Anemia of Chronic Disease (ACD): This is often the most common cause of normocytic anemia, especially when ferritin, B12, and liver function tests are normal. ACD can occur in the context of chronic infections, chronic immune activation, or malignancy, leading to a decrease in erythropoietin production or response.

Acute Blood Loss: Although the patient may not have visible signs of bleeding, occult blood loss can lead to normocytic anemia. The normal ferritin level might not have had time to decrease in the case of recent blood loss.
Hemolysis: Normocytic anemia can be a feature of hemolytic anemias, where red blood cells are destroyed faster than they can be made. Normal liver function and ferritin do not rule out hemolysis, as these tests can be normal in certain types of hemolytic anemia.
Chronic Kidney Disease (CKD): CKD can lead to normocytic anemia due to decreased erythropoietin production by the kidneys. Early stages of CKD might not significantly alter liver function tests or ferritin levels.

Paroxysmal Nocturnal Hemoglobinuria (PNH): A rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells, bone marrow failure, and the potential for thrombotic events. It's crucial to consider PNH due to its severe consequences if left untreated.
Myelodysplastic Syndromes (MDS): These are a group of disorders caused by poorly formed or dysfunctional blood cells, often presenting with normocytic anemia. MDS can progress to acute myeloid leukemia, making early diagnosis critical.

Pure Red Cell Aplasia: A rare disorder where the bone marrow fails to produce red blood cells, leading to severe anemia. It can be congenital or acquired, often associated with autoimmune diseases, lymphoproliferative disorders, or certain medications.
Diamond-Blackfan Anemia: A congenital condition characterized by a failure of the bone marrow to produce red blood cells, typically presenting in childhood but can be diagnosed later in life if mild.