Alcohol consumption: Mild macrocytosis can be seen in individuals who consume alcohol regularly, even without significant liver disease or anemia. Alcohol interferes with folate metabolism, potentially leading to macrocytosis despite normal folate levels.

Hypothyroidism: Thyroid disorders, particularly hypothyroidism, can cause macrocytosis. The mechanism is not fully understood but may relate to decreased metabolism and alterations in lipid metabolism affecting cell membrane structure.
Liver disease: Early or mild liver disease can cause macrocytosis due to impaired lipid metabolism and alterations in cholesterol and phospholipid synthesis, which are essential for cell membrane production.
Medications: Certain medications, such as anticonvulsants (e.g., phenytoin), can induce macrocytosis as a side effect, possibly through interference with folate metabolism or direct effects on bone marrow.

Myeloproliferative neoplasms (MPN): Although less common, MPNs like essential thrombocythemia or polycythemia vera can present with macrocytosis. These conditions have significant implications for morbidity and mortality if not diagnosed and managed properly.
Myelodysplastic syndromes (MDS): MDS can cause macrocytosis and may not always present with anemia or cytopenias early in the disease course. Missing this diagnosis could lead to delayed treatment and poor outcomes.

Ornithine transcarbamylase deficiency: A rare genetic disorder affecting the urea cycle, which can lead to hyperammonemia and macrocytosis due to the toxic effects of ammonia on the bone marrow.
Copper deficiency: Although more commonly associated with microcytic anemia, copper deficiency can rarely cause macrocytosis, possibly through its role in maintaining normal hematopoiesis and connective tissue health.
Zinc deficiency: Similar to copper, zinc plays a crucial role in numerous enzymatic processes, including those involved in hematopoiesis. A deficiency could potentially lead to macrocytosis, although this is less well-documented.