In Canada it is a criminal offence to drive impaired. One can be impaired by alcohol or drugs, including prescription medication. It is also an offence to be driving with over 80 milligrams of alcohol in 100 millilitres of blood. This legal limit is sometimes referred to as Over 80.  As far as drugs go, if one is suspected of being impaired by drugs then an officer can request that a person undergo a drug evaluation by a certified Drug Recognition Expert (DRE). The charge of Impairment by drug is becoming increasingly more prevalent in todays society including prescription medications. A related charge to these offences is also failure to provide a breath sample or failing to comply with a DRE for evaluation.