The goal of this short term prospective Phase II study is to compare the effects of two alternate daily doses of zinc (25 and 40 mg/day) in 34 randomly assigned homozygous Sickle Cell Disease (SCD-SS) patients aged 15-40 years old. The main question it aims to answer is: Which biomarkers are most responsive to zinc supplementation, and what is the maximum tolerated zinc dose that induces the desired changes in biomarkers of bone turnover? Participants will be recruited from 6 American Society Hematology Research Collaborative SCD Centers. Eligible SCD subjects will be invited to participate in the 16-week study, involving 2 baseline blood draws 4 weeks apart, followed by a 12-week zinc intervention. The findings from this study will be used to determine the dosage of zinc to be used in a larger, future study on the long term impact of zinc supplementation on bone health in SCD-SS.