I have never heard of fasting for 20 hours as being normal. I work in pathology and the fasting period is between 10 to 12 hours with a maximum of 14 hours. If you fast over 14 hours the lab has to be informed as the test could indicate falsely that you have a medical condition that would not be there if you fasted with in the normal limits. Some collection centres will turn you away if you have fasted longer than 14hours.
I had my cholesterol checked 30 days apart, three times.
151, then 224, then 237.
I did not significantly change my diet or exercise. I fasted about 16 hours before each test.
The only thing they could think of was that I had eaten at a big, Indian day the day before, and they suggested I eat "normally" for 2-3 days, then come back (which I will do). However, I have heard that you don't need to fast more than 12 hours, and that if you eat high-fat foods the night before, it will skew your results.
I have been eating extremely healthy and working out like crazy, and there is no way my cholesterol should have shot up. The nurse practictioner was so shocked, she re-tested me for free.
Cholesterol is a waxy material that is produced by the liver is needed for generating vitamin D, some hormones, build cell walls and create bile salts which assist in digesting fat. Cholesterol is found in many food stuffs. Too much cholesterol creates heart problems and may cause serious health hazards.
Cholesterol screening is done to determine the cholesterol level in people's body. It is necessary to control the cholesterol level to a normal rate for health and fitness. High cholesterol causes an increased risk of coronary heart disease (CHD) and a thickening or hardening of the arteries that supplies blood to the heart muscle. It isn't necessary to fast before cholesterol screening but remember that the person undergoing the test or screening should not eat anything for 12 hours before the test. It is okay if the person consumes tea, coffee, milk or water.
The normal range for fasting varies from 12 to 20 hours and I don't think it will make any difference if you fast more than 14 but less than 20 hours.