North Wales Police and Betsi Cadwaladr University Health Board are warning people about the danger of a form of ecstasy called "Green Apples", after the death and serious illness of two local men.
A 19-year-old man from Llangefni died on Saturday after suspected drug use.
Two weeks ago, a 19-year-old man from Bangor was admitted to intensive care after he had taken controlled drugs, but he survived.
The number of deaths linked to drugs and drink in Wales have increased by 31% in 10 years, compared with 15% in England.
Figures show 496 people died as a result of drug or alcohol use in 2010 here. In 2001 that figure was 380.
The rate of deaths from avoidable causes remains higher in Wales than in England, although it has fallen by almost a quarter over the 10 years.
The leader of a major North Wales drugs network has been sentenced today for running a sophisticated network from inside his prison cell. Paul David Williams and the other 21 members of his gang have been jailed for a total of 124 years.
A group of 23 drug dealers, led by a man from his prison cell, have been jailed for a total of 124 years and 11 months at Caernarfon Crown Court.