A healthy athlete should be able to recover completely from donating blood in eight weeks, but he may lose some of his ability to train for a few days. Following a donation of one pint, blood volume is reduced by about ten percent and returns to normal in 48 hours. For two days after donating, you should drink lots of fluids and probably exercise at a reduced intensity or not at all. Donating blood markedly reduces competitive performance for three to four weeks as it takes that long for blood hemoglobin levels to return to normal.
You should not donate blood more often than every eight weeks because it takes that long to replace lost nutrients. If you donate blood frequently, you need to make sure to replace the B vitamins and possibly the iron that you lose with the blood. You can meet your needs for iron by eating meat, fish or chicken or by taking iron supplements; and you can meet your needs for the B vitamins with whole grains and diary products. Donating blood at least four times a year may help to prevent heart attacks by lowering blood cholesterol levels significantly and reducing iron levels. Iron in the bloodstream converts LDL cholesterol to oxidized LDL which forms plaques in arteries.