A national blood shortage has prompted the American Red Cross to ask people everywhere to donate blood immediately. Virtually all of the Red Cross' 36 blood services regions report shortages and are appealing for donations.

Los Angeles, Philadelphia, Washington D.C., Baltimore and Detroit are some of the hardest-hit areas. While there has been an increase in donations this year, higher demand is causing the summer blood shortage.

Other contributing factors include educational institutions being on summer vacation. Students, teachers and administrators account for about 15 percent of Red Cross blood collections annually.

While it takes an average of less than one hour to donate blood, only five percent of Americans go through with the procedure. The Red Cross collects blood from about 4.5 million volunteer donors each year and provides more than 6 million units of blood to patients nationwide.

All eligible donors -- people at least 17 years old who weigh more than 110 pounds and are in good health -- are encouraged to call 1-800-GIVE-LIFE (1-800-448-35433) to schedule a donation appointment. For more information, visit the Red Cross' Web site at http://www.redcross.org.