Blood is one of the most important connective tissues in human. As of today, there is no innovation made on manufacturing blood cells, hence blood donors are the only hope. Blood is the most valuable gift you can give since it is a gift of life. Studies show that one blood donation can save three lives. In return blood, donors have a lot of benefits.
You are eligible to donate blood if you weigh more than 50 kg and are above 17 years old.

Merits :
Blood donation is proven to have emotional and physical benefits

Helps in reducing stress.
Improves emotional well-being.
Lowers the risk of heart disease and heart attack by reducing blood viscosity
Prevents certain types of cancer.
Cut down the risk of hemochromatosis which is caused due to a high level of iron store in the body.
Proven to reduce the danger of damaged liver and pancreas.
Helps in reducing blood pressure.

Overall blood donation hinders obesity by burning excessive calories and helps in replenishing blood. It improves your cardiovascular health. One can donate blood for a maximum of 24 times a year. Also, there are a number of tests you need to go through before blood donation, which can help in early diagnosis of certain disease.

Demerits :
Blood donation does not have any serious side effects on a healthy adult. One can donate put to one pint of blood, which is recuperated with 24 to 72 hours. However, there can be minor side effects such as :

Pain and bruises caused due to the needle.
Dizziness and nausea.
Weakness.
Fainting.
Continued bleeding.
Lightheadedness.

One can take 6 to 8 weeks to recover from a blood donation. It is quite a time-consuming process. It is advised to avoid any intense physical activities after blood donation. Importantly, you need to make sure the needle is clean and sterilized to avoid infections.

Who should avoid blood donation:
A person who suffers from diabetes
Any person who is infected by a flu
A person who is diagnosed with AIDs
Pregnant women are advised to avoid blood donation
A person suffering from high or low cholesterol levels are not eligible to donate blood
If a person is on certain antibiotics they are not allowed to donate blood
A person suffering with any kind of disease that spreads through the exchange of blood fluid is not allowed to donate blood.

Author's Bio: 

Athreya Ayurvedic Integrative Health Centre (AAIHC) - Come and experience natural healing sciences in action geared for regaining your vibrant health and longevity by NAMA registered practitioners.
At our centre, appropriate health modalities such as Ayurveda, Acupuncture, Yoga therapy and Massage therapy are chosen for the most effective health outcomes. Integrative care focuses on a "patient-centred approach" by using the best possible evidence-based traditional health systems. For your health needs, we tailor personalized protocols for achieving optimal health.