If one is suffering from constipation on Shabbos, can one take a suppository?
Answer:
It is forbidden to take medicine or use suppositories to aid a condition of constipation on Shabbos, unless this causes suffering to the degree that the person is unable to function.
Sources:
See Mishnah Berurah, 328:118, 140; Shulchan Aruch 328:49 and Mishnah Berurah 150; Shemiras Shabbos Kehilchasah Chap. 24 no. 11, and Chap. 33 no. 12.