The threshold
Bariatric surgery is generally considered at a BMI of 35 or above, or from 30 where there are related conditions — type 2 diabetes, high blood pressure, sleep apnoea, fatty liver disease or significant joint problems. The reasoning is simple: those conditions change the balance between the risk of operating and the risk of not operating.
Where you stand
| Your BMI | Generally |
|---|---|
| Under 30 | Surgery not indicated |
| 30 – 34.9 | Considered if you have a related condition |
| 35 – 39.9 | Considered |
| 40 and above | Clearly indicated, assuming you are fit for anaesthesia |
To work out your own figure, divide your weight in kilograms by your height in metres squared. At 100 kg and 1.70 m that is 100 ÷ 2.89 = 34.6 — just under the main threshold, and therefore a case that turns on whether any related conditions are present.
What BMI does not tell you
BMI takes no account of how weight is distributed or of muscle mass, so it is a screening tool rather than a verdict. The assessment also weighs your medical history, how your weight has changed over time, previous attempts at losing it, your fitness for general anaesthesia, and whether you are in a position to commit to the follow-up. That last point matters more than patients expect: the operation is the start of the treatment, not the whole of it.
Things that need addressing first
Some factors do not rule surgery out but have to be dealt with beforehand — active smoking, untreated sleep apnoea, poorly controlled blood sugar, or an eating disorder. A surgeon who asks you to sort one of these out before operating is doing their job properly.
Find out for free
Send us your height, weight and any diagnosed conditions on WhatsApp. We will tell you where you sit against the threshold and which operation your case points towards — at no cost, with no obligation. If you are not a candidate, we will tell you that too.
Frequently asked questions
What BMI do I need for bariatric surgery?+
Bariatric surgery is generally considered at a BMI of 35 or above, or from 30 where there are related conditions such as type 2 diabetes, high blood pressure or sleep apnoea. The final decision always rests with the surgeon after your pre-operative tests.
How do I calculate my BMI?+
Divide your weight in kilograms by your height in metres squared. For example, 100 kg at 1.70 m gives 100 ÷ (1.70 × 1.70) = 34.6. Send us your height and weight and we will work it out and tell you where you stand, free of charge.
Can I have surgery if my BMI is under 30?+
Generally no. Below 30 the risks of an operation are not considered justified by the benefit, and reputable surgeons will decline. If a clinic tells you otherwise without examining you, treat that as a warning sign rather than good news.
Is there an upper BMI limit?+
There is no fixed ceiling, but a very high BMI increases anaesthetic risk, and the surgeon may ask you to lose some weight before the operation to make it safer. That request is about reducing your risk, not about putting you off.
Does age affect eligibility?+
Bariatric surgery is generally performed on adults. Both younger and older patients are assessed individually, with more emphasis on general fitness for anaesthesia at the upper end of the age range.
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