According to statistics published today by the National Records of Scotland, there were 706 drug-related deaths in 2015, up from 613 in 2014 and more than double the figure for 2005 (336).
People aged between 35 and 44 accounted for more than a third of the deaths - the biggest of any age group.
Nearly a third of deaths were in the Greater Glasgow and Clyde NHS board area, while 14 per cent were in Lothian.
Commenting on the findings, public health minister Aileen Campbell said: "These figures show that we have an ageing group of drug users who are experiencing increasingly poor health. This is a legacy of Scotland’s drug misuse which stretches back decades.
“To address this we have funded research to investigate the issues associated with older drug users through the Scottish Drugs Forum. We have also achieved significant reductions in treatment times for those needing treatment for their drug problem.
“We remain committed to tackling the scourge of illegal drugs and the damage they do to our communities, and to support those who are struggling with addiction.”
Dave Liddell, director of the Scottish Drugs Forum, added: “The increase in fatal drug overdoses is a wake-up call to redouble efforts to reduce this tragic and largely preventable loss of life.
“Recently there has been increasing activity focussed on particularly vulnerable groups of people, for example the ageing cohort of drug users. The Scottish Drugs Forum (SDF) was commissioned by the Scottish Government to undertake work in this area and to look at how to improve service engagement and provision to this population.
“A report and recommendations on how services might be improved to engage more effectively with older drug users will be published later this year.
“Alongside this, SDF have been commissioned to undertake a wider piece of work supporting the local planning groups, Alcohol and Drug Partnerships, to develop death prevention strategies for their areas. This work recognises that death prevention is key to people making significant progress in their lives in terms of their health, well-being and being active within their communities.”