As is well known, there are two types of Shabbat prohibitions: Torah prohibitions and rabbinic prohibitions (the latter type is also called shvut). There is a principle that one desecrates Shabbat and performs even melakhot prohibited by Torah law on behalf of a gravely ill person, someone whose life is in danger. In contrast, when caring for someone who is ill but whose life is not in danger, one may not violate Torah prohibitions. However, the Sages permitted the violation of prohibitions that they themselves enacted to treat someone who is sick.
One who is bedridden due to his illness is considered a regular sick person. Even if, for some reason, he is not actually lying down, he is considered sick as long as this is the type of illness that generally causes people to lie down. Similarly, if one is suffering from pain that weakens his entire body (for example, a migraine), he is considered a sick person, even if he has not actually gone to lie down (SA 328:17). Furthermore, even if one is walking around and looks well, if it is clear that without a particular treatment he will need to lie down, one may transgress rabbinic prohibitions to prevent this from happening (SSK 33:1). If a child needs something very badly, he is considered a sick person, even if he has not gone to lie down (Rema 328:17; MB 276:6; above 24:6).
The easiest and most accepted way of taking care of a sick person is with the help of a non-Jew. As we have seen (above 25:1), under normal circumstances the Sages prohibited asking a non-Jew to undertake melakha on behalf of a Jew on Shabbat, but they permitted doing so for the sake of a sick person (Shabbat 129a). Therefore, one may ask a non-Jew to turn a light on or off for a sick person, to turn a heater on for him, to cook food for him, to travel in order to bring him medication, to press elevator buttons for him, and to administer X-rays for him. Similarly, one may ask a non-Jewish dentist to treat a patient whose toothache is causing him pain that extends throughout his body. One may ask a non-Jewish doctor to write a prescription for a sick person. One may ask a non-Jew to drive a sick person to the doctor or to the hospital. In such a case, a Jew may accompany the patient, on condition that neither he nor the sick person performs any melakha themselves.
A regular sick person may take whatever medications he needs, since the rabbinic prohibition against taking medicine applies only to a mildly sick person (Rema 328:37; see BHL ad loc.).
If no non-Jew is available, according to Ran, a Jew may not transgress rabbinic prohibitions for a sick person. According to Rashba, however, he may, and we follow this position in practice. However, le-khatĥila, if possible, it is still preferable to arrange for a non-Jew to do whatever is necessary, or for a Jew to use a shinui, so that the prohibition will be reduced to a shvut di-shvut (above, 9:11). If there is no choice, and the sick person desperately needs care, a Jew may do rabbinically prohibited melakhot on his behalf. For example, if he needs a light turned on or off, one should do this with a shinui such as using one’s arm or leg, so that the prohibition is only rabbinic (above, 9:3). Similarly, if the sick person needs a heater or air conditioner turned on or off, one may do this with a shinui.
All agree that one may not turn off a light so a sick person can sleep (Shabbat 30a). At first glance, since this is a melakha she-eina tzerikha le-gufah, which according to many poskim is only rabbinically prohibited (above, 9:6), Rashba and those who follow him should permit it for a sick person even without a shinui. Nevertheless, since turning off the light is more severe than other rabbinic prohibitions, the Sages forbade doing it even for a sick person (MB 278:3). Turning off a light to allow a sick person to sleep is permitted if one does so with a shinui, for example by using his arm.
Eating rabbinically prohibited food is more severe than transgressing a shvut, and a regular sick person thus may not do this (Rema, YD 155:3). However, he may eat food that was cooked by a non-Jew (SA 328:19), and he should make the regular berakhot over the food (MB ad loc. 63). One may move a muktzeh item for a sick person without using a shinui. Some are stringent and maintain that le-khatĥila one should still use a shinui (MB 328:58). Some argue that the enactment against taking medicine (out of concern that people will end up grinding ingredients) applies to a regular sick person. (See BHL 328:37, s.v. “ve-khen.”) However, in practice, we rule that the enactment applies only to a mildly sick person or to one experiencing discomfort, as described in the next section (Beit Yosef and Rema 328:37).