Broadly: a BMI of 30 or above, or 27 or above with a weight-related condition such as type 2 diabetes, hypertension, sleep apnoea or fatty liver. Medical history is assessed before any prescription.
The BMI thresholds
The standard framework is a BMI of 30 or above, or 27 or above where a weight-related health condition is present.
BMI is a starting point, not the whole picture. It does not distinguish muscle from fat, and it under-reads risk in some South Asian populations, which is why waist measurement and metabolic markers are assessed alongside it.
Qualifying weight-related conditions
Type 2 diabetes or pre-diabetes, high blood pressure, high cholesterol, obstructive sleep apnoea, non-alcoholic fatty liver disease, PCOS and weight-bearing joint disease are all commonly considered.
Where these are present, the threshold for treatment is lower, because the health benefit of weight reduction is greater.
BMI reference
| Below 18.5 | Underweight — treatment not appropriate |
| 18.5 to 24.9 | Healthy range — not indicated |
| 25 to 26.9 | Overweight — generally not indicated |
| 27 to 29.9 | Considered where a weight-related condition is present |
| 30 to 34.9 | Obesity class I — generally eligible |
| 35 and above | Obesity class II/III — eligible; surgery may also be discussed |
What else is assessed
Your full medication list, since some drugs require adjustment. Your history of weight loss attempts. Blood work covering thyroid, glucose, liver function and vitamin levels.
Your doctor is also assessing whether you are in a position to engage with the nutrition and follow-up side, because the medicine alone rarely delivers a lasting result.
Who cannot take these medicines
A personal or family history of medullary thyroid carcinoma or MEN2 syndrome rules them out. So does a history of pancreatitis, pregnancy, breastfeeding, and planned pregnancy in the near term.
Certain gastrointestinal conditions, severe kidney impairment and some medication combinations also require careful review or exclude treatment.
If you do not qualify
There are other routes. A dietitian-led programme, the Allurion swallowable balloon, or bariatric surgery may be more appropriate depending on your BMI and health.
We would rather tell you honestly that a treatment is not right for you than prescribe something inappropriate.
Why BMI alone is imperfect for South Asians
Research has consistently shown that South Asian populations develop metabolic complications at lower BMI thresholds than European populations, due to differences in body fat distribution and visceral fat.
Some guidance therefore applies lower thresholds for South Asian patients. Waist circumference and metabolic markers are assessed alongside BMI for this reason.
Adolescents and older adults
Prescribing in patients under eighteen is a specialist decision made under specific guidance, not routine practice. Age alone does not exclude older adults, but frailty, muscle mass and polypharmacy require careful assessment.
In older patients particularly, protecting muscle during weight loss becomes a primary consideration rather than an afterthought.
Pregnancy and fertility
These medicines are not used in pregnancy or while breastfeeding, and are typically stopped a defined period before planned conception. Your doctor will advise on timing.
Weight loss can restore ovulation in women with PCOS, meaning fertility may return unexpectedly. Contraception should be discussed before starting.
Frequently asked questions
What BMI do I need for weight loss injections?
Can I get them if my BMI is 25?
Does PCOS qualify?
Do I need diabetes to qualify?
How do I find out if I qualify?
Medical disclaimer. This article is general information, not medical advice, and does not replace consultation with a qualified doctor. The medicines discussed are prescription-only and must be prescribed and monitored by a physician. Outcomes vary between individuals. Never start, stop or change a prescribed medicine without medical advice.