I got my initial diagnosis of lupus from having been sent to a hematologist for blood issues. Lupus is an opportunistic disease, and where ever you have a weekness in your body, there it'll be... If you're losing red blood cells & hemoglobulin (hemoglobulin is a protein, part of the red blood cell), that's what carries the oxygen to your muscles, and is probably a contributing factor to the way your arms & legs feel, along with the dizziness and fatigue. You might also ask if they want to do a breathing function test on you. If you smoke, quit now. I don't know how "common" it is for lupus to attack the blood, versus say how "common" it is for it to attack the kidneys, but it does attack the blood of some of us. Blood vessels on others, etc.
"There but for the grace of God, go I."
"... His mercy endureth for ever."