Hi, I take sitagliptin but not T1,
What the drug does is stimulate your pancreas to create more insulin for the initial digestion stage. It is obviously more complicated than that. Because it changes the chemical reaction.
But I have never heard of T1s getting prescribed it.
Yes, if your pancreas does not produce any insulin at all, then this tablet isn't any use. It may work if you do produce some of your own insulin, but can in some people wear out the remaining insulin producing cells a bit quicker.
Why has your doctor prescribed it rather than change your injected insulin requirements?