Can weight gain from prednisone (20lbs) cause an increase in creatinine and bun? have had increasing labs past 3 months. been on pred 6mo. almost off

Unlikely: Prednisone may cause a negative nitrogen balance due to protein catabolism and, therefore, may cause a rise in bun. It may also cause sodium and fluid retention and potassium loss. However, I am unaware of any effects of corticosteroids on serum creatinine or glomerular filtration rate per se. If you do have sle, it is possible that you may have renal involvement.