Is It Safe To Take Metformin Inspite Of Taking Januvia For Diabetes?

Hi, my doc. Suggested Onglyza as Metformin HCL ER 750 was not controlling my diabetes and I was fed up with the diarrhea I had had for yrs. but he had no samples for me and anyway my part d drug company denied his request....so he gave me Januvia samples.....no diarrhea for the past week has been heavenly....but the Januvia samples. Are not keeping my levels down either. I have had diabetes for about 20 yrs but six yrs ago was diagnosed wt Pulmonary Fibrosis....2 yrs later I had an attack, was treated wt Prednisone and antibiotic in case I also had pneumonia....I seemed to do well for a couple of yrs but then had a surgery that resulted in a blood clot in lung...this left me in bad shape and Denver. Jewish doc again put me on prednisone and then new drug Esbriet...slows the progression of if....I have been thru wt the prednisone for two months and on the esbriet for 3 months. Now if the Januvia isn t keeping my sugar down and Part D company won t let me try Onglyza and I can t tak metformin.....wot now??? I left msge for primary doc but as usual no answer yet!!! Part D company told me to ask about Tradjenta.....would this be a good choice if Januvia isn t available in higher dosage than 100mgs????