Do I fast for blood test

[Pittsburgh]

Do I need to fast before blood test

[Rmichelle]

Hello there for any thyroid bloods to be taken it is recommeded that you try and get a early morning appointment and dont eat anything until after the test and dont take your thyroid meds until the test is done, so if you take your meds say at 8am in morning dont take it until test over with, if you take your meds in the evening say bedtime then dont take on that evening before appointment.

Doctors dont tell you that you have to fast but everyone here will say you need to as it does effect the readings. Hopefuly someone else will be along sbortly and will explain better than me.☺

[SeasideSusie Remembering]

Pittsburgh Rmichelle is correct. We always advise

1) Book the earliest appointment of the morning

2) Fast overnight - water allowed, breakfast after the test

3) Leave off Levo for 24 hours - take after blood draw

This gives the highest possible TSH which is needed when looking for an increase in dose of thyroid meds or to avoid a reduction.

TSH is highest early morning and lowers during the day, it also lowest after eating.

Most doctors don't know or deny this.

[Pittsburgh in reply to SeasideSusie]

thank you both so much. I didn't get this in time so i am going to cancel todays ampt and go Monday. You are correct , my Dr never said any of this

Learning so much here

[Pittsburgh in reply to SeasideSusie]

what do you me missed after eating?

[SeasideSusie Remembering in reply to Pittsburgh]

Stupid autocorrect! Should have been lowest after eating. Corrected now

[Pittsburgh in reply to SeasideSusie]

I have never taken the blood tests correctly on 10 years. No one ever told me this. Wonder how diff this one will be?

[Phoenix605 in reply to Pittsburgh]

The main key is consistency. Always taking meds with food or coffee or later tests is not best practice but as long as you always do the same you will get comparable results. The risk is it might alter the numbers just enough that you dont get that one last 25mcg that makes all the difference to feeling well.

[Pittsburgh in reply to Phoenix605]

I have always taken my rx w breakfast. I figure the dose at this point has been adjusted based on that. But I will now fast to test. I have never fasted fir testing either. My Dr has not problem incr. rx based on how I feel rather then any number So I'm thinking I've been ok. Would u agree ?

[Phoenix605 in reply to Pittsburgh]

If your doc is adjusting based on symptoms then no real need to change anything but worth considering if doc changes in the future. Yes your dose will have been adjusted based on the way you take it, suddenly changing to not taking with food could upset the apple cart. Most docs are TSH fixated so more relevant to us poor mortals with less enlightened ones 😁

[Phoenix605]

Yes you do, eating will affect your TSH by lowering it. TSH also follows a circadian rhythm, it peaks in the early hours so the earlier you can test the better and it is recommended by 9 am at the latest. If you take any supplements that contain biotin stop them for a few days, a week if poss before the test. Some thyroid tests use a biotin assay so taking it can skew the results. Taking thyroid meds before test will just measure the T4 you have just taken, if you take it at night miss that dose until after the test. T4 is a storage hormone so you will not notice the lateness of one dose.

Early fasting verses late having eaten can mean the difference between getting a dose raise or cut so worth the effort, GPs have no idea and most will say it makes no difference, I prefer to err on side of caution and the papers Ive read!