YOUNG Australians getting new tattoos are partly to blame for low blood donations this year.

The Australian Red Cross turned away more than 2100 people in NSW when they went to give blood because of a little-known rule that excludes donors who have recently had a tattoo.

Across the nation, 8400 freshly inked potential donors were asked to wait the necessary six months, but only 32 per cent returned to make a donation.

The news comes as NSW battles with a low supply of blood products, especially types O and A, with the State's stockpile only two-thirds full. Australian Red Cross Blood Service spokeswoman Lisa Borges said the knock-backs were because of the service's strict rules around preventing potentially contaminated blood entering the stockpile.

She said that with more people getting themselves tattooed, especially younger people, the Red Cross was being forced to turn away blood products it could desperately use, as each of those 2100 deferred donations could save three lives.

"We need 1500 whole blood donations a week in NSW, and currently we're sitting on 1200 to 1300," Ms Borges said.

"If we had a big disaster, we could manage - but to be comfortable, we would like to have a six-day supply."

The blood service tests each donation for diseases and viruses, including HIV/AIDS, hepatitis C, hepatitis B and malaria, among other serious ailments.

It's now six months because we've got better testing to detect viruses," Ms Borges said."Only three per cent of the Australian population donates blood, but roughly 30 per cent will need a blood donation during their lives."

Other exclusions include people who lived in Britain for six months or more between 1980 and 1996; those under 16 and over 70; pregnant women or those who have given birth in the past nine months ; people with serious heart conditions; and those who are low in iron.

Go to www.donateblood.com.au or call 13 14 95.