Experts fear that major events such as the Olympics and the Queen's Diamond Jubilee will lead to a "significant drop" in blood donations.
NHS Blood and Transplant warned that a "perfect storm" could be created in 2012 by special events, extra bank holidays and a bumper sporting calendar.
In 2011, thousands fewer people donated blood due to bank holidays around Easter and the royal wedding, it said.
And on one day alone in 2010, there were 851 fewer donations than the previous year - a 12% drop - due to the combination of sunny weather, the football World Cup quarter final and Andy Murray's Wimbledon semi-final.
More than nine out of 10 (93%) donors give blood during the working week.
Jon Latham, assistant director for blood donation at NHS Blood and Transplant, said: "2012 is going to be an exciting year for the UK but we're concerned that the cluster of major events could dramatically impact the number of blood donations coming in.
"Approximately two million units of blood will be needed by hospitals throughout 2012, and the equivalent of 500 extra donations will be needed each week in the first six months to help us build blood stocks and cover extra potential need from Olympic visitors.
"We're calling on the public to make regular blood donation a new year's resolution. Whether you've never donated before or haven't done for a while please book your appointment and help save lives in 2012."
TV presenter Penny Smith, who is supporting the campaign, said: "Giving blood is simple for the donor but it's life-changing for the patient who receives it. Some 7,000 donations are needed every day to make sure there's enough blood for those who need it. Make your new year's resolution a lifesaving one - give blood."
Other celebrities supporting the 2012 new year resolution campaign include singer Sophie Ellis-Bextor, comedian Dave Spikey, athlete Jo Pavey, Dancing on Ice star Jayne Torvill, Olympic bob skeleton winner Amy Williams, Derby County football manager Nigel Clough, former rugby league player Steve Prescott and TV presenter Ben Fogle.