Blood test

[Baileyleigh123]

I am going for my blood test this morning for my thyroid and vitamins and iron levels checking I was advised on here not to take my thyroxine before I go is this correct and if so what is the reason for this thankyou

[pennyannie]

Hello Baileyleigh :

In a word or two : because you will be measuring what you have just ingested and it will give you a " false high " reading of T4 :

The blood tests should reflect what your body is " holding onto " and not the dose you have just taken:

T4 - Levothyroxine is a storage hormone and we need to know what your store level is :

T4 is inert - it is not "active " you won't " miss it " - don't worry - take it after the blood draw :

[Baileyleigh123 in reply to pennyannie]

Oh thankyou for the reply makes more sense now to me x

[shaws Administrator in reply to Baileyleigh123]

The following link might be of interest:-

clinicaltrials.gov/ct2/show...

Below is an excerp from the above link:-

Background:

- Hypothyroidism is a condition caused by the loss of function of the thyroid gland. The thyroid gland produces two hormones, T4 and T3. These hormones control the metabolism and function of many organs. Lack of energy, depression, and constipation are common symptoms of hypothyroidism.

T4 is converted into T3, the active form of thyroid hormone, by two enzymes called deiodinases. People with hypothyroidism are treated with a synthetic T4 hormone, which the enzymes convert to T3. This treatment is usually effective, but some people continue to have symptoms even after treatment. Some researchers think that this may be caused by a problem with the enzymes that convert T4 into T3. They want to look at how the enzymes regulate the levels of T4 and T3 in the blood. They will do so by using a drug that blocks the action of one of the two enzyme

clinicaltrials.gov/ct2/show...

[SlowDragon Administrator]

Always test thyroid levels as early as possible in morning before eating or drinking anything other than water and last dose levothyroxine 24 hours before test

You want to measure the lowest levels of Ft4….not the highest

Ft4 peaks rapidly after taking levothyroxine

[Baileyleigh123]

Thankyou x

[shaws Administrator]

It should also be a 'fasting' blood test.

[Baileyleigh123 in reply to shaws]

What do you mean please x

[shaws Administrator in reply to Baileyleigh123]

You should not eat before your blood test i.e. that's why the advice is for the earliest blood draw and fasting (you can drink water, but don't eat until after the blood is drawn.)

🙂

[Baileyleigh123 in reply to shaws]

Thankyou x

[Marz]

Do you have the results for the vitamin and iron testing mentioned in your opening post ?