In short: In the UK, NICE recommends that adults with a BMI of 40 or more, or a BMI of 35 to 39.9 with a significant weight-related condition such as type 2 diabetes or high blood pressure, are offered an assessment for weight loss (bariatric) surgery. People with recent-onset type 2 diabetes may be considered at a lower BMI, and thresholds are 2.5 points lower for some ethnic groups. You must also be fit for surgery and willing to commit to lifelong follow-up.

This guide, written by a Ready Health prescribing pharmacist, explains the current NICE criteria, what the assessment involves, the main types of surgery and how to explore your options from Standish, Wigan and the surrounding area.

What is weight loss surgery?

Weight loss surgery, also called bariatric or metabolic surgery, changes the stomach and sometimes the small intestine so that you feel full sooner and eat less. It also changes gut hormones that affect appetite and blood sugar. It is a major treatment, not a quick fix, and it works best as part of a long-term plan that includes changes to eating, activity and regular check-ups.

Who qualifies for weight loss surgery under NICE guidance?

NICE guidance on overweight and obesity management (NG246) sets out when an assessment for bariatric surgery should be offered or considered.

Your situation	NICE position
BMI of 40 or more	Offer a referral for assessment for surgery
BMI of 35 to 39.9 with a significant weight-related condition (for example type 2 diabetes, high blood pressure or obstructive sleep apnoea)	Offer a referral for assessment for surgery
BMI of 35 or more with type 2 diabetes diagnosed in the past 10 years	Offer an expedited (faster) assessment
BMI of 30 to 34.9 with type 2 diabetes diagnosed in the past 10 years	Consider an assessment for surgery

For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, NICE advises using thresholds 2.5 BMI points lower, because health risks such as type 2 diabetes tend to rise at a lower BMI in these groups.

Older guidance said people had to try all non-surgical options and complete a specialist (tier 3) weight management programme before surgery. NICE removed that as a strict requirement in 2023, although you will still be assessed by a specialist team and local NHS pathways can vary.

What else is checked before surgery?

Meeting the BMI criteria is only the first step. A multidisciplinary team, usually including a surgeon, dietitian, psychologist and specialist nurse, will look at:

Physical fitness for surgery: whether you are well enough for a general anaesthetic and to recover safely, including heart and lung health
Medical conditions and medicines: including diabetes treatment, blood thinners and any medicines that may need adjusting
Nutrition and eating patterns: to plan the dietary changes needed before and after surgery
Psychological readiness: conditions such as depression, an eating disorder or alcohol or substance misuse do not always rule surgery out, but they need to be stable and well supported first
Commitment to follow-up: lifelong vitamin and mineral supplements, regular blood tests and check-ups are essential after most procedures

What are the main types of weight loss surgery?

Sleeve gastrectomy: a large part of the stomach is removed, leaving a narrow tube-shaped stomach.
Gastric bypass: a small stomach pouch is created and connected directly to the small intestine, bypassing most of the stomach.
Gastric band: an adjustable band is placed around the top of the stomach. Bands are now used less often in the UK than sleeve or bypass operations.
Gastric balloon: a balloon is placed in the stomach using an endoscope rather than surgery. It is temporary, usually removed after around 6 to 12 months.

Your surgical team will explain which option may suit you, along with its benefits and risks.

What are the risks?

All surgery carries risks. Possible complications include bleeding, infection, blood clots, leaks where the stomach or bowel has been joined, gallstones, nutritional deficiencies, and dumping syndrome after a bypass. Some people also experience changes in mood or relationships with food. Many people see major improvements in weight and in conditions such as type 2 diabetes, but results vary and are not guaranteed.

Can I have weight loss surgery on the NHS?

Yes, if you meet the criteria, although availability and waiting times vary across the UK. Your GP can discuss referral to a specialist weight management service. Some people choose to have surgery privately, and the same safety checks and aftercare are still important. If you have surgery abroad, make sure you understand how follow-up care will work when you return.

Frequently asked questions

What BMI do you need for weight loss surgery in the UK?

Generally 40 or more, or 35 or more with a weight-related health condition. People with type 2 diabetes diagnosed in the last 10 years may be considered from a BMI of 30, and thresholds are 2.5 points lower for some ethnic groups.

Do I have to try other weight loss methods first?

NICE no longer makes this a strict requirement, but your team will discuss non-surgical options such as diet, activity, behavioural support and, where suitable, medicines.

Is a gastric balloon the same as surgery?

No. A balloon is placed through the mouth using an endoscope and is temporary. It is not usually available on the NHS.

Will I need supplements after surgery?

Most people need lifelong vitamin and mineral supplements, especially after a bypass or sleeve, and regular blood tests to check for deficiencies.

Key takeaways

NICE recommends surgery assessment from a BMI of 40, or 35 with a weight-related condition.
Recent-onset type 2 diabetes and ethnic background can lower the threshold.
You must be fit for surgery and committed to lifelong follow-up.
Sleeve gastrectomy and gastric bypass are the most common operations.
Surgery has real risks as well as benefits, so a specialist assessment is essential.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

If you are in Standish, Wigan or nearby and want to talk through whether surgery or another approach might suit you, you can book a weight management consultation at Ready Health. Where appropriate, we can discuss onward referral to a specialist bariatric service.