Five million people in England have blood sugar levels indicating a high risk of developing Type 2 diabetes, according to a report by Public Health England (PHE).
The new estimate "further underlines" the need to act on Type 2 diabetes, which already results in 22,000 early deaths and costs the NHS £8.8billion every year.
Professor Jonathan Valabhji, National Clinical Director for Diabetes and Obesity, NHS England said: "There are too many people on the cusp of developing Type 2 diabetes and we can change that."
An evidence review also published today by PHE shows programmes can be successful in preventing 26% of people at high risk of Type 2 diabetes from going on to develop the condition.
People supported by diabetes prevention programmes lose on average 1.57kg more weight than those not on a programme aiming to significantly reduce diabetes risk.
The report was commissioned by the NHS Diabetes Prevention Programme (NHS DPP), which will support people by helping them lose weight, be more active and have a healthier diet.
Practitioners, clinicians, academics and the public are currently being consulted on a proposed outline of the programme.Consultation responses will further inform the programme, with a phased national rollout starting in 2016.
Barbara Young, chief executive of Diabetes UK, said: "Having high blood glucose levels significantly increases your risk of developing Type 2 diabetes, which is a serious health condition which affects 2.9 million people in England, and can lead to devastating complications such as blindness, amputations and stroke, and ultimately early death.
"This is why it is really important that people at high risk of developing Type 2 diabetes are given evidence-based support to reduce their risk. As well as helping to reduce the human cost of Type 2 diabetes, this would also go a long way to helping to reduce costs to the NHS.
"The NHS spends 10% of its entire budget managing diabetes and unless we get better at preventing Type 2 diabetes this figure will rise to unsustainable levels."
People identified with a high risk of developing Type 2 diabetes, either through an NHS Health Check or through an existing blood test result will be offered a place on the NHS DPP when it launches in 2016.
