If MCV is greater than 100, which vitamin levels should be checked first?

When the mean corpuscular volume (MCV) is greater than 100 fL, this indicates macrocytic anemia. The most common causes of macrocytic anemia are deficiencies in vitamin B12 and folate. Therefore, it is essential to check the levels of these vitamins when faced with elevated MCV values.

Vitamin B12 is crucial for DNA synthesis and red blood cell formation, while folate (vitamin B9) also plays a vital role in these processes. A deficiency in either of these vitamins can lead to the production of abnormally large red blood cells, which directly contributes to an increased MCV reading.

Checking iron and ferritin levels may be relevant in other types of anemias, particularly microcytic anemia associated with iron deficiency. However, it is not the first step when macrocytic anemia is suspected. Similarly, calcium and vitamin D, as well as zinc and copper, are not directly linked to the macrocytic changes observed with elevated MCV.

By prioritizing the assessment of vitamin B12 and folate in the context of macrocytic anemia, appropriate and timely diagnosis can be achieved, allowing for correct management of the underlying deficiency.