It appears you have not yet Signed Up with our community. To Sign Up for free, please click here....



Thyroid Disorders Message Board
Post New Thread   Closed Thread
LinkBack Thread Tools
Old 01-17-2004, 11:55 AM   #1
Junior Member
 
Join Date: Jan 2004
Posts: 31
huh? HB User
Do you fast before labwork?

My first tests (T3, T4 and TSH) I fasted. My second set (FREE T3, FREE T4 and Antibodies) I did not. Does fasting make a difference?

Thank you!

 
Old 01-17-2004, 01:13 PM   #2
Senior Veteran
(female)
 
Join Date: Jan 2003
Location: Missouri, USA
Posts: 12,278
midwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB Usermidwest1 HB User
Re: Do you fast before labwork?

Everything I've read says that fasting from food is unnecessary for thyroid testing. But I skip my thyroid med on the morning of the day I'm tested. It can skew the results.

 
Sponsors Lightbulb
   
Old 01-17-2004, 06:22 PM   #3
Member
 
Join Date: Apr 2003
Location: applegate
Posts: 60
sissy1 HB User
Re: Do you fast before labwork?

Quote:
Originally Posted by midwest1
Everything I've read says that fasting from food is unnecessary for thyroid testing. But I skip my thyroid med on the morning of the day I'm tested. It can skew the results.
Just curious if your Doctor told you to skip your thyroid meds before lab work? It seems that not taking them would give a incorrect reading and would not show your levels as they would be on the meds. As far as not eating before thyroid test, fasting isn't necessary unless you do a cholestrerol test with it as I often do.

 
Old 01-17-2004, 07:46 PM   #4
Senior Veteran
(male)
 
Join Date: Aug 2001
Location: Euless, TX
Posts: 1,639
Meep HB UserMeep HB UserMeep HB User
Re: Do you fast before labwork?

Quote:
Originally Posted by sissy1
Just curious if your Doctor told you to skip your thyroid meds before lab work? It seems that not taking them would give a incorrect reading and would not show your levels as they would be on the meds. As far as not eating before thyroid test, fasting isn't necessary unless you do a cholestrerol test with it as I often do.
The online thyroid textbook at [url]www.thyroidmanager.org[/url] provides this information in regards to the timing of blood tests in relation to taking meds:

Quote:
Serum T4 concentrations peak 2 to 4 hours after an oral dose and remain above normal for approximately 6 hours in patients receiving daily replacement therapy. The long half-life of thyroxine of about 7 days allows treatment with a singly daily tablet...
...
Liothyronine. After oral administration of L-triiodothyronine sodium (which is more readily absorbed than T4) peak levels of serum T3 are observed within 2 to 4 hours...The half-life of T3 is approximately one day.
...
Dessicated thyroid (Armour--Because of the relatively high ratio of T3 to T4 in desiccated thyroid, patients receiving an amount of this medication adequate to normalize serum TSH generally have serum T4 concentrations in the lower half of the normal range. Serum T3 concentrations will vary in such patients, depending on the interval between ingestion of the medication and the time of blood sampling.
...
The time course of the absorption of T3 is similar whether it is contained in thyroglobulin or free in the tablet, with peak levels approximately 2 to 4 hours after oral administration
What this all means in normal language is that a within a few hours after taking your thyroid meds--regardless of what you take--your T3 and/or T4 will be abnormally high for up to 6 hours. Some doctors know to compensate for this when they look at the labs but most do not. How many times has your doctor asked you what time you took your meds on the day of your labwork? Never? I thought so.

Keep in mind any time you do a lipid profile (cholesterol/triglycerides) or CMP or any type of glucose testing you SHOULD fast.
__________________
Danny

I am not a doctor, nor have I ever played one on TV...

Last edited by Meep; 01-17-2004 at 07:50 PM.

 
Old 01-18-2004, 05:07 PM   #5
Senior Veteran
 
Join Date: Jun 2003
Posts: 738
AngelaA HB User
Re: Do you fast before labwork?

If you take meds in the morning and then head down to the lab your FT4 & FT3 will be artificially high. I was never told this by my dr. I first heard about it online, then a co-worker told me her dr had reminded her not to take the med for the test. I either don't take Naturethroid before my test or wait till after work to go to lab. I know it makes a big difference as before the way I felt didn't match what my test results said, but now my tests "look" like I feel and was able to finally get my dosage increased after complaining for months that I was still hypo.

