Hundreds of illegal and potentially deadly sex and weight-loss pills are being brought into the country.
Medsafe figures show that since 2009 Customs has seized more than 1000 adulterated products claiming to be herbal, but contain prescription medicines, as well as more than 100 erectile dysfunction drugs that have no active ingredient but purport to contain prescription medicines.
The medical safety regulator says there is no way for people buying pills over the counter or via the internet to tell whether they are legitimate.
Spokesperson Derek Fitzgerald says adulterated and counterfeit pills contain unknown ingredients which can cause harmful reactions and sometimes result in death.
He says people buying over the internet are sometimes fooled into thinking the pills are New Zealand-made when in fact they're manufactured in countries like China.
Figures obtained by Radio New Zealand show a huge volume of illegitimate products is arriving at the border, most of them weight-loss pills.
Medical Council chairperson Paul Ockelford says people should not trust what they read on the packets, as it is often wrong.
He says men wanting to treat erectile dysfunction should not feel ashamed, and should consult a doctor.