In short: Switching from tirzepatide (brand name Mounjaro) to semaglutide (brand name Wegovy) is possible, but it should be planned with a prescriber. The two medicines work differently and have no validated dose equivalence, so semaglutide is usually started at its lowest weekly dose and increased gradually. The switch is normally made either on the day your next tirzepatide dose would have been due or after a short gap of about one to two weeks.

This guide, written by a Ready Health prescribing pharmacist, explains why people consider switching, how the two medicines differ, and what a safe switch usually involves.

Why do people switch from tirzepatide to semaglutide?

Common reasons include:

Side effects: some people tolerate one medicine better than the other.
Personal circumstances: changes in cost, supply or access to private treatment.
NHS access: both medicines are recommended by NICE, but through different NHS routes and for different groups of patients (see below).
Preference for a tablet: semaglutide is now also licensed in the UK as a daily tablet for weight management.

A switch is not right for everyone. Your prescriber will weigh up how well your current treatment is working, your health conditions and what you hope to achieve.

How do tirzepatide and semaglutide differ?

	Tirzepatide	Semaglutide (weekly injection)
How it works	Acts on GLP-1 and GIP receptors	Acts on GLP-1 receptors
How often	Once weekly injection	Once weekly injection (a daily tablet is also licensed)
Licensed dose range for weight management	2.5 mg up to 15 mg, increased in 2.5 mg steps every four weeks or more	0.25 mg up to 2.4 mg, increased every four weeks; a 7.2 mg dose was approved in January 2026 for adults with a BMI of 30 or more
NHS route (England)	NICE TA1026, phased rollout in primary care for prioritised groups	NICE TA875, via specialist weight management services

In the SURMOUNT-5 trial, published in 2025, adults with obesity (without type 2 diabetes) lost on average 20.2% of their body weight on tirzepatide and 13.7% on semaglutide over 72 weeks. These are averages: individual responses vary, and some people do well on either medicine.

How do you switch safely from tirzepatide to semaglutide?

Agree the timing. UK pharmacy guidance describes two common options: starting semaglutide on the day your next tirzepatide dose would have been due, or leaving a gap of about one to two weeks, which is often preferred if you have had significant side effects. Read more in our guide to washout periods when switching medication.
Start low. Even if you were on a high dose of tirzepatide, semaglutide is normally started at 0.25 mg weekly and increased step by step.
Never overlap. Do not use two GLP-1 based medicines at the same time.
Review contraception and pregnancy plans. The MHRA advises effective contraception while taking these medicines and stopping semaglutide at least two months before trying to conceive.
Keep in touch. Your prescriber should review your side effects, progress and dose increases regularly.

What side effects should I watch for after switching?

Digestive side effects such as nausea, diarrhoea, constipation and vomiting are most likely in the first few weeks and after each dose increase. Drink enough fluids, eat smaller meals and stop eating when you feel full. Seek urgent medical help for severe, persistent tummy pain, especially if it spreads to your back, as the MHRA strengthened its warning about acute pancreatitis with all GLP-1 based medicines in January 2026.

Frequently asked questions

Will I lose the same amount of weight on semaglutide?

It varies. On average, trials have shown greater weight loss with tirzepatide, but many people still achieve meaningful results with semaglutide. Your weight may plateau while the dose is being increased.

Do I have to restart at the lowest dose?

Usually, yes. Because there is no reliable dose conversion between the two, starting at 0.25 mg weekly helps reduce side effects.

Can I switch from tirzepatide injections to a semaglutide tablet?

This may be possible, but it is a different active ingredient, so a washout and a low starting dose are usually needed. Your prescriber will advise.

Is tirzepatide available on the NHS now?

Yes, for some people. NICE recommends it, and NHS England began a phased rollout in primary care in 2025, prioritising people with the highest BMI and several weight-related conditions. Eligibility is being widened in stages.

Key takeaways

Switching from tirzepatide to semaglutide should be planned with a prescriber.
Start semaglutide on the next scheduled dose day or after a short gap, as advised.
Expect to restart at 0.25 mg weekly and increase gradually.
Average weight loss tends to be lower with semaglutide, but responses vary.
Know the warning signs of pancreatitis and review your contraception.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician. Brand names are trademarks of their respective owners.

If you are considering a change to your weight-management treatment, you can book a weight-management consultation at Ready Health in Standish, Wigan. A prescriber will review your history and decide with you whether a switch is suitable.