What is the reason for doctors to tell you to start fasting?

There are different reasons as to why, it depends what tests you’d be put through

Short fasts are common where anaesthetics would be required such as surgey but thats generally half a day or thereabouts.

Maybe is some sort of bowel test that requires them to be emptioer, never heard of a week before but I'm not a medical expert.

What were you at the doctor for? I'm guessing if they have asked you to go back it was more than just a general checkup.

It sounds like they want you to fast for a test. But that would only be 24 hours max

You should have asked them why they wanted you to fast for a week! It is not normal for anyone to fast for a week other than possibly spiritual reasons. If you really wish to know why, please give them a call and ask them the purpose for the fast. Even if you were overweight, that would be a stupid reason for a week fast.

Have a wonderful day

Ring the nurse and confirm exactly what is required.

Sometimes you need to do a fasting blood test a week later but you only need to fast for 12 hours before the test.