Hemoglobin subunits - sometimes displayed simply as "Hemoglobin".
Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. Hemoglobin is made up of four protein molecules (globulin chains) that are connected together. The hemoglobin test is often used to check for anemia, usually along with a hematocrit or as part of a complete blood count (CBC).
The wrong molar concentration reference values in the literature may arise from the method by which the concentration is measured: automatic analyzer measure absorption of (chemically modified) hem groups and also make the final calculation with chemical properties (e.g., absorption coefficients) of the hem groups, leading to the wrong 4-fold higher molar concentration range.
The molar hemoglobin concentration given in SI units therefore has to be in a range between about 2 and 3 mmol/l.
Wrong molar hemoglobin reference values—a longstanding error that should be corrected