It would certainly seem that giving / donating blood could be beneficial to your health as well as to the health of others. This isn't the reason the majority of people who visit their blood bank or similar donate, with the usual motivation being to give a little back and to do their bit. That said it does seem that as well as your blood donation helping as many as three people in need it can also benefit your own health.
Donating blood will actually increase your calorie burning rate in the short term. A pint donated could burn as much as 650ml calories which is significant if not a long term weight loss benefit. If you needed extra motivation to give blood a good week on the scales that week could be it.
Before you can give blood and before your blood can be used you receive a non-evasive check up to ensure you are in good health and that your blood is "clean and clear" from infectious diseases (HIV, syphilis,hepatitis B and C and more). Your blood pressure is also checked, alongside your hemoglobin level.
Obviously if you have any reason to be concerned about your health you should see your GP but this check up is a bonus which allows you to monitor your health while helping others.
Better Blood Movement
There are a number of things which negatively impact your health related to blood for example stress, exposure to harmful chemicals and pollutants in the air, a poor diet and more. Any and all of these tend to thicken your blood (making ithypercoagulable) which in turn can increase your risk of heart disease, stroke, diabetes (Type 2), blood clots and more.
Giving blood actually improves blood flow, lowers the viscosity level of your blood and overall improves circulation which is turn reduces the risks hypercoagulable blood contributes to.
Balancing Out Your Iron Levels
Anemia, fatigue and a poor immune system are all side effects or caused by having a low iron level. Clearly low iron is not good and yet too high a level is more common that you would suppose and may also cause a number of different health issues relating mostly to your cardiovascular system.
Some research (documented by the American Medical Association) shows that those who donate blood regularly (every six months or so) were considered to have a low risk of cardiovascular problems and by association be at a lower risk of heart attack and stroke. If that isn't a reason to help out by donating blood I don't know what is!
If you are a regular blood giver, well done you! If not, just think about the good you could do for others as well as the benefits to yourself if you were eligible to donate.
You can learn more about donating blood on the NHS Blood Donation website.