Health officials are warning a shortage of anti-psychotic drug - olanzapine , could cause relapses for people with schizophrenia symptoms

Supply of the injected medication is already low - and a shipment didn't arrive last month.

Royal College of Psychiatrists New Zealand chair, Hiran Thabrew says it's critical for people to get their regular medication, or a substitute.

He says without the medicine they could experience a deterioration in their mental state, reccurring psychosis, and possible behaviour changes.