My 13.5 year old dog has been slightly anemic for over a year... he used to have low blood platelets (2.5 years ago) and

Aloha! You're speaking to Dr. Michael Salkin
Bone marrow effective erythropoiesis (manufacture of red blood cells) is primarily judged by its release of reticulocytes - immature red blood cells without nuclei. Bone marrow function should respond normally in blood loss or hemolytic anemia, and reticulocyte production should be increased in proportion to the severity of the anemia. Anemia with appropriately increased erythropoiesis is classified as regenerative anemia. A nonregenerative anemia is indicated by finding clearly less than an expected reticulocyte response for the time after onset of an anemia and the severity of the anemia.

The 1.1 indicates that 1.1% of erythrocytes are reticulocytes and that's normal...but we don't want normal, we want to see a marked degree of stimulation (21-50%) - in other words ,we want to see that Ben can replace the red blood cells he's lacking. The percentage of reticulocytes can be misleading, however, because the percentage is a ratio of reticulocytes to mature RBCs. In anemia, the mature RBCs are variably reduced, thus the reticulocyte percentage overestimates the hematopoietic response. The absolute reticulocyte count is calculated by multiplying the reticulocyte percentage by the RBC count, so it adjusts the reticulocyte percentage for the severity of the anemia. Absolute reticulocyte count is the most consistent indicator of bone marrow production and is recommended as the best single indicator of regeneration in the dog.
41,800 is less than what's considered "no degree of regeneration" - 60,000. A marked degree of regeneration is >500,000.

Hence, Ben's anemia is nonregenerative - as seen with inflammatory diseases, chronic renal disease, chronic hepatic disease, hypothyroidism, hypoadrenocorticism, many bone marrow disorders - including malignancies, drug-induced hematologic dyscrasia, and various infections. His anemia is moderate - a normal HCT ranges between 35 and 52.

Please respond with further questions or concerns if you wish.