Institutional guidelines advise holding hydroxyurea if any of the following: absolute neutrophil count <1250/µL; platelet count <80K/µL; reticulocyte count <100K/µL, unless hemoglobin >8.0 gm/dL.

When do you hold hydrea?

If neutropenia (ANC <1300/μL) or thrombocytopenia occurs, hold hydroxyurea and repeat CBC with differential in 2 weeks. If toxicity is associated with illness and subsequently resolves, hydroxyurea should be restarted at previous dose and dose escalation may continue.

What should I monitor with hydroxyurea?

Once a stable dose is established, laboratory safety monitoring should include CBC with WBC differential, reticulocyte count, and platelet count every 2–3 months. Patients should be reminded that the effectiveness of hydroxyurea depends on their adherence to daily dosing.