Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Do not wait for a routine appointment if the child develops severe breathing difficulty, fainting, chest pain, confusion, vomiting blood, or significant ongoing bleeding.
Follow-up testing confirms whether treatment is working.
Timing depends on the child's age, symptoms, anemia severity, and treatment plan.
A clinician may repeat the CBC and later check ferritin or other iron tests.
Follow-up should also address the underlying risk through dietary changes, management of heavy periods, treatment of digestive disease, or dietitian support.
The article also says
Hemoglobin may improve before iron stores are replenished.
Treatment therefore often continues after hemoglobin returns to the expected range, but the clinician should determine the duration.
If results do not improve, the healthcare team may check how the medicine is measured and given, whether doses are missed, and whether side effects interfere with treatment.
Further assessment may look for continued bleeding, poor absorption, inflammation, lead exposure, or another type of anemia.
Every sign above is quoted from the sofidex article on Anemia caused by low iron - children. If you are not sure, err upward — it is always reasonable to be checked.