The World Health Organization calls for more people to donate blood regularly.
"Every year, millions of people rely on the generosity of another person to donate blood," the WHO said. "Yet, blood donation rates vary considerably and the demands for blood and blood products are increasing worldwide."
"To meet these needs, more people must come forward to give blood voluntarily, and regularly," it added.
"With increasing life expectancy and the subsequent increase in the number of age-related, chronic diseases, including cancers, that require blood and blood products for treatment, demand outstrips supply," warned Dr Neelam Dhingra, coordinator for blood transfusion safety at the WHO.
"In addition, some blood products used to treat cancer patients, like platelets, have a shelf-life of only five days. This means we increasingly need more blood donors to meet these demands."
The WHO said 92 million blood donations were made every year "globally, most of these by voluntary, unpaid donors.
"But of these voluntary donors, 30 million give blood once, and then do not return."
"We need to encourage these donors to come back and become repeat, regular donors," Dhingra said.
"Each blood donation is only 450 millilitres and by having more repeat voluntary donors, we can better assure the reliability of blood supply and safety of blood and blood products."
The WHO said the need for blood and blood products was rising in all parts of the world.
Every year, road traffic accidents cause 1.3 million deaths globally and, in addition, injure or disable between 20 million and 50 million people. Uncontrolled bleeding accounts for more than 468,000 deaths per year.