 
Old 01-19-2004, 08:17 AM   #6
Member
 
Join Date: Apr 2003
Location: applegate
Posts: 60
sissy1 HB User
Re: Do you fast before labwork?

Quote:
Originally Posted by AngelaA
If you take meds in the morning and then head down to the lab your FT4 & FT3 will be artificially high. I was never told this by my dr. I first heard about it online, then a co-worker told me her dr had reminded her not to take the med for the test. I either don't take Naturethroid before my test or wait till after work to go to lab. I know it makes a big difference as before the way I felt didn't match what my test results said, but now my tests "look" like I feel and was able to finally get my dosage increased after complaining for months that I was still hypo.
I can't believe in10 years since I was diagnosed with Graves Disease and subsequently lost my thyroid via radiation, that I was never told that it made a difference when you got your lab work done. I always thought you should have your meds in you before your lab work, which many times I've had my lab work done in the morning. I recently changed doctors and he ordered new labs and I took my meds in the morning and tested in the afternoon and he came to the conclusion my synthroid was too low. He raised it and my metabolism is noticebly higher. Thanks for sharing this.

 
Old 01-19-2004, 08:22 AM   #7
Member
 
Join Date: Apr 2003
Location: applegate
Posts: 60
sissy1 HB User
Re: Do you fast before labwork?

Quote:
Originally Posted by Meep
The online thyroid textbook at [url]www.thyroidmanager.org[/url] provides this information in regards to the timing of blood tests in relation to taking meds:



What this all means in normal language is that a within a few hours after taking your thyroid meds--regardless of what you take--your T3 and/or T4 will be abnormally high for up to 6 hours. Some doctors know to compensate for this when they look at the labs but most do not. How many times has your doctor asked you what time you took your meds on the day of your labwork? Never? I thought so.

Keep in mind any time you do a lipid profile (cholesterol/triglycerides) or CMP or any type of glucose testing you SHOULD fast.
Thank you for this information, you're right no Doctor has ever ask me when I took my meds in relation to the test. It seems they aren't concerned with how accurate they need to be with this medication to make us function right.

 
Old 01-19-2004, 07:07 PM   #8
Senior Veteran
 
Join Date: Jun 2003
Posts: 738
AngelaA HB User
Re: Do you fast before labwork?

Has any dr ever told you not to take iron containing vitamins or eat foods with calcium within 4 hrs of taking your thyroid med? None of my drs bothered mentioning it nor any of the pharmacists. The info was on the sheets that come from pharmacy stapled to the bag. But again its the patient who has to educate themselves as the medical "professionals" most likely won't.

Just an FYI I think decogestants and any steriodal type meds such as Cortef, prednisone or asthma inhalors would also affect thyroid test results. And thyroid meds would affect adrenal-cortex function tests.

Last edited by AngelaA; 01-19-2004 at 07:47 PM.

 
Closed Thread

Similar Threads
Thread Thread Starter Board Replies Last Post
Labwork Postie Lupus 1 05-04-2009 06:56 PM
how fast can your levels drop? GreenGal77 Anemia 6 02-16-2009 05:48 PM
Finally , labwork results..normal thyroid function? -was vit d deficient,hi ionizedCA kkl Thyroid Disorders 4 10-16-2007 07:23 AM
Slim Fast Success Stories? lam41565 Weight Loss 7 04-25-2007 12:36 PM
help with labwork AmyTx Lupus 1 03-31-2006 01:24 PM




Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Join Our Newsletter

Stay healthy through tips curated by our health experts.

Whoops,

There was a problem adding your email Try again

Thank You

Your email has been added




Top 10 Drugs Discussed on this Board.
(Go to DrugTalk.com for complete list)
Armour
Cytomel
Levothroid
Levoxyl
Potassium
  Synthroid
Tapazole
Unithroid
Xanax
Zoloft




TOP THANKED CONTRIBUTORS



sammy64 (668), midwest1 (627), FinnMaid (308), Reece (224), lisa789 (196), Tree Frog (80), mkgbrook (72), cd37 (56), ladybud (45), Bran'sNana (44)

Site Wide Totals

teteri66 (1165), MSJayhawk (1000), Apollo123 (898), Titchou (833), janewhite1 (823), Gabriel (758), ladybud (747), sammy64 (668), midwest1 (665), BlueSkies14 (610)



All times are GMT -7. The time now is 08:47 AM.



Site owned and operated by HealthBoards.comô
Terms of Use © 1998-2014 HealthBoards.comô All rights reserved.
Do not copy or redistribute in any form!