There is a "huge amount" to be done to raise awareness of diabetes, Theresa May said as she faced calls to sustain investment to tackle the condition.
The Prime Minister, who has Type 1 diabetes, said more needed to be done to help people manage the illness or prevent those at risk developing it in the first place.
She was speaking at the official opening of Diabetes UK's headquarters in east London as the charity called for ministers and the NHS to improve the take-up of life-saving education courses.
The visit, on World Diabetes Day, saw Mrs May talk to staff manning the charity's helpline and people living with the condition.
The Prime Minister said there was still a "job to do to make sure that everybody knows it is not just about sugar, it is about blood sugar".
Mrs May said helping people manage the condition would save the NHS money because they would not develop the life-threatening complications that can occur when diabetes gets out of control.
She told staff and guests at the charity: "There is a huge amount to be done in terms of awareness, a huge amount to be done in terms of helping people who are at risk of becoming diabetic to know what they can do so that they don't - they can change their lifestyle and change their futures.
"Helping those people who are managing with diabetes, to be able to manage it on a day-to-day basis, such that complications don't occur.
"Because, as we all know, that's a benefit not just to people, to the individuals themselves, it's a benefit to society as a whole because of the amount of money the NHS spends each year on complications that arise from diabetes."
Diabetes UK has called on the Government and NHS to address low take-up of diabetes education courses, setting a target of at least half of those with the condition taking part by 2020.
The charity's chief executive Chris Askew said: "Diabetes is a killer. It's a serious condition with serious, life-threatening complications. And it's the fastest growing epidemic of our time."
He added: "Significant investment in diabetes care and prevention by UK and national governments and the NHS, begins to recognise the scale of the challenge.
"This needs to be sustained to provide enough effective care for everyone living with diabetes and tackling the rapid rise of Type 2."