What BMI do I need for weight-loss injections in the UK?

What is BMI?

BMI stands for Body Mass Index. It is a calculation that uses your height and weight to estimate whether you are underweight, a healthy weight, overweight, or obese.

The formula places you into a category rather than measuring body fat directly. This makes BMI a screening tool, not a diagnosis.

BMI categories for adults are:

• Under 18.5: Underweight

• 18.5 to 24.9: Healthy weight

• 25 to 29.9: Overweight

• 30 or above: Obese

These categories help clinicians assess health risk at a population level.

Why is BMI used for weight loss injections?

Weight loss injections such as GLP-1 treatments are prescription medications. This means clinicians must follow clear medical guidelines to ensure treatment is appropriate and safe.

BMI is used because:

• It provides a consistent clinical threshold

• It is widely recognised in medical guidance

• It helps identify people at higher risk of weight related health conditions

BMI alone does not tell the full story, but it is a useful starting point for determining eligibility.

What BMI do you need for weight loss injections?

In the UK, weight loss injections are typically prescribed if:

• Your BMI is 30 or above

• Or your BMI is over 27 and you have weight related health conditions

These conditions may include high blood pressure, type 2 diabetes, raised cholesterol, or sleep apnoea.

Final eligibility is always confirmed through a clinical assessment, not BMI alone.

Is BMI the only factor considered?

No. BMI is only one part of the decision.

Clinicians also look at:

• Medical history

• Current medications

• Previous weight loss attempts

• Risk factors and contraindications

• Lifestyle and readiness for treatment

Someone may meet the BMI criteria but still not be suitable for treatment. Equally, someone close to the threshold may be assessed carefully if other risk factors are present.

Limitations of BMI

BMI is useful, but it has limitations.

It does not account for:

• Muscle mass

• Body composition

• Fat distribution

• Individual metabolic health

Two people with the same BMI can have very different health profiles. This is why BMI is used as a guide, not a standalone rule.

How GLP-1 injections support weight loss

GLP-1 treatments help regulate appetite by mimicking a natural hormone involved in hunger and fullness.

They work by:

• Reducing appetite

• Increasing feelings of fullness

• Slowing digestion

• Supporting a calorie deficit over time

This can make weight loss more achievable for people who have struggled with hunger, cravings, or repeated weight regain.

How Otto assesses eligibility

Otto is a clinically guided digital weight loss service operating under a UK registered pharmacy.

Eligibility is assessed through:

• A structured medical questionnaire

• Review by a qualified clinician

• Consideration of BMI alongside wider health factors

Treatment is only prescribed when it is safe, appropriate, and clinically justified.

What happens if you do not meet the BMI criteria?

If you do not meet the BMI requirements, weight loss injections will not be prescribed.

This is to protect patient safety and ensure medications are used responsibly. In some cases, alternative guidance or next steps may be recommended based on your goals and health profile.

Final thoughts

BMI is an important starting point when considering weight loss injections, but it is not the whole picture.

A BMI of 30 or above, or over 27 with related health conditions, is typically required. However, final eligibility depends on a full clinical assessment that prioritises safety and long term health.

If you are considering weight loss injections, choosing a service that looks beyond the scale and provides proper clinical oversight is essential for achieving sustainable results.