Haemoglobin (Hb) is a specialised protein in red blood cells that carries oxygen to the tissues and returns carbon dioxide from tissues to the lungs. Iron is essential for the manufacture of haemoglobin. 

Prior to each blood donation, you will be tested for your Hb level usually through a simple finger-prick test at the blood donation site. Donors must have a Hb level of at least 12.5g/dl for females and 13.0g/dl for males before they can donate blood. This is to ensure the safety of the donor as frequent blood donations without sufficient replacement of the iron can lead to iron deficiency anaemia.