I have the flu. Must I fast on Tishe Beav?^[1]

A person who is sick [to the point of being bedridden^[2] even if it is not life threatening^[3]] and needs to eat, is not required to fast on Tisha B’av. Thus, if due to the flu you feel weak in your entire body, have fever, or are bedridden, then you may eat and drink as necessary.

How much may you eat and drink: Some Poskim^[4] rule that a sick person is only allowed to eat and drink in accordance to his medical need, to give him strength, but not any further. Thus, if one is medically required to drink but is not required to eat, then although he may drink, he is nevertheless to abstain from eating foods. The same applies to any sick person, that if he is able to suffice with drinking alone, then he is not to eat, and if he is able to suffice with one meal then he is not to eat any more. However, from other Poskim^[5] it is evident that a sick person is completely exempt from the fast.

[1] Michaber 554:6; Chayeh Adam 135:2; Kitzur SHU”A 124:7; M”B 554:11; Kaf Hachaim 554:33; Nitei Gavriel 65:12; See also: Rama 686:2 [regarding Taanis Esther]; Chayeh Adam 133:6; M”B 550:4; Kaf Hachaim 550:7

[2] As this is considered a Choleh Sheiyn Bo Sakana, mentioned in M”B 550:4; and so is implied also from Aruch Hashulchan 550:7; and Hagahos Rav Akiva Eiger 559:9; See however Aruch Hashulchan 554:7 that this applies even if he is not bedridden; See Nitei Gavriel 5:4 in name of Maharam Bent 550 that even if he is slightly ill one may be lenient

[3] See M”B 554:11; 550:4; Chayeh Adam 133:6; 135:2; Besamim Rosh 280; Yifei Laleiv 2:3; Kitzur SHU”A 124:7; M”B 554:11; Kaf Hachaim 554:33; Nitei Gavriel 65:12

[4] Chasam Sofer 157 “Is a sick person not obligated in the fast? Is it completely permitted for him? Did the Sages not only permit him to eat according to need, and if it suffices for him to drink then he may not eat, and if it suffices for him to eat once then he may not eat a second time?”; Maharil Diskin Kuntrus Achron 75

[5] See Michaber 554:6 and so is implied from Setimas Haposkim, and all Poskim who rule that one who is sick and ate cannot be called for an Aliyah. Vetzaruch Iyun!