Second Nature logo



How quickly do you lose weight on Mounjaro?

Robbie Puddick
Written by

Robbie Puddick

Medically reviewed by

Fiona Moncrieff

5 min read
Last updated December 2023

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.

Check your eligibility for our Wegovy-supported programme.

Is Mounjaro available in the UK?

Mounjaro has been approved for weight loss and type 2 diabetes in the UK and will be available by early 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.

Can I buy Mounjaro in the UK?

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

However, as Mounjaro’s only just been approved, it’s unclear when the supply chains for the medication will open up.

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, you’ll only need to pay the base fee for a prescription of £9.95.

Via private prescription, the cost of Mounjaro isn’t known in the UK, as it’s only been approved as of November 2023.

The current retail cost for Mounjaro in the U.S. is around $1500 (£1231) a month. However, medication costs are much lower in the UK, and likely Mounjaro will cost between £200-£350 a 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.

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 trusted 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.

So, if you’ve decided you want to try a weight-loss jab with the support of the Second Nature programme, click on the button below.

Check your eligibility for our Wegovy-supported programme.

You might also like

Make losing weight feel Second Nature

The first step on your Second Nature journey is to take our health quiz.

Hand holding phone

Write a response

As seen on

The GuardianThe TimesChannel 4The Sunday Telegraph
Evening Standard