<s>[INST] Hi,My right kidney is scarred and is atrophic. according to doctor it is working less than 5%. i am a muslim , will be it be alright for me to fast for 30 days - i cant take water or anything else at all. i will be keeping fast 4 in the morning and breaking it at 8.30 pm in the evening. Can you please help. The left kidney is working fine and is of normal size but right kidney is less than 50mmThanks in advance [/INST] Hi, As you have solitary functioning Lt kinda, which is normal as you mention. However, you not mention the GFR and the cause of damage in the rt kidney, which sometime effect the opposite kidney also. The fasting will unlikely to affect your kidney keeping that you should avoid exertion or any activity with lead to deny Chat Doctor.  So a person with normal solitary functioning kidney are just like normal person with two kidneys except they have less renal reserve. Hope, I gave your answer </s>