Who can get weight loss injections in the UK? Learn the BMI criteria for Mounjaro and Wegovy, who should not take them, and how online eligibility checks work.
Am I eligible for weight loss injections in the UK?
In the UK, prescription weight loss injections such as Mounjaro and Wegovy are licensed for adults with a BMI of 30 or more, or a BMI of 27 or more with at least one weight-related health condition.
But BMI is only the starting point.
Eligibility also depends on:
- Your age
- Your medical history
- Any medicines you currently take
- Whether you are pregnant, breastfeeding or planning a pregnancy
- Whether you have a history of an eating disorder
- Whether treatment is clinically appropriate and safe for you
This is why weight loss injections are prescription-only medicines. A qualified prescriber must review your circumstances before treatment can be supplied.
This guide explains the BMI criteria, how to calculate your BMI, which conditions count as weight-related, who should not take these medicines, how NHS and private eligibility differ, and what to expect from an online consultation.
What are the BMI criteria for Mounjaro and Wegovy?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both licensed for weight management in adults with:
- A BMI of 30 kg/m² or above (classed as obesity), or
- A BMI of 27 kg/m² to below 30 kg/m² (classed as overweight) plus at least one weight-related health condition
Both medicines are licensed for use alongside a reduced-calorie diet and increased physical activity.
These criteria come from the licensed product information approved by the UK medicines regulator, the MHRA. Private prescribers generally use these licensed criteria when assessing whether treatment may be suitable.
What is BMI and how do you calculate it?
BMI stands for Body Mass Index. It is a measure that uses your height and weight to estimate whether your weight is in a healthy range.
The formula is:
BMI = weight (kg) ÷ height (m) ÷ height (m)
For example, someone who weighs 95 kg and is 1.70 m tall:
- 1.70 × 1.70 = 2.89
- 95 ÷ 2.89 = 32.9
That person would have a BMI of approximately 32.9.
The NHS provides a free online BMI calculator if you prefer not to work it out yourself.
For adults, BMI is usually categorised as:
- Below 18.5: underweight
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 to 39.9: obesity
- 40 or above: severe obesity
What counts as a weight-related health condition?
If your BMI is between 27 and 30, you will usually need at least one weight-related health condition to be considered for treatment.
Examples of conditions that may be relevant include:
- Prediabetes (raised blood sugar that is not yet diabetes)
- Type 2 diabetes
- High blood pressure (hypertension)
- High cholesterol or other blood lipid problems (dyslipidaemia)
- Obstructive sleep apnoea
- Cardiovascular disease, such as a previous heart attack or stroke
Other conditions associated with excess weight, such as osteoarthritis, polycystic ovary syndrome (PCOS) or fatty liver disease, may also be discussed as part of your consultation. Your prescriber will decide whether a condition is relevant to your eligibility.
You may be asked to provide evidence of a diagnosis, or for permission to contact your GP to confirm it.
Are BMI thresholds different for some ethnic groups?
Yes, this is an important point that is often overlooked.
Research shows that people from some ethnic backgrounds face a higher risk of conditions such as type 2 diabetes and heart disease at a lower BMI.
NICE guidance therefore recommends lower BMI thresholds (usually reduced by 2.5 kg/m²) for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background.
For example, in NICE guidance, a BMI of 27.5 or more in these groups is treated in a similar way to a BMI of 30 or more in the general population.
How ethnicity is taken into account can differ between the NHS and private services, and between individual prescribers. If this applies to you, mention it during your consultation so it can be considered.
Is BMI a perfect measure?
No.
BMI is a useful and widely used screening tool, but it has limitations.
BMI does not distinguish between muscle and fat. A very muscular person, such as a rugby player or bodybuilder, can have a high BMI without having excess body fat.
BMI also does not show where fat is stored. Fat stored around the waist and internal organs is more strongly linked to health risks than fat stored elsewhere.
For this reason, NICE also recommends using waist-to-height ratio alongside BMI. A waist measurement that is half your height or more suggests increased health risk.
Your prescriber will look at the whole picture, not just one number.
Who should not take weight loss injections?
Even if your BMI meets the criteria, weight loss injections are not suitable for everyone.
Treatment is generally not suitable if you:
- Are pregnant or trying to become pregnant
- Are breastfeeding
- Are under 18 (online weight-management services in the UK generally treat adults only)
- Have a current or previous eating disorder, such as anorexia, bulimia or binge eating disorder, unless under specialist supervision
- Have had an allergic reaction to the medicine or any of its ingredients
Extra caution, specialist advice or a different treatment approach may be needed if you have:
- A history of pancreatitis
- Gallbladder disease or gallstones
- Severe gastrointestinal disease, such as gastroparesis (delayed stomach emptying)
- Type 1 diabetes
- Diabetic retinopathy (eye disease caused by diabetes)
- Significant kidney or liver disease
- A personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2 (MEN2)
- Planned surgery, particularly under general anaesthetic or sedation, as these medicines slow stomach emptying
This is not a complete list. Your prescriber will ask detailed questions about your health to make sure treatment is safe.
