The American Red Cross Blood Services is requesting blood donors due to a critically low supply of blood in Massachusetts and across the nation.”In May and June donations were 6 percent lower than the typical national level for this time period,” Red Cross spokesperson Jecoliah Ellis said, adding that lack of donors resulted in a shortfall of 87,000 units of blood. “Donations are at the lowest level we’ve seen in a dozen years during this time frame, but the demand was the same.”This time of year is particularly tough for blood donations because school is out of session and people are often out of town for vacation, according to Ellis. And while donations have decreased, the Red Cross has responded to more than 40 major disasters in more than 30 states in the past three months alone, including the string of tornadoes that tore through Western Massachusetts in June.”On top of the shortage in May and June, we saw a 6 percent increase in demand during the first two weeks in July and donations during that time were again lower than we expected,” Ellis said. “With the heat wave and high temperatures that we’re experiencing we’re worried that we’ll have an even bigger decline.”Ann Toroyan, the blood bank manager at Beverly Hospital, added that all types of blood are needed but O negative is especially important, as it is the universal type and can be used to treat any patient.”During a trauma before we know what blood type the patient is we have to use O negative,” Toroyan said, noting that accidents are more common in the summer, as people are more active. “Having the trauma center at the hospital, keeping O negative on the shelves has been quite the challenge. Elective surgeries that aren’t an emergency obviously come after traumas, so when there’s a shortage we sometimes have to reschedule surgeries, which is an inconvenience to everyone.”In Massachusetts the Red Cross must receive at least 650 donors or 22,000 units of blood each weekday to provide the lifesaving blood demanded by 73 of the Bay State’s hospitals. As a result, even just one slow donation day could mean the difference between life and death for someone in need of blood.”When one hospital is short, we’re all short. It’s a team effort to utilize resources, but when it gets tight it’s scary,” said Toroyan.The Red Cross is asking for assistance from both previous and new donors. According to Ellis, a typical donor can give blood every 56 days and donors who just give platelets can donate 24 times a year, or every two weeks. Since one pint of whole blood supplies two or three of the four types of blood products for transfusions – red cells, platelets, plasma and cryoprecipitate – each donation can help save up to three lives. Individuals who are 17 years of age, meet weight and height requirements and are in generally good health may be eligible to give blood.”A small portion of eligible donors actually donate,” Toroyan said. “It’s a very selfless act that can touch a lot of lives. For some people it’s the difference between life and death.”