Iron supplementation for restless legs syndrome is recommended when ferritin is below which value?

• A. 75 ng/mL
• B. 150 ng/mL
• C. 30 ng/mL
• D. 100 ng/mL

Answer: (A)

Iron status drives symptoms in restless legs syndrome because CNS iron is essential for dopamine pathways, and ferritin reflects the body's iron stores. When ferritin falls to a level that signals depleted iron stores, supplementing iron can improve RLS symptoms. Evidence supports starting iron therapy when ferritin is below about 75 ng/mL, as this threshold balances benefit with safety, and IV iron is commonly used in this range. If ferritin is higher than this, iron therapy is less likely to help and isn’t routinely started. The other ferritin levels listed are either typical markers for general iron deficiency (lower values) or higher thresholds not used to trigger treatment for RLS. Thus, 75 ng/mL is the appropriate cut-off.