New figures released later are expected to show that more than 1,000 people died as a result of drugs in Scotland last year.
Scotland already has the worst record for reported drug deaths in Europe but the latest figures will show another steep rise.
Last week, Scottish Public Health Minister Joe Fitzpatrick said the level of drug deaths was an “emergency”.
He told MPs this should be a “wake-up call” over UK government policy.
Drug-related deaths in Scotland have almost doubled in eight years, with 934 recorded in 2017.
There are estimated to be more than 60,000 problem drug users in Scotland, which has a population of five million.
Dr Saket Priyadarshi, of NHS Greater Glasgow and Clyde addiction services, told MPs last week that Scotland had more than twice the rate of drug deaths as the rest of the UK because it had far more problem users.
He also said that Scottish users were taking a lethal cocktail of drugs that often combined opiates such as heroin and methadone with benzodiazepines, pills often known as street valium or street blues.
Most drug-related deaths involved heroin but a large percentage had also taken pills.
More than three-quarters of deaths due to drugs in 2017 were of people aged 35 and over.
Dr Priyadarshi said there was an ageing population of drug addicts, mainly men, who had been using heroin for decades and were now also taking new street pills, often containing etizolam which is stronger than prescription benzos.
It said Germany, Spain, Switzerland, Canada and, most notably, Portugal were among 25 nations to loosen the punitive attitude to drug possession to enable treatment programmes to succeed.
‘I lost my mum, dad, two sisters and brother to drugs’
Jacquie, from Glenrothes in Fife, has told how her father, mother, two sisters and brother all died because of drugs.
She said losing her parents and siblings “was like a fire ripping through my family”.
She was speaking ahead of new figures which are expected to show that the number of people who died of drugs in Scotland in 2018 reached more than 1,000.
Jacquie, 34, is herself a recovering drug addict.
She told BBC Scotland’s The Nine: “It is scary how quick it can take a grip and devastate a family.
“I feel my life has been ruined.
“People could say that has been my fault, I understand that with the drug side. I can’t help the fact that I have lost all my family to the drugs. And it is hard.”
Jacquie, who began taking heroin at the age of 17 and is now trying to kick the habit, said she could not remember a time when the family wasn’t affected by drugs.
She is the last remaining member of her immediate family – who all lived and died in the Fife town of Glenrothes.
The woman leading the Scottish government’s new drugs taskforce, Prof Catriona Matheson, told BBC Scotland the evidence for decriminalisation was strong.
She said: “It is about not putting these marginalised drug users into prison because that further marginalises them and that makes the recovery all the more difficult.”
During evidence to the Scottish Affairs Committee, Mr Fitzpatrick praised the “bold move” taken in Portugal to decriminalise drugs but said his government in Scotland was unable to make changes as drugs policy was reserved to Westminster.
Glasgow City Council’s plan for users to be able to take their own drugs under the supervision of medical staff at a special facility in the city would also need a change in UK law.
The Home Office has refused permission for Glasgow to set up the so-called “fix rooms”, where users could inject heroin or cocaine in a safe and clean environment.
It was hoped the special room would encourage addicts into treatment, cut down on heroin needles on city streets and counter the spread of diseases such as HIV.