The number of people with diabetes in the UK has reached an all-time high of 3.9 million, according to the latest figures.
Diabetes UK said there were 3,333,069 adults registered with diabetes in 2013/14, an increase of more than 125,000 adults compared to the previous year - equivalent to the population of Norwich.
As many as 590,000 people are estimated to have undiagnosed type 2 diabetes, the most common kind, which is linked to increasing levels of obesity, unhealthy diets and a lack of exercise.
There is no way of preventing type 1 diabetes, which occurs as a result of the body being unable to produce insulin and usually develops in childhood, affecting 10% of sufferers.
The charity said that with so many people now living with the condition, the NHS needs to prioritise giving them the education they need to manage their diabetes well.
If not, it can result in devastating health complications, including amputation, blindness and stroke.
The condition also costs the NHS nearly £10 billion, 80% of which is spent on managing avoidable complications.
Diabetes UK director of policy Bridget Turner said: "Over the last decade we have seen the number of people with diabetes rising at an alarming rate and these latest figures are a stark call to action - we must act now or face the very real danger of diabetes devastating the lives of even more people, and threatening to wreck the already over-burdened NHS.
"There is a gaping hole when it comes to diabetes education because we know that most people newly diagnosed with diabetes are not offered a group education course.
"This is despite strong evidence that giving people the knowledge and skills to manage their diabetes effectively can reduce their long-term risk of complications.
"We must get better at offering education to people who are living with diabetes and help them to manage this serious, complex and often overwhelming condition. It is crucial that education is made available both at the point of diagnosis and beyond as the education needs of people already living with the condition can change over time."