Fasting before a cholesterol blood test

[Wonga]

Is it necessary to fast 12 hours before a cholesterol and triglycerides blood test, and drinking a pint of water 1/2 hour before the test, as my clinic, where they take the blood at 8am, requests?

How much of a difference to the figures can it make, and is it of physiological significance?

[lars999]

Hello Wonga,

It is widely stated that concentration of cholesterol, triglycerides, lipoprotiens in blood plasma varies widely during the day because of eating, digesting, etc. As far as I know, fasting for 12 hours before blood is drawn for these analysis has been SOP for past 50-100 years. Purpose, of course, is to give reproducable results.

The drinking of water before having blood drawn facilitates that process. Makes it far easier to draw blood because blood is more fluid from the additional water. Decades ago I was involved in medical situation where both fasting and no drinking of any fluids was required for 12 hours before drawing blood -- often problem with blood being too thick to get adequate sized sample -- so, we would have to drink a big glass of water, wait 15 minutes and nurse tried again, usually successful.

Lars

[Wonga]

If someone goes on a total food fast, his blood glucose will not change at all, even just before death, 3 weeks later.

My question is: what happens to blood cholesterol level during a toatl food fast: does it remain the same or drop 20%?

Or does cholesterol production from the liver actaully rise, as the body digests its own fat and protein?

[tuts1230]

Hi,I fasted the twelve hours before I had my sample taken and the last drink I had was a glass of apple juice and no water.My result came back ok except for my potassium level was raised by a lot and I was told to cut back drastically on any salt I had in food but this had not reared its head before so I put it down to the apple juice.I drink the apple juice to reduce my liver enzyme reading and it does this ok.I am not a big drinker but alcohol doesn,t like me but I am not prepared to abstain fully as I have given up a lot and a drink now and then makes my day.

[MichV]

Do results (any results) of a blood test matter if it's taken in the extreme a.m. (like 7-8am) compared to later (5-8pm)? I'm sure there are different processes that go on in the body depending on light levels, heart rate, oxygen, food, exercise, etc. Plus what if you went to bed hungry? Wouldn't that give a false low blood sugar reading?