Ferritin level 301, platelets 74, vit d 13 ng/ml hemoglobin is 14.2 good. b12 is bit on the low side at 354 but ok. gastric bypass in 2003. lupus?

Why do you ask?: With a serum ferritin twice the upper limit of most reference ranges for a young woman, you have hemochromatosis / iron overload until proved otherwise. If it's getting advanced, this could explain your thrombocytopenia, though lupus is also in the "diff". You may have both ;/or something else. Your platelets should perhaps be checked for surface antibodies as part of a full workup.

Lupus: What makes you think it is lupus? Did you have a blood test for anti-nuclear antibodies or any other autoimmune workup? Or do you have any symptoms? If you have concerns, go see a rheumatologist.