This question usually comes up for one of two reasons. You may have taken tirzepatide before and be moving to a new provider, or you may be completely new to Mounjaro and wondering whether you can begin with 5mg instead of the lower starting strength.
If you are new to Mounjaro, the licensed starting dose is 2.5mg once weekly for the first four weeks. Starting at 5mg is not the standard licensed starting schedule. If you have already been taking tirzepatide, however, the situation can be different. Someone moving between providers while already taking 5mg may be continuing an existing treatment rather than starting from the beginning. The appropriate dose depends on your treatment history and an individual clinical assessment.
These are different situations, so it is helpful to look at them separately. This guide explains how Mounjaro dosing works, why treatment starts at a lower strength, when 5mg may be considered, what to discuss with your prescriber, and the common questions people have when starting or changing providers.
The Short Answer
The licensed starting dose of Mounjaro is 2.5mg once weekly for the first four weeks. This is the first step in the standard Mounjaro dosing schedule. After four weeks, the dose may be increased to 5mg once weekly if your prescriber considers this appropriate. The available strengths then include 7.5mg, 10mg, 12.5mg and 15mg.
If you are new to tirzepatide, 2.5mg is the licensed starting dose. You should not choose to start at 5mg yourself. Your prescriber will consider your medical history and whether Mounjaro is suitable for you before prescribing.
If you have already taken tirzepatide, you may not be starting treatment from the beginning. For example, if you are moving from another provider while already taking 5mg, your prescriber can review what you have been taking, for how long, and how you have responded to treatment. The appropriate dose can then be decided as part of your clinical assessment.
So, rather than asking only, "Can I start at 5mg?", it is more useful to ask, "Am I starting treatment, or am I continuing treatment I have already been taking?"
Why the First Four Weeks and Starting Dose Matter
The lower starting dose is there to help your body adjust to tirzepatide.
Mounjaro can cause gastrointestinal side effects, including nausea, vomiting, diarrhoea, constipation, indigestion and reduced appetite. These effects can be more noticeable when treatment is started or when the dose is increased. Starting at 2.5mg and following the recommended dosing schedule gives your prescriber an opportunity to assess how you tolerate treatment before considering an increase.
Some people find that gastrointestinal side effects improve as their body adjusts, although this varies from person to person. If you experience troublesome or persistent side effects, speak to your prescriber before increasing your dose.
It is also important not to assume that starting at a higher dose will lead to faster weight loss. The clinical studies used to assess tirzepatide looked at treatment over much longer periods, including 72 weeks. The first four weeks at 2.5mg are part of the licensed dosing schedule and give your prescriber time to assess how you are responding before deciding whether a higher dose is appropriate.
Which Situation Are You In?
| Your situation | Is this "starting at 5mg"? |
|---|---|
| Never taken tirzepatide | Yes. The licensed starting dose applies |
| Currently on 5mg with another provider | No. You are continuing, and 5mg may be appropriate |
| Was on 5mg, stopped recently | Possibly not. Depends how long the gap was |
| Was on tirzepatide a long time ago | Often treated as starting again. Your prescriber decides |
| On a different GLP-1, switching to tirzepatide | This is a switch, not a continuation. It is assessed on its own terms |
| Have a 5mg pen already and want it prescribed | The pen you have does not determine what is appropriate |
If you are transferring from another provider
This is one situation where 5mg may be appropriate without starting with a 2.5mg pen. If you are moving to a new provider, give the prescriber as much detail as possible about your current treatment.
Tell them the strength you have been taking, how long you have been taking it, when you had your last injection, and how you have tolerated the dose. If possible, also provide details of your previous prescriber or pharmacy. This information helps the prescriber decide whether continuing at 5mg or another strength is appropriate.
Try to be specific rather than simply saying that you have "been on it for a while". Clear information about your treatment history can make the assessment easier and may reduce the need for follow up questions.
If you stopped and want to restart
The length of the break matters. Your prescriber will want to know how long you have been off Mounjaro, which dose you were taking and why you stopped.
A short interruption may be managed differently from a longer break, particularly if you stopped because of side effects. Your prescriber may consider whether restarting at the same dose or a lower dose is appropriate based on your treatment history and how well you previously tolerated it.
Be open about the length of the gap and any problems you experienced. This gives your healthcare professional the information they need to make a safer decision about restarting treatment.
If you are new to tirzepatide
If you have never taken tirzepatide before, you are starting treatment. In that case, the licensed starting dose is 2.5mg once weekly for the first four weeks.
