Chinese factory closures have forced Pharmac to limit the amount of government-funded paracetamol patients can be prescribed.
The main site for the manufacturing of the drugs is in China, which is currently being affected by quarantine and other restrictions as a result of Coronavirus.
Pharmac director of operations Lisa Williams said it was only a matter of time before the virus would impact their supply chain.
The new changes, which go into effect on Monday, will reduce the amount that can be prescribed to you by a health professional, except where needed for chronic use.
They are also putting in place monthly dispensing arrangements for funded paracetamol, rather than every three months.
New Zealanders will still be able to buy as much as they need without a prescription.
Pharmac said it currently has enough stock in New Zealand to meet four months of normal demand. But they are not sure when the issue will be fixed.
"Impacts to the supply of paracetamol is a global issue and we don’t know yet when normal supply of this raw material will resume. The supplier will continue to update us regularly, and once supply resumes dispensing will return to normal," Williams said.