Heartburn Medication on Shabbos
Under halacha, there are many categorizations of a sick person, which have many implications on what a person can do to heal himself. One must perform any malacha necessary to heal a Choleh SheYesh Bo Sakanah (A sick person in mortal danger). If one is a Choleh Shein Bo Sakanah (An ill person who is bedridden), one may give medication to such a patient. Then there is a Maichush, one with a minor ailment that causes mild discomfort but can still function. (Shulchan Aruch 328). Regarding heartburn, since it is considered a minor ailment, one would not be permitted to take pharmaceutical medications that reduce the production of gastric acid (e.g., proton pump inhibitors). However, Rav Asher Weiss ruled that if one cannot fall asleep at night and it causes significant pain, then one may be permitted to take medication.
Regarding chronic heartburn caused by peptic ulcer disease or a weakened lower esophageal sphincter that requires ongoing therapy, one may take medication if it is taken regularly. (Shemiras Shabbos Kehilchasa 34:4)
Foods known to alleviate heartburn may be consumed on Shabbos as they are not considered medication. However, a flavored medication that tastes like candy is not permissible to use to alleviate heartburn since it is only taken by those who feel sick. Additionally, a concoction of baking soda and water or other homemade remedies may not be used because they are not usually consumed by a person who is not sick.
However, if one prepares it before Shabbos, then one is permitted to use it. The reasoning is based on the Shulchan Aruch (328:21), which states that a person may apply Kilorin (collyrium) to his eyes on Shabbos, provided that the ingredients are soaked before Shabbos. This is permitted because it eliminates the risk of violating the prohibition against crushing medicinal herbs, which is the primary concern behind taking medications on Shabbos. When seen by others, the mixture does not resemble medication, preventing potential misunderstanding (Shemiras Shabbos Kehilchasa ibid. and Orchos Shabbos 2:20:144).
Adapted from medicalhalacha.org