Question About Fasting For Labwork

[loess]

So I've never had bloodwork done but recently took advantage of a discount on DirectLabs' Comprehensive Wellness Profile (thanks to Dan!) and am also getting an Iron panel done. Fasting for 12 hours is required, which I don't mind doing, but I can pretty much guarantee that I will run out of glycogen during that time and blood sugar will drop, resulting in a stress response, elevated cortisol, adrenaline, moodiness etc. Would this not throw off some of the readings being tested? For those of you who are experienced with bloodwork do you just not fast even if it is called for, or...?

 

[haidut]

I noticed the same thing - fasting for that long will elevate a number of stress hormones, which in turn will affect some of the other hormones being measured. Fasting raises prolactin, growth hormone, cortisol, adrenalin and ACTH. That will raise estrogen, serotonin, free fatty-acids, triglycerides, and possibly even some of the blood parameters measured in tests like CBC. Unfortunately, most US doctors will refuse to do a non-fasted blood test for diagnostic purposes, so if you end up doing the tests please use your knowledge to interpret them accordingly.
Just my 2c.

 

[loess]

haidut, your cents make sense

So if it's mostly the hormonal aspects that could be altered due to fasting, that's fine. Mostly I am interested in calcium/phosphorus/vitamin D/iron (things I have been intentionally trying to either supplement or limit consumption of) as well as the thyroid panel that's included in that test. I have a recently arrived supply of Cynoplus/Cynomel that I'd like to carefully ease into a low dose of, but in addition to tracking temps and pulse, I'd like to see what numbers come up in the labwork before I start in.

 

[haidut]

haidut, your cents make sense

So if it's mostly the hormonal aspects that could be altered due to fasting, that's fine. Mostly I am interested in calcium/phosphorus/vitamin D/iron (things I have been intentionally trying to either supplement or limit consumption of) as well as the thyroid panel that's included in that test. I have a recently arrived supply of Cynoplus/Cynomel that I'd like to carefully ease into a low dose of, but in addition to tracking temps and pulse, I'd like to see what numbers come up in the labwork before I start in.

I think fasting will lower calcium and maybe increase parathyroid hormone since it responds to calcium drop within 2-3 hours. Increased PTH will in turn lower serum vitamin D3 and increased active vitamin D (calcitriol) but how fast that happens I am not sure about.
Also, Ray wrote that just 1 hours of running will virtually remove all T3 from the serum due to the elevation of cortisol and adrenalin. So, it is reasonable to expect the same to happen with extended fast and you will probably get unrealistically low T3 numbers after a long fast.

 

[loess]

One of my motivations for getting blood work is that I'd like to get a baseline objective measurement on my vitamin D and calcium levels (I also wanted to get PTH tested but opted not to fork over the extra $). Reason being is that for several months I have been supplementing some eggshell powder with the intention of correcting what I suspected to be a longstanding deficiency in calcium as well as regular balancing of higher phosphorus foods (farmers cheese, oysters, liver, meat). But lately I'm feeling a little more cautious about it and wondering if I'm overdoing it, especially since I do already drink a lot of milk. In any case it will be interesting to see what comes up in the results.

 

[Such_Saturation]

At the very least I usually drink a little juice before I go to bed and after I wake up. Also keep in mind when you donate blood they let you eat and still run tests. I even told them I had drunk full-fat milk one time and they were worried about fat levels but let me do it nonetheless.

 

[BingDing]

I got a lot of blood work done recently and didn't have to fast for any of it. Maybe the iron test requires it, or just one test. Maybe you can do that separately.

 

[aguilaroja]

Some of the quite valid questions raised are unlikely to be researched carefully. There is no profit in it. Individual daily rhythms vary depending on person and circumstance. It is easier for practitioner to inconvenience patients than for research to get fuller answers and then educate.

AFAIK the reasoning for suggesting "iron studies" be done fasting is that a recent meal with high iron content can theoretically skew some of the results:

http://www.healthcommunities.com/blood- ... ests.shtml

"Blood samples should be taken early in the morning for the iron level test, since iron levels vary throughout the day.
While no fasting is required before a ferritin test, recent ingestion of a meal containing a high iron content (from red meat, for example) can cause elevated levels."

Glucose/insulin testing and lipid testing are other common ones for which fasting is usually requested. There are certainly questions about the importance of fasting for lipid blood tests. And forum readers are familiar with nonsense about orthodox cholesterol thinking.

http://www.apath.co.nz/why-do-i-need-fa ... lood-tests

http://www.webmd.com/cholesterol-manage ... terol-test

Some of the quite valid questions raised are unlikely to be researched carefully. There is no profit in it. Individual daily rhythms vary depending on person and circumstance. It is easier for practitioner to inconvenience patients than for research to get fuller answers and then educate systemically.

For most of the lab tests, fasting-or-not may be of small significance. What you are already doing is more important: understanding your own circumstances when the test is done, correlating the testing with your signs and symptoms, and understanding the aim and background of the tests.
AFAIK & IMNHE serum vitamin D level "snapshots" are fairly useful no matter what time of day, as long as the recent intake has been fairly consistent (no recent drastic change in oral dose). For mineral tests like serum calcium, it does not necessarily fully reflect what is in the cells, no matter the time of testing. There are various intracellular mineral tests (epithelium, whole red blood cell). But those are usually added out of pocket expenses and are only guideposts as well.

 

[loess]

This is all terrific info, thanks very much. I typically wake up depleted of glycogen and with symptoms that indicate very clearly that cortisol levels are sky high. I really can't function until I at least get some juice in me, so it's good to know that some OJ at the very least that day wouldn't be a dealbreaker here, and I can also plan to avoid any iron-rich foods in the 48 hours or so preceding the labwork.

 

[Such_Saturation]

Often albumin would go over range when I didn't eat or drink.

 

[RisingSun]

So I've never had bloodwork done but recently took advantage of a discount on DirectLabs' Comprehensive Wellness Profile (thanks to Dan!) and am also getting an Iron panel done. Fasting for 12 hours is required, which I don't mind doing, but I can pretty much guarantee that I will run out of glycogen during that time and blood sugar will drop, resulting in a stress response, elevated cortisol, adrenaline, moodiness etc. Would this not throw off some of the readings being tested? For those of you who are experienced with bloodwork do you just not fast even if it is called for, or...?

Fasting is extremely benefitial to health.

I noticed a ton of energy after 4 days of dry fasting (no food & no water)

How do you get scared about half a day without eating?