It is not known if the tablets, found in 38 pharmacies, are toxic
More than 130,000 fake Panadol tablets and other western and herbal medicine have been seized in raids this week.
Tests are under way to determine the ingredients used in the fake medications, worth $1.24 million, and whether they are harmful.
Keith Wong Wing-fai, chief of the customs department's trade descriptions investigation unit, said 28 people were arrested during the two-day operation.
Most of the counterfeit medicine was labelled as Panadol. Officers also seized fake Golden Throat herbal candies, Pak Fah Yeow herbal oil, Tai Wo Tung cough pills and Curcyrin medicated powder.
The counterfeit medicine was found when more than 80 officers raided premises in Western and 38 pharmacies across Hong Kong.
Mr Wong urged consumers to check packages carefully when buying medicine, saying the fake Panadol pills were easy to spot.