A jump in the number of people getting "inked" with tattoos has put a dent in the number of blood donations.
The Australian Red Cross says there's been a 30 per cent drop in the number of blood donors in the past seven years, citing an increase in tattoos as a major factor.
Those getting new tattoos must wait at least six months before donating blood because of an increased risk of hepatitis C infection.
To combat the fall in donors, the Red Cross has joined a global campaign called Missing Type, which launched on Tuesday.
Throughout the week-long campaign the letters of the main blood groups - A, B and O - will disappear from signs, planes, post office boxes and elsewhere throughout NSW to help raise awareness about giving blood.
"In Australia there is a particular need for 100,000 new donors this financial year to help service the growing need for plasma-based medicines that thousands of Australian patients depend on for quality of life," the Red Cross said in a statement.
In Australia, the number of donors slipped from 127,000 in 2008 to 87,000 in 2015 - a 31 per cent drop.
As well as tattoos, other factors believed to be affecting donor levels include people travelling to more exotic locations around the world, having less free time, and not being aware of the need to donate blood.
A Red Cross spokeswoman said while all blood donations are tested for infections, there's a small chance that something gets missed.
"We test all of the blood but there is no testing that is 100 per cent perfect," the spokeswoman told AAP.
