Which of the following codes should you use for anemia when the underlying condition is known?

The appropriate choice for coding anemia when the underlying condition is known is found in the range D63.1. This code specifically refers to "Anemia in chronic disease," highlighting that the anemia is a secondary condition to an underlying health issue rather than a primary diagnosis.

Using D63.1 allows healthcare providers to accurately document and convey the clinical picture of a patient who is dealing with both anemia and an underlying condition, ensuring the information is clear for treatment planning, billing, and epidemiological tracking.

The other options reflect different categories of conditions and do not pertain directly to anemia when the underlying cause has already been identified. For example, the codes starting with F (which are primarily used for psychological disorders) and those in the C and D range that cover other groups of diseases or conditions are not suitable for this specific situation. Thus, D63.1 is the most clinically relevant and precise choice for this scenario.