Body mass index (BMI) is commonly used in the UK, and worldwide, as part of the clinical assessment for prescription weight loss medication. It provides a simple estimate of whether excess body weight may be contributing to health risk, although it is not used on its own when making treatment decisions.

You can calculate your BMI here.
Calculate your BMI using the NHS calculator

BMI is calculated using a person’s height and weight, but other factors are always considered alongside it.

BMI Range Used in Assessment

Weight loss medication may be considered for adults who:

• Have a BMI of 30 or above, or
• Have a BMI of 27 or above with an existing weight-related health condition

These thresholds are used as general guidance rather than strict rules. Meeting a BMI threshold does not automatically mean treatment is suitable.

Why BMI Is Not the Only Factor

BMI does not account for body composition, where weight is distributed, or individual health circumstances. In simple terms, it gives a general guide of weight in relation to height. For this reason, prescribers also review medical history, current medications, and any conditions that may be affected by treatment.

Some patients with a BMI below the usual thresholds may still need further discussion, while others who meet the criteria may not be suitable due to contraindications.

How BMI Is Reviewed Online

BMI is reviewed as part of an online consultation, alongside questions about health, lifestyle, and current medication. A qualified healthcare professional reviews this information before deciding whether treatment can be prescribed.

Further details about wider suitability are available on our page:

 Who Is Eligible for Weight Loss Injections in the UK 

Weight loss medication is prescription-only and is intended to support weight management alongside lifestyle changes. All treatment decisions are subject to clinical review and eligibility.