You may come across different approaches from different providers, but the standard licensed dosing schedule starts at 2.5mg. You should not choose 5mg simply because you would prefer to start at a higher strength. Your prescriber will decide the appropriate dose based on your medical history and individual circumstances.
What Not to Shop For
If another provider has declined to prescribe Mounjaro, it can be tempting to keep looking until you find one that will approve the higher dose you want.
It is worth taking a step back first. A prescribing decision should be based on your clinical assessment, not simply on the strength you request. The purpose of the assessment is to check whether treatment and the proposed dose are appropriate for you.
If you think you were declined because the provider did not have all the relevant information, provide the missing details and ask whether the decision can be reviewed. That is more useful than looking for a service with fewer checks.
If treatment or a particular strength is not considered appropriate, we may decline the request. You are not charged for medicine that is not supplied.
What Happens If You Start Higher Than the Recommended Mounjaro Dosing Schedule Anyway
Starting at a higher dose than the recommended schedule may increase the chance of experiencing side effects, particularly gastrointestinal effects such as nausea, vomiting, diarrhoea and constipation.
If you have started at a higher dose and are experiencing troublesome symptoms, speak to your prescriber rather than trying to adjust the dose yourself. Some side effects may improve as your body adjusts, but persistent or severe symptoms should be assessed by a healthcare professional.
Contact your prescriber, your GP or NHS 111 if you develop severe or persistent abdominal pain, particularly pain that spreads to the back, persistent vomiting, signs of dehydration, symptoms of low blood sugar, signs of gallbladder problems, or symptoms of a serious allergic reaction. In an emergency, call 999. Suspected side effects can also be reported through the MHRA Yellow Card scheme.
Mounjaro can also cause injection site reactions, such as a rash or swelling.
Do not try to adjust your dose by splitting doses, changing the injection interval or combining pens. If you are unsure about your prescribed strength, speak to your prescriber or pharmacy team.
What to Tell Your Prescriber
- Whether you have taken tirzepatide before and which strength you used
- Your current Mounjaro dose or the last strength you took
- How long you were taking it and when you had your last injection
- How you tolerated the treatment, including any side effects that caused you to stop
- Whether you have used another GLP 1 medicine and how you responded to it
- Any other medicines you take and any relevant medical conditions
- Your starting weight and, if relevant, your weight management goals
- If you are requesting a particular strength, explain why you are asking for it
For example, saying "I have been taking 5mg since March with another pharmacy" gives a prescriber useful information to assess your treatment history. Simply saying "I would like to start on 5mg" does not provide enough context to decide whether that dose is appropriate for you.
What It Costs
Pricing for 5mg, including bundles and current discounts, is on our Mounjaro 5mg page, and live rates are always on the Mounjaro treatment page.
One point worth noting is that cost alone should not determine the starting strength prescribed. A 2.5mg pen is the cheapest in the range, so beginning where the licence says does not cost you more over a course of treatment. If anything it costs less.
General Eligibility
Mounjaro (tirzepatide) is licensed for adults with type 2 diabetes and for weight management in eligible patients. For weight management, the licensed criteria include a BMI of 30 kg/m² or above, or 27 kg/m² or above where a weight related condition is present, such as high blood pressure, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes.
Mounjaro may not be suitable if you are pregnant, breastfeeding or trying to conceive. It may also not be appropriate if you have a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, have had pancreatitis, have certain digestive conditions, or are under 18. Your prescriber will assess your individual circumstances before deciding whether treatment is suitable.
MHRA advice issued in June 2025 recommends using additional or non oral contraception for four weeks after starting tirzepatide and for four weeks after each increase in strength. NHS eligibility criteria may differ from the licensed indication and can vary depending on local commissioning arrangements and national guidance.
Treatment suitability and the strength prescribed depend on an individual clinical assessment. The maximum licensed dose of Mounjaro is 15 mg once weekly. Our guide to prescription weight loss treatments covers the options more broadly.
Key Takeaways
- The licensed starting dose is 2.5mg once weekly for the first four weeks before moving through the dosage schedule, if appropriate
- If you are new to tirzepatide, the starting dose applies to you
- If you are transferring from another provider or restarting treatment, you may be continuing treatment rather than starting again
- Following the recommended schedule allows your prescriber to adjust your dose based on how you respond and tolerate treatment
- Starting at a higher dose does not mean you will get faster results, and it may increase the risk of side effects
- Give your prescriber your actual treatment history, including previous strengths, dates and side effects, so they can assess which dose is appropriate
- A particular strength should be prescribed based on your clinical assessment, rather than simply requested or selected when ordering
