Medical Halacha – Fasting on Yom Kippur


Rabbi Yehuda Finchas

Ralph suffers from kidney complications and his wife Sandra is currently pregnant with a high-risk pregnancy. They were each horrified to hear from their respective physicians they must each drink two litres of water every single day, including on Yom Kippur. They have never broken their fast before and asked me if they should fast or at least use IV for hydration instead of actually drinking. 

When Your Medical Advisor Prohibits Fasting 

The Shulhan Aruch (O.C. 818:1) is clear: If a qualified medical practitioner establishes that fasting could potentially endanger a person’s life, he or she must not fast, as it is forbidden to place one’s life in danger. Fasting when medically advised to not do so is considered a grave sin, as the Torah instructs us to “live by them” (Vayikra 18:5) meaning that mitzva observance must not be the cause of a person’s death, including the mitzva to fast on Yom Kippur.  

If a person endangers his life by fasting it is considered an act of self-harm and falls under the prohibition of possible suicide. Hacham Ovadia (Yechaveh Daat 1:61) writes: “If there is concern of possible danger to his life by fasting, one must listen to the doctor and eat on Yom Kippur, because pikuach nefesh overrides the mitzva of fasting on Yom Kippur. If the sick person is stringent and fasts nonetheless, has he not acted in a pious manner; on the contrary, he will be punished for this.” 

According to the Shulhan Aruch (817:1), healthy pregnant women are generally able to fast on Yom Kippur and should do so, making sure to eat and drink sufficiently before the fast. The vast majority of poskim agree there is no blanket rule that exempts pregnant women from fasting; each case should be evaluated individually (Nishmat Avraham 617:1). If a doctor believes that a particular pregnant woman cannot fast due to a medical condition, or has a high- risk pregnancy, or is bleeding, or is experiencing contractions, she must not fast (Ohr Lezion 4:14:1). At the same time, she should find out how much liquid she needs to drink to remain safe and healthy and, if drinking will not suffice, how much she needs to eat.  

Drinking Shiurim – Small Amounts 

Similarly, if a doctor determines that fasting may cause a woman to miscarry, or she has experienced two or more miscarriages while fasting, she should drink shiurim (Hazon Ovadia, Yamim Norayim, p. 295). 

Drinking shiurim means drinking less than the measure of liquid for which a person is liable to receive the punishment of karet for consuming on Yom Kippur – a “melo lugmav”- a cheek-full (not a mouthful). While it is still prohibited, drinking this smaller amount does not carry the same severity of punishment. Therefore, when necessary and appropriate, there are instances where the poskim suggest drinking less than a shiur at a time instead of drinking normally. 

This quantity will vary from person to person. For an average person it is approximately 1.3 oz.; some plastic lechayimcups hold precisely this shiur. Alternatively, one can use a baby bottle (or the like) to measure the correct volume.  

To be considered as eating “less than a shiur” one needs to pause for a short period between consuming each volume of liquid. There is a difference of opinion as to the length of the interval necessary between drinking each shiur. Some say that it should be nine minutes; others say six, four, or two minutes. Others hold that “kedey shetiyat revi’it” – the time it takes to drink a revi’it, which is not more than four or five seconds – is enough of an interval (see, Yabia Omer, OC, 2:31). When advised to drink shiurim, a person should drink less than 1.3 oz. at a time, at an interval of at least five seconds is sufficient according to Hacham Ovadia, or up to nine minutes, only if this will not compromise their health. 

To answer Ralph’s and Sandra’s question, when permitted to drink on Yom Kippur, there is also no obligation to opt for artificial nutrition or hydration instead (Hazon Ovadia, p. 298, see, however, notes in Ohr Lezion 4:15:5).  

Some are fearful of eating or drinking on Yom Kippur due to the severity of the fast. However, they should be assured that the same Gd who commanded the healthy to fast, also commanded the seriously ill to eat. In fact, it is a mitzva for them to eat and no atonement is necessary.  

Rabbi Yehuda Finchas is a worldwide expert, lecturer, and writer on Medical Halacha, and is the head of the Torat Habayit Medical Halacha Institute. His latest book is entitled “Brain Death in Halacha and the Tower of Babel Syndrome.” To contact Rabbi Finchas or to receive a booklet on the Laws of Yom Kippur, email