Rueben Ramirez

burner of poptarts; breaker of things

Don't Fast (too long) Before Blood Work

Published December 11, 2023

Most doctors will advise 12 hours of fasting prior to getting blood drawn for lab work. This helps the labwork to tell the most accurate story of what’s going on with your body (without the noise of your body’s processing of a meal).

I didn’t know extended fasting prior to blood draw would be problematic. TIL the 62 hours that I had fasted prior to the blood draw causes the body to spike both bilirubin and cholesterol levels. This is an indication of active ketosis and autophagy. So all’s not lost. I learned that my body does what it’s supposed to do when I fast!

I’ll have to go back for more blood work to get accurate results. No extended fasting before blood labs no!

What is Ketosis?

Most people eat plenty of carbs and sugar and their bodies will use the resulting glucose as their primary fuel source. If you limit or cut out all sugar and carbohydrates from your diet, your body will use up the glucose reserves stored as glycogen in your muscle and liver tissue. Once all the glucose reserves are depleted, the body switches over to another fuel source: fat. The body converts fat to an ketones, and this is what your body will run on if glucose is not available.

Glucose is the body’s preferred energy source (it’s the easiest energy source to use), so once it’s available again (once you eat a bunch of carbs or something sugary) the body switches back to glucose. I switch my diet up periodically to cycle into and out of ketosis.

Why go through the trouble of limiting carbs and sugar? There are two big benefits I care the most about. Significant weight loss has been much easier for me to achieve while in ketosis. (if the body is burning fat for energy, it’s easy to drop the pounds). The other incredible benefit I’ve learned about more recently are the effects around reduced inflammation. Inflammation going down translates to fewer aches and pains, and promoting tissue recovery. (e.g. faster recovery from more intense workouts)

What is Autophagy?

Autophagy is a concept I’m still trying to wrap my head around. My current, admittedly light, understanding of autophagy is as a mechanism the body uses to heal itself. Once in an extended fasting state, the general idea is that the body starts rummaging around and gathering up older cells that no longer work as effectively as they once did. These older cells are then broken down and the various cellular components are then recycled for the purpose of new cell creation. So it’s something of a recycling system at the cellular level.

Autophagy starts when the body remains in a fasted state for 12-16 hours. Doctor’s don’t seem to agree on the timeline specifics here. I aim at intermittent fasting on a regular basis throughout the week. Once a month I’ll commit to a 2-3 day water only fast.

Why fast to induce autophagy? For me the benefits are around energy levels, inflammation reduction, and promoting the recovery of unhealthy organs. I fast primarily to stay on top of caloric restriction limits, but if there are additional benefits from fasting for a little longer, I’m happy to give it a shot…and so far I’m very happy with my recovery results.