more effective at supporting weight loss than Ozempic. However, Ozempic is no longer available in the UK as a weight-loss jab, so the comparison is irrelevant for weight-loss treatment.

However, Ozempic and Moujaro are both approved as a treatment for people living with type 2 diabetes in the UK, and research has shown that all three doses of Mounjaro lead to more significant blood sugar reductions than Ozempic.

To read our guide comparing Ozempic to Mounjaro, click here.

Second Nature's Mounjaro Weight Loss Programme: Join our waiting list

Which is better, Wegovy or Mounjaro?

The higher doses of Mounjaro (10mg & 15mg) are more effective for weight loss and blood sugar than Wegovy, based on an indirect analysis of individual studies.

However, no studies have compared the two medications directly against one another in a double-blinded randomised controlled trial (where neither the researchers nor the participants know which medication they’ve been given).

So, Mounjaro seems more effective than Wegovy for weight loss, but we need a study comparing the two weight-loss injections to confirm this.

What’s the difference between Wegovy and Mounjaro?

When we eat food, our gut releases many hormones that help the body regulate hunger and blood sugar levels. Two of these hormones are called GLP-1 and GIP.

Wegovy mimics the hormone GLP-1 to lower hunger and manage blood sugar levels; this helps us eat fewer calories and lose weight.

Mounjaro, similar to Wegovy, also mimics the hormone GLP-1 and shares the same actions.

However, Mounjaro also mimics the hormone GIP, which helps lower appetite and manage blood sugar levels.

Therefore, whilst Wegovy mimics GLP-1, Mounjaro mimics GLP-1 and GIP and is considered a dual-action weight-loss injection and is likely more effective than Wegovy.

To read our guide comparing Wegovy to Mounjaro, click here.

Does Mounjaro have side effects?

The most common side effects of Mounjaro are nausea, constipation, vomiting, and other symptoms affecting the gastrointestinal (GI) tract, like diarrhoea.

You might also experience less common side effects like tiredness or headaches.

These symptoms most commonly occur around the time of the injection, during dose escalation, and are typically transient and will ease after you’ve adapted to the medication.

However, everyone responds differently to these medications; some people won’t experience any side effects, while others will have to discontinue their medication due to the discomfort the side effects cause.

Not a magic pill

Weight loss injections are designed as additional tools for weight management interventions and shouldn’t be considered lifelong medications.

Instead, they should be used to help you kickstart your weight loss and healthy journey while you commit to living a healthier lifestyle.

Consider the use of antidepressants for people living with depression. They’re not designed to cure the condition. Instead, they’re designed to allow room for therapy to treat the condition’s underlying cause.

Mounjaro, and other weight loss injections, like Ozempic and Wegovy, are similar. They can allow you to make lifestyle changes to support long-term weight loss maintenance.

At Second Nature, we’ve been used by the NHS since 2017 to support people with type 2 diabetes and obesity to lose weight, manage their blood sugar levels, and lead healthier lifestyles for the long term.

Ideally, we’d lose weight without medication, and we’d recommend trying our weight-loss programme before trying a weight-loss injection, as it’s cheaper and potentially more sustainable in the long term.

In 2022, the NHS published data in the BMJ that compared the weight loss outcomes of five providers in the National Diabetes Prevention Programme.

Second Nature was more than twice as effective at supporting weight loss than the other four providers.

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Write a response

Lisa Engels

18 February, 2024

I’m been using Mounjaro for 9 months
I lost 40 pounds on my own over 5 years before starting the injections
In April of 2023 I weighed 170 pounds and my a1c was around 8. I was using Lantas, Humalog, Trulicity and Jardiance
As of February 2024 I’m down to 118 pounds (high school weight), a1c is 5.1 (not even pre-diabetes)
I was up to 12.5 of Mounjaro and now on 10 maintenance dose.
I had nausea the first 2 months and surprised at how little I eat and still have energy
If you love to eat this is not a regimen for you
It’s more of a reminder to self to eat
Good luck in your journey


17 February, 2024

I started Mounjour 5 days ago. I lost 9lbs already! I immediately felt my appetite decrease, however, I also had some side affects. I felt the sensitivity when I injected, I also felt headaches and the tireness. No nausea or diarrhea. I have been drinking more water and staying hydrated. I am avoiding the sugary drinks and eating less carbs as well. I would highly recommend reading about Mounjour for the side affects and monitor how you are feeling. I am approaching my weight loss journey as a life style change and not solely relying on Mounjour to do the work alone. Look forward to my first month progress!


15 December, 2023

I just started the mounjaro. My appetite was affected immediately. I have to force myself to eat in order to take other medications. I’m not sure if I should continue this or not. I’m going to try it for 30 days & see how it works.

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