Eating Shiurim on Tisha B’Av

Question: I take regular medication and have managed successfully to fast on Yom Kippur by eating a small piece of cake and a shot of juice with my pills. What do I do on Tisha B’Av?

Answer: A choleh she'ain bo sakana is defined as one who is confined to bed as a result of their illness (See Shulchan Aruch and Rema OC 328:17). The Shulchan Aruch (OC 618:7) and Mishna Berura (618:18) explain how one in this category should eat shiurim (less than a kezayis in a short amount of time) on Yom Kippur.

The Aruch Hashulchan (OC 554:7) writes that there is no concept of shiurim on Tisha B'Av. Likewise, the Mishna Berura (554:16) writes that Tisha B'Av is like any other Rabbinical fast whereby a choleh she'ain bo sakana should break their fast. However, in the Biur Halacha (554:6), he writes that if they can manage to eat in shiurim on Tisha B'Av they have not technically broken their fast.

R' Avraham Avraham (Nishmat Avraham OC 554:5:1) quotes R’ Shlomo Zalman Auerbach and R’ Shmuel Wosner who explain that only one who is eating to prevent becoming ill should utilise shiurim. However, one who is ill should eat normally. He quotes the Sdei Chemed (Bein Hametzarim 2:3) who writes that one must listen to medical advice rather than decide oneself.

In conclusion, one who is ill (choleh she'ain bo sakana) should not fast at all on Tisha B’Av. However, one may eat a little bit of food (shiurim) in order to prevent oneself from becoming ill, though one must consult with a Rabbi and doctor before doing so.