Rh disease, one of the causes of hemolytic disease of the newborn
Transfusion reaction to blood transfusions
Mechanical trauma to red blood cells
Microangiopathic hemolytic anemias, including thrombotic thrombocytopenic purpura and disseminated intravascular coagulation
Infections, including malaria
Heart surgery
Haemodialysis
Parasitic
Trypanosoma congolense alters the surfaces of RBCs of its host and this may explain T. c. induced anemia

Blood loss
Anemia of prematurity, from frequent blood sampling for laboratory testing, combined with insufficient RBC production
Trauma or surgery, causing acute blood loss
Gastrointestinal tract lesions, causing either acute bleeds (e.g. variceal lesions, peptic ulcers) or chronic blood loss (e.g. angiodysplasia)
Gynecologic disturbances, also generally causing chronic blood loss
From menstruation, mostly among young women or older women who have fibroids
Many type of cancers, including colorectal cancer and cancer of the urinary bladder, may cause acute or chronic blood loss, especially at advanced stages
Infection by intestinal nematodes feeding on blood, such as hookworms and the whipworm Trichuris trichiura 
Iatrogenic anemia, blood loss from repeated blood draws and medical procedures.The roots of the words anemia and ischemia both refer to the basic idea of "lack of blood", but anemia and ischemia are not the same thing in modern medical terminology. The word anemia used alone implies widespread effects from blood that either is too scarce (e.g., blood loss) or is dysfunctional in its oxygen-supplying ability (due to whatever type of hemoglobin or erythrocyte problem). In contrast, the word ischemia refers solely to the lack of blood (poor perfusion). Thus ischemia in a body part can cause localized anemic effects within those tissues.
Causes
The causes of anemia may be classified as impaired red blood cell (RBC) production, increased RBC destruction (hemolytic anemia), blood loss and fluid overload (hypervolemia). Several of these may interplay to cause anemia. The most common cause of anemia is blood loss, but this usually does not cause any lasting symptoms unless a relatively impaired RBC production develops, in turn, most commonly by iron deficiency. Impaired production
Disturbance of proliferation and differentiation of stem cells
Pure red cell aplasia
Aplastic anemia affects all kinds of blood cells. Fanconi anemia is a hereditary disorder or defect featuring aplastic anemia and various other abnormalities. Anemia of kidney failure due to insufficient production of the hormone erythropoietin
Anemia of endocrine disease
Disturbance of proliferation and maturation of erythroblasts
Pernicious anemia is a form of megaloblastic anemia due to vitamin B12 deficiency dependent on impaired absorption of vitamin B12. Lack of dietary B12 causes non-pernicious megaloblastic anemia. Anemia of folate deficiency, as with vitamin B12, causes megaloblastic anemia
Anemia of prematurity, by diminished erythropoietin response to declining hematocrit levels, combined with blood loss from laboratory testing, generally occurs in premature infants at two to six weeks of age. Iron deficiency anemia, resulting in deficient heme synthesis
Thalassemias, causing deficient globin synthesis
Congenital dyserythropoietic anemias, causing ineffective erythropoiesis
Anemia of kidney failure (also causing stem cell dysfunction)
Other mechanisms of impaired RBC production
Myelophthisic anemia or myelophthisis is a severe type of anemia resulting from the replacement of bone marrow by other materials, such as malignant tumors, fibrosis, or granulomas.