There are a quarter of a million sufferers north of the Border, and the number of new cases has risen by more than 25% since 2006, according to Diabetes UK Scotland.
The organisation warned in a report that the NHS faces an increasing financial burden to treat people with the condition, with the annual cost forecast to balloon from £87 million this year to £146m by 2030.
It also predicts that the number of diabetics living north of the Border will grow to 350,000 during the same period unless measures are introduced to bring the disease under control.
The findings are revealed in the charity's latest State of the Nation report.
It states that there are 258,570 diabetics in Scotland, a figure its national director Jane-Claire Judson described as "truly shocking".
Ms Judson said: "Diabetes continues to be a major challenge for the NHS in Scotland.
"Add to that the numbers of people who have diabetes but have not been diagnosed and the scale of the challenge is clear."
Scotland has the third highest incidence of Type 1 diabetes in the world, and this is likely to rise as the population grows older and people with diabetes live longer.
Two-and-a-half times more people have diabetes than all cancers combined.
Mortality rates for patients with Type 1 are double that of the general population, while for those with Type 2 the risk is 1.6 times greater.
The report says that the areas in Scotland where the disease is most prevalent are Lanarkshire, Ayrshire and Arran, Dumfries and Galloway and the Western Isles.
Four out of five people with Type 1 diabetes have poor control of their condition, and complications from diabetes can include heart disease, sight loss, lower limb amputation and kidney failure.
Dr David Haslam, chairman of the National Obesity Forum, said that it would take a massive effort to bring diabetes levels down.
He said: "In 90% of cases, diabetes is weight-related and numbers are going to keep going up as the population get older and fatter.
"We need to have a complete change in our attitudes right down to urban architecture.
"We should not walk into a supermarket and see rows upon rows of fizzy drinks or sweets at the till. These should be replaced with healthy products.
"When I walk into a hotel I should see the stairs right in front of me, attractively laid out, not be directed to the lifts. Because treating people on a one-to-one basis, day after day, as I do, is not going stop the epidemic."
The report comes as politicians prepare to draw up a new national framework to determine how the NHS in Scotland tackles diabetes.
The previous Scottish Diabetes Action Plan, drawn up in 2010, has come to an end although its work continues to be observed until new guidelines are issued.
A Scottish Government spokesman said: "Our Diabetes Action Plan sets out a clear commitment to the prevention and early detection of diabetes and to improve the treatment and care of people with diabetes.
"For example, the Scottish Government's recent investment of £2.5m in insulin pump therapy for young people living with Type 1 diabetes will help ensure they can access this life-changing treatment.
"There are many examples of excellent care and service improvements in diabetes in all areas of Scotland, but the number of people developing diabetes continues to increase and there is certainly more to be done to ensure all people with diabetes are receiving the care they need."
He said the government will be bringing forward plans in the new year to ensure that improvements to care for sufferers can continue.