What is MCHC?

A red cell of the usual size may still hold less haemoglobin than it should. Only a concentration shows that, which is what MCHC adds to the other red cell measures.

MCV gives the size of a red cell and MCH the amount of haemoglobin inside it, so with MCHC the three say whether cells are small, sparsely filled, or both at once. Haemoglobin gives the total in a volume of blood, and Ferritin the iron stores that set how much of it the bone marrow could put into each cell.

When iron runs short the marrow fills cells less densely than usual. Inherited differences in the red cell membrane, or in haemoglobin itself, change how densely a cell can be packed whatever the iron supply. MCHC is worked out from Haemoglobin and Haematocrit, the share of volume the cells occupy, so a sample stored too long or misread by the machine moves MCHC while the blood itself is unchanged.

A red cell is filled once, with whatever iron the marrow has at the moment it builds the cell, and holds that for about 120 days. MCHC therefore moves over months. Readings a year apart describe two entirely separate populations of cells, so a difference between them means the marrow was filling cells differently. This is Do Health's monitoring schedule, not a general recommendation for everyone.