Practical list of Shiurim for food and drink for a sick or pregnant woman who cannot fast:

• Food:[1] A sick person, or person with a medical condition, who has been instructed to eat less than the Shiur, is to eat less than the size of a Kusebes, which is less than 30 cc and 30 grams, within the amount of time it takes to eat a Peras of bread, which is nine minutes: The food is measured based on volume and[2][3] Hence, the Shiur is [less than[4]] the amount of food to fill 30 cc in a measuring cup [or typical match box], and this amount itself is not to weigh more than 30 grams.[5] One is not to eat more than this amount of food within nine minutes.
• Drink: A sick person, or person with a medical condition, who has been instructed to drink less than the Shiur, is to drink within nine minutes less than the amount of water that can fill one cheek. Hence, before Yom Kippur, he is to fill a cheek with water, pour it into a cup, and mark the water level on the cup. When there is Halachic need to drink based on the Shiurim, one is to drink less than this marked amount of liquid within every 9 minutes. One is not to drink the exact amount marked, as this is the Shiur Kareis for liquid.
• Eating and drinking within the nine minutes: All foods join each other to make up the minimum measurement of 30cc, and all liquids join each other to make up the minimum measurement of Malei Lugmav for Kareis liability. Nevertheless, foods and liquids do not join each other. [See above Halacha 4D] Accordingly, a person may both eat and drink less than the Shiur of eating and drinking within the 9 minutes as they do not join each other, and there is no need to take turns between eating and drinking every 9 minutes.

The amount of time to eat the Shiurim:

All the food and liquid that one consumes within nine minutes is counted as part of the Shiur. Meaning, that one should make sure not to eat the more than the Shiur of liquid or food within nine minutes, and hence the shiur restarts every nine minutes after completing eating or drinking less than the Shiur.^[6] If nine minutes is too long of an interval, one may go down to 8, 7.5, 6, 5, 4.5,4 minutes, as is medically necessary.[7]

Preparing the Shiurim before Yom Kippur:[8]

An ill person is to prepare the Shiurim before Yom Kippur. He is to fill one cheek with water and place it into a cup and then mark the water level. Alternatively, he is to fill both cheeks with water and measure half of that amount.[9]

How to measure the food:

One is to crumble the food and enter it into an area which holds 30cc, which is the common size of a match box.

If one is medically required to drink, must he nevertheless abstain from eating foods?

One is only allowed to eat and drink in accordance to his medical need, to prevent danger of life. 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.

List of conditions that typically require drinking and/or eating, upon directive of a doctor:

• Cancer:[10] In general, medical practitioners advise cancer patients that while it may be safe for them to fast from foods, they need to have constant consumption of liquid throughout the day. Practically, every cancer patient is to advise with his medical practitioner as to what he is to do.
• Anorexia and bulimia eating disorders:[11] For most cases, medical practitioners including dietitians and psychologists, prohibit fasting for a patient with an eating disorder who is going through treatment, and require them to eat normal meals. Eating disorders is the world’s most fatal mental and psychological illness, with a 20 to 30% death rate of those who are not treated, and a 5% death rate for those who are treated. Fasting, which ironically is something that those with eating disorders have pleasure in doing daily, can cause those who are in treatment to have setbacks and relapses to their illness, and hence limiting or regulating their eating on Yom Kippur can be defined as Pikuach Nefesh. Practically, one with an eating disorder of the above nature may not fast without first discussing the matter with their medical practitioners and Rav.
• Renal disease-Kidney stones: One who suffers from kidney stones will typically be directed by a doctor that he is obligated to drink plenty of liquids even on Yom Kippur. Lack of fluids can lead to complications which can lead to surgery and a state of Pikuach Nefesh. Each individual is to speak to his doctor for a directive for his condition.
• Diabetes:[12] One who suffers from diabetes, especially Diabetes mellitus Type I, must confer with their doctor regarding options of fasting.
• Cellulitis: While Cellulitis is certainly a lethal infection it is bacterial and therefore fasting could even be proved to be beneficial in healing it.[13] Practically, one is to advise with his doctor, although typically it is not dangerous for him to fast with Cellulitis.
• High and low blood pressure: https://health.clevelandclinic.org/fasting-how-does-it-affect-your-heart-and-blood-pressure/#:~:text=Research%20shows%20that%20fasting%20can,a%20secondary%20impact%2C%E2%80%9D%20Dr.

[1] Piskeiy Teshuvos 618; Shiurei Torah 3:10

[2] So is implied from Shiureiy Torah ibid towards end that by a food which weighs more than water it is to be less than 30 grams and less than 30 cc.

[3] Shiurei Torah 3:10, unlike Kaf Hachaim [and so rules Yalkut Yosef] which measures all based on weight.

[4] As 2:3 of an egg, which is the Shiur of the Kuseves [618:13] is 30 cc. [Shiureiy Torah ibid] Vetzaruch Iyun as Admur there writes 2:3 of an egg or a little more is the Shiur of a Kuseves, hence there is no exact Shiur. In any event seemingly to be on the safe side one is to eat less than that amount, and so is implied in Shiureiy Torah ibid. However, from Piskeiy Teshuvos 618:8 it is implied that one may eat that amount Vetzaruch Iyun.

[5] So is implied from Shiureiy Torah ibid towards end that by a food which weighs more than water it is to be less than 30 grams and less than 30 cc.

^[6] Chasam Sofer 6:16; M”B 618:21; Shiurei Torah 3:15 [p. 203]; Aruch Hashulchan 202:8; Kaf Hachaim 210:5; Piskeiy Teshuvos 210:1; Sefer Haminhagim ibid and footnotes 342-344;

Opinion of 6-7 minutes: The Tzemach Tzedek [Shaar Hamiluim 1:8-10] records 6-7 minutes regarding the Shiur of Achilas Peras. [Ketzos Hashulchan 36 footnote 5; 59 footnote 4; Shiureiy Torah ibid footnote 35; Sefer Haminhaghim [English] p. 93 regarding Tisha B’av]

[7] Shiureiy Torah ibid

[8] M”B 618:21; Rav Cohen

[9] Shiureiy Torah 3:17 footnote 32; Nitei Gavriel 41:5

[10] See here: https://1drv.ms/w/s!As_LDRax2-j3guJCxsyrgZTq-882wA?e=Wd4qGP   

[11] See Admur 618:2 that even if death will not occur right away, but will cause a deterioration of the life-threatening illness, that it is viewed as Pikuach Nefesh; Chashukei Chemed Yuma 83a; Koveitz Asya 99 p. 97-100; See here: https://1drv.ms/w/s!As_LDRax2-j3hbRILSibLWTwamAt9g?e=pt78hu

[12] See Techumin 29:362 and here: https://1drv.ms/w/s!As_LDRax2-j3guJHpOdVu7X1hVxUCA?e=Nq2PMJ

[13] https://www.youtube.com/watch?v=hYxDuTfrP2Q