Interrupting Prayer - Should I Continue from Where I Stopped or Start Over?

To the inquirer,

After beginning the Amidah (also known as the Shmonah Esrei), one should not interrupt to go to the bathroom, except if one can sufficiently control oneself, then one completes the prayer. [This is, of course, assuming that before the prayer one checked themselves and did not feel any need at all, even regarding what could arise within the next 72 minutes (and if one did feel the need before praying, one should not have begun to pray; and if one did begin and had to interrupt, they return to pray from the beginning afterwards)].

If [in a situation where one checked themselves beforehand suddenly finds that they] cannot control themselves and must interrupt, if the time taken in the interruption until one resumes praying is longer than the time it usually takes to recite the entire Amidah from beginning to end, one starts over from the beginning.

If less time has passed, there is uncertainty according to the Mishnah Berurah; and it seems that the consensus favors returning to the point where one stopped (see Biur Halacha, Orach Chaim 92:14).

Best wishes,

Rabbi Nachum