Anemia

Anemia may mean two things:

• A decreased level of Hb (hemoglobin) in the blood, in absolute numbers. This may be because the level of Hb in the red blood cells is low, or because the level of red blood cells (which contain all the Hb in the blood) is low.
• A decreased capacity of each Hb molecule to bind oxygen, due to a deformity, or if too much of the iron in Hb is oxidized (from Fe²⁺ to Fe³⁺).

Low Hb level

There are multiple possible causes for a low Hb level.

• Low serum iron; if there is too little iron available, too little new Hb molecules are produced

Hemoglobin

Hemoglobin (Hb) is a iron-containing protein in the blood. Hb transports oxygen (and some other gasses, such as CO₂ and nitric oxide) to all your organs. Organs need oxygen to make use of nutrients (including energy) through oxidation. A lower level of Hb may therefore lead to a (relative) lack of oxygen in various organs.