A Study of Oral L-citrulline in Sickle Cell Disease

Inclusion Criteria: 1. Sickle cell disease genotypes (HbSS, HbS/β-thalassemia 2. HbS/β+thalassemia, HbSC) 3. Patients with sickle cell disease aged 10 to 25 years old 4. Patients ages 10 through 17 years of age, whose parents have signed permission, and who provide signed patient assent themselves 5. Patients 18 through 25 years of age who provide signed consent. Exclusion Criteria: 1. Presence of any acute illness defined by fever \>100.4°F within the past 48 hours 2. Presence of sickle cell pain crisis defined by the presence of pain requiring oral or parental opioid therapy. 3. Presence of acute chest syndrome or presence of any other complication related to sickle cell disease requiring hospitalization such as splenic sequestration, hepatic sequestration, stroke, avascular necrosis of the hip/shoulder, acute priapism, and patients with diabetes etc. 4. Severe anemia (hemoglobin \< 5g/dL) 5. History of red blood cell transfusion within the last 14 days 6. Systemic steroid therapy within the last 48 hours 7. Pregnant (as confirmed by a negative urine pregnancy test) or lactating female 8. Alanine/aspartate transferase \>2x upper limit of normal laboratory range for age. 9. Elevated serum creatinine: Age 6 to 13 years \> 0.9 mg/dL, Age 14-17 years 1.0 mg/dL, Age \>18 years \>1.5mg/dL 10. Patients with an inability to give assent (ages 10 to 17 years) or consent (ages 18 through 25 years) will be excluded 11. History of diabetes due to risk of electrolyte imbalance