After donating blood, a patient may experience symptoms such as lightheadedness, residual bleeding at the puncture site, bruising or arm pain. However, the donation procedure itself is considered safe. Patients can stave off the after-effects of blood donation by drinking extra fluids and avoiding strenuous physical activity, according to WebMD.
Typically, donors remain under observation for 15 minutes and eat a snack before their release from the blood donor center. Healthy adults are generally able to donate a pint of blood without risk to their health. The body replaces lost fluids within 24 hours, and red blood cells are replenished over a period of weeks.