If a person has type 2 diabetes and still would like to observe fast – like during the Muslim month of Ramadan, here is an excellent article on The Ismaili: Nutrition Centre with some guidelines and checklist to consider.

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A recently study concludes that most people with well-controlled type 2 diabetes can safely observe the fast. The study was published in the July 2008 issue of Clinical and Experimental Hypertension.
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# Do not stop taking your medication, however the dosing and timing of your medication may need to change – this should be discussed with your diabetes healthcare team prior to fasting.
# If you experience symptoms of low blood sugar levels such as sweating, anxiety, shaking, weakness or confusion then you should break your fast with a sugary drink followed by foods rich in carbohydrates.
# Avoid eating lots of unhealthy foods as a reward! Instead, try and maintain a healthy eating pattern after you break the fast.
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More at source: Fasting and Diabetes