MARINE CORPS BASE CAMP PENDLETON, Calif. -- Imminent large-scale deployments are coming at a bad time for local blood banks critically short of blood — a deficit that hasn't been seen in years, according to the American Red Cross. Military members are among the Red Cross' most reliable donors locally, said Stephen L. Whitburn, a spokesman for American Red Cross Blood Services of San Diego County. He encouraged military members to step forward before and during the deployment to help stem a shortage that has left local blood-collecting organizations with less than a one-day supply of most blood types for more than a month. The situation is so shaky it could return to crisis proportions — like last month, when area hospitals had to postpone some nonemergency surgeries, said Stephen L. Whitburn, a spokesman for American Red Cross Blood Services of San Diego County. "When that happens, it's a crisis," Whitburn said. "But we're a little bit better than we were." But a one-day supply could dry up after an earthquake, a major highway pileup or a terrorist attack, he said. "All it takes is one bad accident, and we're gonna go through a day's worth of blood in a big hurry," Whitburn said. "If that happens, we'd be hard-pressed to meet the need." Blood supplies dipped locally immediately after the last wave of deployments in March, especially when service members were no longer available for donations Whitburn said. But blood stockpiles are much lower now. "If local service members are (away) because of deployment, it could significantly impact our blood collection," said Whitburn, who had no statistics on what percentage of local Red Cross blood collections come from military members. During the deployment last spring, Navy medical officials asked the Red Cross to suspend blood collection on base so military stockpiles could be increased, Whitburn said. So far, no such request has been made this time, he said.Blood types most in need are A-positive, A-negative, O-positive and O-negative. "This is the worst blood shortage that we have had in three years," said Whitburn, who estimated that his organization accounts for roughly half the blood donated in San Diego County, aside from that collected by the military. The shortages mean the Red Cross cannot keep an abundant amount of blood in San Diego County hospitals. Blood stocks typically are low in winter, Whitburn said. Seasonal illnesses, bad weather and preoccupation with holiday chores deter potential blood donors, he said. But it's worse than usual this year. "The real problem is that not enough people give blood. Sixty percent of this nation is eligible to donate blood, but only 3 percent do," he said. The local Red Cross encourages military members to step up in response to the need. Service members typically are young, healthy and able to give, he said. The Red Cross of San Diego County frequently sends its blood mobile to Camp Pendleton and surrounding areas, said Doreen Rekoski, public affairs specialist and donor recruiter for Naval Medical Center San Diego. After the blood mobile receives its donations, it takes three days to screen and process the blood for patient use. Once processed, its shelf life is 42 days, Whitburn said. One blood donor theoretically can help three patients, Whitburn said. During processing, it's broken up into three different parts — red blood cells, plasma and platelets — all of which may be needed by different patients, Rekoski said. So one donor's blood might help burn and trauma victims, plus a cancer patient, Whitburn said.Donors must be at least age 17, weigh at least 110 pounds and be in good health. They must also pass screening to ensure their blood isn't infected. For a complete listing on blood mobile visits, log onto www.arcsd.org or call (800) GIVE-LIFE.