Tasmanians can now access medicinal cannabis via prescription, and this medication may contain tetrahydrocannabinol (THC), cannabidiol (CBD), or a mixture of both, depending on what is prescribed by the GP.

Under Tasmanian road safety laws, a person found driving with THC in their saliva or blood, which is affecting their ability to drive, may be found guilty of an offence.

Tasmania Police said roadside oral fluid drug testing will test for THC, but there was no way to determine whether a positive oral fluid test related to prescription or illicit use of cannabis.

"Legislation differs across states and territories regarding the use of medicinal cannabis and driving," Tasmania Police said.

"In many jurisdictions, it is an offence to drive with THC present in a person's oral fluid or blood. In those instances, there is no legislative dispensation or defence for the use of medicinal cannabis which leads to a positive road drug test."

Under Tasmanian law, THC is seen as a prescribed and lawful drug but a person does not commit an offence if that drug was obtained and administered lawfully.

"Therefore, if a person is lawfully using medicinal cannabis, that person does not commit an offence in respect of driving with a prescribed illicit drug present in their oral fluid/blood ...this is also the case for licit use of opioids," the Police said.

However, there may still be an offence if a person's driving is so affected by the drug that they are incapable of having proper control of the vehicle.

"There are many prescribed medications which have the capacity to affect driving, therefore this principle is not limited to cannabis only," the Police said.

"Tasmania Police is consulting with other policing jurisdictions to enquire what, if any legislative or policy change has been undertaken to address the use of medicinal cannabis while driving a vehicle and will assess the ongoing legislative response in Tasmania."