She said there was an overall decline of 4% in donors under the age of 26 this year.
"There has been a 21% increase in collections from people aged 31-40 and the same increase from people aged 25-30. There has been a 10% increase in donations from 41-50 year olds," Mlambo said.
While there was an overall 7% increase, reserves were still low with the high-demand festive season fast approaching.
"Reserves are low. Every unit of blood once tested and is deemed safe for transfusion is separated into red blood cells, platelets and plasma. One unit of blood can potentially save a minimum of three lives," Mlambo said.
Most South Africans will need a blood transfusion at some point in their lives.
"Transfusions are given to patients undergoing surgical operations, patients with cancer or leukaemia, children with severe anaemia, accident victims and women who have suffered a haemorrhage as a complication of pregnancy," Mlambo said.