Fluke or Trend? Fasting Prior to Cholesterol Test
Alvin B. Lin, MD, FAAFP
Dr. Lin is an associate professor of family and community medicine at University of Nevada School of Medicine and an adjunct professor of family medicine and geriatrics at Touro University Nevada College of Medicine. He also serves as an advisory medical director for Infinity Hospice Care and as medical director of Lions HealthFirst Foundation. Dr. Lin maintains a small private practice in Las Vegas, NV. The posts represent the views of Dr. Lin, and in no way are to be construed as representative of the above listed organizations. Dr. Lin blogs about current medical literature and news at http://alvinblin.blogspot.com/.
When was the last time you checked your cholesterol? Sugar? Have you been putting it off due to the inconvenience of fasting overnight prior to the blood draw? When we check your "cholesterol", we're actually checking Total, HDL (good) & LDL (bad) Cholesterol, in addition to Triglycerides. It's the Triglycerides that go up immediately after a meal, which is why we want you to fast beforehand. HDL & LDL aren't affected in the short-term. Although we recommend exercise to hike your (healthy) HDL and better nutrition to lower your (lousy) LDL (get it?), it turns out that shrinking that belly (goal less than 40" in men & less than 35" in women) is the best way to decrease your Triglycerides.
But back to the original question. You've got to know where you are in order to figure out where you're headed. As luck would have it, a cross-sectional evaluation of a community dwelling cohort was published in Archives of Internal Medicine earlier this week in which the authors concluded that there's no reason to fast prior to checking cholesterol. Granted, they had a lot of data by studying the results of 209,180 men & women (avg 53yo) relative to their last meal versus their blood draw. As expected, LDL did not vary by more than 10% depending upon mealtime. Surprisingly (for me), Triglycerides only varied by no more than 20% depending upon mealtime.
Remember that when you calculate your risk for a heart attack over the next 10 years, regardless of whether you use the Framingham calculator or Reynolds Risk Score, we're focused on meeting an LDL goal first. HDL & Triglycerides are secondary goals. And truthfully, over the last year or so, numerous studies have shown that nothing we throw at them, whether niacin or fenofibrate, makes a difference to event rates, what really counts to you and me. So if that's the case, perhaps the accuracy of your Triglycerides doesn't really matter as much, seeing that we can't seem to do anything about it anyway. In which case, there's no reason to postpone & fast for your cholesterol blood test, right?
Except that checking your glucose (sugar) for diabetes is always a good idea and definitely requires you to be fasting . . .