Donating blood is a generous life-saving gift which is tolerated very well by most donors. But some donors, especially teen donors, may experience side effects from donating blood. Most effects are minor but less than 1 percent of blood donors may experience more severe side effects.
Only 1.2 percent of 5,000 donors experienced a reaction from blood donation, according to Doctors Antonio Crocco and Domenico D’Elia in their article, "Adverse reactions during voluntary donation of blood and/or blood components. A statistical-epidemiological study" published in the July 2007 journal Blood Transfusion. Of the 1 percent of donors who experienced a negative reaction, the vast majority of reactions they had were classified as minor. Minor side effects were typically localized skin effects from improper insertion of the needle. If the needle is inserted so that it slips through the vein, it can cause local bleeding under the skin resulting in a bruise (also called a hematoma). Usually, a hematoma will slowly resolve over a few days, as the pooled blood breaks down and is removed from the area.
Other mild reactions described by Doctors Crocco and D’Elia included systemic reactions reported by donors including feelings of agitation or concern about donation. Some donors experienced other systemic side effects such a sweating, becoming pale, feeling cold, weak or nauseous. Usually, these symptoms subsided soon after donation. Rarely, these systemic systems progressed to feeling light-headed. According to the American Red Cross, feeling faint is a minor side effect which generally passes in a few minutes after donation. Infrequently, these pre-fainting symptoms can progress to actual loss of consciousness.
In their study, Doctors Crococ and D'Elia reported that only four blood donors out of nearly 5,000 studied had side effects classified as severe. These four donors experienced reactions including vomiting, losing consciousness temporarily due to low oxygen levels to the brain and brief muscle spasms.
Indirect injuries from losing consciousness and falling caused more serious physical harm than the actual donation, according to Dr. Anne F. Eder and colleagues who reported an increased risk of fainting in teen donors compared to older donors in their article "Adverse Reactions to Allogeneic Whole Blood Donation by 16- and 17-Year-Olds" reported in the May 21, 2008 issue of the Journal of the American Medical Association. Their study analyzed over 150,000 donations by teenagers across nine American Red Cross Donation Centers. Teen donations account for between 4 and 11 percent of all American Red Cross donations. About four donors per 100 had side effects, but 10 percent of these side effects were experienced in the 16 and 17 year olds, compared to only 3 percent in donors aged 20 or older. The study could not explain this age-related difference in experiencing side effects from blood donation.