Dear friend, welcome and thanks for entrusting your query here at Healthcaremagic! I am Dr. Prasad Akole (Critical Care Expert- http://bit.ly/Dr-Prasad-Akole) and am glad to address to your query here. She is already on high dosages and three drugs. She has to be evaluated for any causes of resistant high sugars. She is compliant with drugs? Are there any infection, stress, complications, medicines like steroids going on? Is there resistance suspected? Complications such as HONK, DKA, ketosis should be looked at. May have a scope of increasing metformin, if evaluation permits. Different combinations can be tried. Ask your doctor about this and sometimes insulin is needed. He is the best person to guide you as sugar management depends on various factors considered together. I hope to have answered your query satisfactorily. I would be glad to answer any further queries. Please ask for any clarifications before closing and rating this answer. Take care and please keep me informed of your progress at Good Luck! Thank you!!