Hi, Chythar! Great to see your phosphors! And how wonderful you found the right treatment for your RLS!

You're absolutely right -- low iron is one of the factors in RLS. The lab test is ferritin, which is a transfer-form of iron (as opposed to hemoglobin, which is the form in red blood cells, and hence "out of circulation"). In my case, given my age, diet, and history of having RBC iron levels consistently near the high end of normal, it's unlikely.