Mean Corpuscular Volume

Mean corpuscular volume measures the average size of your red blood cells, expressed in femtolitres, an almost unimaginably tiny unit of volume. While the number itself may seem abstract, the size of your red blood cells can reveal a surprising amount about your nutritional status and overall health. Red blood cell size matters because cells that are too large or too small may not function as efficiently as they should. Ideally, your red blood cells are just the right size to carry a full load of haemoglobin, squeeze through the smallest capillaries, and release oxygen where it is needed. When the average size shifts significantly in either direction, it often points to an underlying nutritional shortfall or other factor worth investigating.

Your bone marrow produces millions of red blood cells every second, and during their development these cells go through several stages of growth and division. Adequate supplies of iron, vitamin B12, and folate are all essential for this process to run smoothly. When B12 or folate is in short supply, the cells may not divide properly and end up larger than usual. When iron is lacking, the cells tend to be smaller because there is not enough raw material to build them to full size. Think of it like baking, if you run short of a key ingredient, the finished product comes out a different size than intended.

Dietary habits, alcohol consumption, certain medications, and absorption issues can all influence your MCV. It is also worth noting that MCV naturally tends to be slightly higher in older adults. Because changes in red blood cell size often develop gradually, they can be easy to miss without a blood test. If your MCV is outside the typical range, your GP can look at it alongside your other results to work out the most likely explanation and suggest any appropriate next steps.