An official at the ministry said the capacity of rehabilitation centers countrywide has increased to over 40,000 patients, from 2,000 five years ago.
The official said that in order to overcome the problem, there is a need to curb drug trafficking.
"These 2.5 million are in 34 provinces of Afghanistan, mostly in villages rather than urban areas," he said, adding: "Widespread precautionary measures are required to curb drug addiction."
He suggested that job opportunities and facilities for entertainment and sports should be provided for youth to keep them away from drugs.
Kabul has many areas where drug addicts are often seen. One of these drug addicts, Ali Reza, 28, said they have "easy access" to drugs in the city and that he became an addict when he was 13.
"I want to be treated. I want to rejoin the society," he said.
"I have not visited any rehabilitation center because people say that these centers are not providing good services," said Nawroz, a drug addict.
The presence of drug addicts in some Kabul streets has created problems for residents.
"People’s belongings are stolen. People have complaints. They are tired of them (presence of drug addicts)," said Mohammad Hussain, a Kabul resident.
"There is a need for proper action by the government against narcos," said Rajab Ali, a Kabul resident.
Afghanistan has been among the world's top illicit drug-producing countries.
Reports indicate that poppy cultivation and drug trafficking provides a big income source for the Taliban
...mindless ferocity in a turban..., mainly in the southern and northern parts of the country.