If you would like to understand the potential side effects before you decide, read our guide to weight loss injection side effects.
Medicines that may affect your eligibility
Some medicines need careful review before starting a weight loss injection.
These include:
- Insulin or sulfonylureas (such as gliclazide), because of the increased risk of low blood sugar
- Oral contraceptive pills, particularly with Mounjaro, which may reduce their effectiveness in people who are overweight or obese
- Warfarin and other medicines where small changes in absorption can matter
- Other weight loss medicines, including other GLP-1 medicines
Always tell your prescriber about every medicine you take, including prescribed medicines, over-the-counter products and supplements.
Taking a weight loss injection does not always mean you have to stop another medicine, but your treatment plan may need to be adjusted.
NHS vs private weight loss injections: are the criteria different?
Yes. The criteria for NHS treatment are currently stricter than the licensed criteria used by private prescribers.
Wegovy on the NHS
NICE recommends Wegovy on the NHS mainly for adults with a BMI of at least 35 and at least one weight-related condition, with a lower threshold for some people referred to specialist services. It is generally prescribed through specialist weight management services, and NHS treatment is limited to a maximum of two years.
Mounjaro on the NHS
NICE recommends Mounjaro for adults with a BMI of at least 35 and at least one weight-related health condition, with lower thresholds for some ethnic groups.
However, NHS access is being rolled out gradually over several years, starting with people who have the highest clinical need. This means many people who technically meet the NICE criteria are not yet able to get Mounjaro through their GP.
Private weight loss injections
Private prescribers, including online pharmacies such as SynovaMed, generally assess patients against the licensed criteria (BMI 30+, or 27+ with a weight-related condition), subject to a full clinical assessment.
Private treatment is not free. You pay for the medicine and the service. Our Mounjaro cost guide explains what to expect.
How does an online eligibility check work?
Buying weight loss injections online should never be as simple as ticking a few boxes.
In February 2025, the General Pharmaceutical Council (GPhC), which regulates pharmacies in Great Britain, introduced stricter guidance for online pharmacies supplying weight loss medicines.
Under this guidance, prescribers must independently verify a person's weight, height and/or BMI before prescribing. Relying on an online questionnaire alone is not enough.
At SynovaMed, a typical process looks like this:
1. Create an account
Register for an account and choose the treatment you are interested in.
2. Complete a medical consultation
You will be asked about your weight, height, medical history, current medicines, lifestyle and any previous weight loss treatment.
3. Verify your identity and weight
You may be asked to confirm your identity and provide evidence to verify your weight and BMI, such as a photo or video. This is a regulatory requirement designed to protect patient safety.
4. Clinical review
A qualified prescriber reviews your consultation. They may contact you with further questions, request additional information, or ask for permission to contact your GP.
5. Prescription and delivery
If treatment is clinically appropriate, your prescription is issued and your medicine is dispensed and delivered.
6. Ongoing monitoring
You will be asked to provide updates on your weight, side effects and progress before each re-order. This helps ensure treatment remains safe and effective.
If a website offers weight loss injections without any meaningful health checks, treat that as a warning sign.
Why are these checks so important?
Some people find the verification process inconvenient.
But these checks exist for good reasons.
Weight loss injections are powerful medicines. When supplied to the wrong person, they can cause harm.
The checks help to:
- Prevent supply to people who are not overweight
- Identify people with a history of eating disorders
- Identify medical conditions that make treatment unsafe
- Identify medicines that could interact
- Protect people from counterfeit or unregulated products
The MHRA has repeatedly warned the public about fake weight loss injections sold through social media, beauty salons and unregulated websites. Buying from a registered UK pharmacy with a proper prescribing process is the safest route.
What if I have already been taking weight loss injections?
If you are switching from another provider, you can usually continue treatment if it remains clinically appropriate.
Your starting BMI (before you began treatment) is relevant here. If you have already lost weight, your current BMI may be below the usual threshold.
You will normally be asked to provide evidence of your previous treatment, such as:
- Your starting weight and BMI
- The medicine and dose you have been taking
- When you last took a dose
- Evidence of previous prescriptions
This helps your new prescriber decide on the right dose. If you have missed several doses, you may need to restart at a lower dose.
What if my BMI is too low for weight loss injections?
If your BMI is below 27, or below 30 without a weight-related health condition, weight loss injections are not licensed for you.
