Police and McDonald's says they are looking at claims posted online by two people who said they found prescription pills in their shakes bought from Te Atatu McDonald's.
"We ate them at home, and we all found traces and whole pills of prescription medicine ... My sister ingested one ... I found one in my mouth and spat it out," the complainants said on a Facebook community page.
Police have confirmed to 1 NEWS they are investigating the claims and says the "individuals took themselves to hospital to be assessed".
McDonald's says it has reviewed the CCTV from the restaurant, and told the NZ Herald "normal procedures were followed and there was nothing untoward in the filling and operation of equipment, or as the order was made and handed to the customer in drive-thru".
They are in the process of contacting the customer for further details.