This does not mean you cannot improve your health or lose weight.
Options may include:
- Improving diet quality and portion control
- Increasing physical activity, including strength training
- Improving sleep and stress management
- Speaking to your GP about local NHS weight management support, such as the NHS Digital Weight Management Programme where eligible
A responsible prescriber will not supply weight loss injections outside the licensed criteria simply because a patient asks.
Is there a maximum BMI for weight loss injections?
There is no upper BMI limit in the licence for Mounjaro or Wegovy.
People with a very high BMI may benefit substantially from treatment. However, they may also have more complex medical needs, so a more detailed assessment and closer monitoring may be required.
Is there an age limit for weight loss injections?
Online weight-management services in the UK generally treat adults aged 18 and over.
There is no strict upper age limit, but older adults may need closer monitoring, particularly for muscle loss, dehydration and interactions with other medicines. Our article on weight loss injections and muscle loss explains how to protect strength and function during treatment.
Which weight loss injection is right for me?
If you are eligible, the next question is which treatment is most suitable.
The two main options are:
- Mounjaro (tirzepatide), which acts on both GLP-1 and GIP receptors
- Wegovy (semaglutide), which acts on GLP-1 receptors
Your prescriber will consider your medical history, goals, previous treatment and preferences. You can compare them in our article: Is Mounjaro better than Wegovy?
If you would prefer a tablet rather than an injection, read Wegovy tablets vs Mounjaro and our guide to Foundayo in the UK.
Frequently Asked Questions
What BMI do you need for weight loss injections in the UK?
For private treatment with Mounjaro or Wegovy, you usually need a BMI of 30 or more, or a BMI of 27 or more with at least one weight-related health condition. NHS criteria are stricter.
Can I get Mounjaro with a BMI of 27?
Possibly, if you also have at least one weight-related health condition such as prediabetes, type 2 diabetes, high blood pressure, high cholesterol, obstructive sleep apnoea or cardiovascular disease, and your prescriber considers treatment suitable.
Can I get Wegovy with a BMI of 25?
No. A BMI of 25 is below the licensed criteria for Wegovy and Mounjaro.
Can I get weight loss injections on the NHS?
Some people can, but NHS criteria are stricter and access is limited. Wegovy is mainly offered through specialist weight management services, and Mounjaro is being rolled out gradually.
Do I need to see a doctor to get weight loss injections?
You need a prescription from a qualified prescriber. With a regulated online pharmacy, this involves an online consultation and clinical review rather than a face-to-face appointment.
Why do online pharmacies ask for a photo or video of me?
GPhC guidance requires prescribers to independently verify a patient's weight, height and/or BMI before prescribing weight loss medicines. Photo or video verification is one way this is done.
Will my GP be told that I am taking weight loss injections?
Many prescribers will ask for your consent to inform your GP, as this helps keep your medical records complete and supports your safety. If you do not want your GP to be informed, discuss this with your prescriber, as it may affect whether treatment can be offered safely.
Can I get weight loss injections if I have type 2 diabetes?
Often yes, but your diabetes medicines may need adjusting, particularly insulin or sulfonylureas, because of the risk of low blood sugar. Your prescriber will review this carefully.
Can I get weight loss injections if I am breastfeeding?
No. Weight loss injections are not recommended while breastfeeding.
Can I get weight loss injections if I have had an eating disorder?
Generally, weight loss injections are not suitable for people with a current or past eating disorder unless treatment is overseen by a specialist.
Can I be refused weight loss injections even if my BMI qualifies?
Yes. BMI is only one part of the assessment. A prescriber may decline treatment if it is not clinically safe or appropriate for you.
The bottom line: are you eligible for weight loss injections?
If you are an adult with a BMI of 30 or more, or 27 or more with a weight-related health condition, you may be eligible for private treatment with Mounjaro or Wegovy.
But eligibility is about more than a number.
A safe prescribing process should always consider:
Your BMI and waist measurement.
Your medical history and current medicines.
Whether you are pregnant, breastfeeding or planning a pregnancy.
Any history of eating disorders.
Independent verification of your weight and identity.
Ongoing monitoring throughout treatment.
If you think you may be eligible, you can start an online consultation through our weight loss programme. If you have questions before you begin, contact our team and we will be happy to help.
Medical Disclaimer
This article is intended for general educational purposes and does not replace personalised medical advice, diagnosis or treatment. Eligibility for Mounjaro, Wegovy and other prescription weight-management medicines is determined by a qualified prescriber following a full clinical assessment. Meeting the BMI criteria does not guarantee that treatment will be suitable or prescribed. NHS eligibility criteria and availability may change, so check current guidance with your GP.