Not taking thyroid meds before blood test.

[Gerbils3433]

I see on this site that you should not take your thyroid medication for at least 24 hrs before a blood test. My GP has never mentioned it to me and infact when I mentioned it to her she just looked at me as though I was mad. I must remember in most cases when dealing with the medical professionals, that I should be my own advocate and seek knowledge elsewhere!

[Jaydee1507 Administrator]

This is a patient to patient tip and most medics will have no idea about it. Doctors don't know how to make us well which is why this group is so busy.

Keep learning and reading here and you will go far.

[SeasideSusie Remembering]

I see on this site that you should not take your thyroid medication for at least 24 hrs before a blood test.

Slight inaccuracy there which I'm pointing out so that other members wont make a mistake in timing.

The advice we give regarding timing of thyroid meds is as folllows:

* Last dose of Levo 24 hours before the test

* Last dose of T3 or NDT 8-12 hours before the test with dose being split the day before the test into 2 or 3 doses

This avoids any false high hormone levels by taking them too close to blood draw or any false lows by leaving too long a gap.

[shaws Administrator]

Yes, we are going along the right path when we ignore the majority of GPs advice.

Many members have more knowledge than GPs or whomsoever is dealing with patients who have a dysfunctional thyroid gland.

One of my GPs phoned to tell me that my blood test was fine and I had no problems. I cried because I felt so unwell.

He did not understand that a TSH of 100 would diagnose the patient had hypOthyroidism.

We're better off using this Forum as we can rely upon the information given to us.

if you click on my name you can read my background when I was finally diagnosed.

[waveylines]

It does say it in the instruction leaflet for Levothyroxine. Maybe the GP should try reading it! 🤣😅🙄

[nara8 in reply to waveylines]

Which brand of levo do you take? I take Euthyrox. The leaflet doesnt have any information about blood test timing.

[waveylines in reply to nara8]

Ahhh.... How strange. Well it used to when I took levothyroxine. I'm on NDT. I shall have a nosey and see whst that says....

[waveylines in reply to nara8]

Hi Narag. I've had a look and you are correct..... Now there is no advice about not taking levothyroxine for 24hrs before testing. Infact it says it make no difference to the TSH. However there's no mention of the effect on the Ft4.....!!! l can't see a mention of not taking it anywhere in my Armour advice. Though online the recommendation is not to take it till after the test.

This was not the case when I started treatment over 20yrs ago. I think it's probably because they are relying on TSH only as a guide to treatment..... Despite the evidence that this approach leads to under treatment!

So my apologies.

[nara8 in reply to waveylines]

Wavylines, I didn't mean not taking thyroid medicine before the blood test was wrong. I just wanted to download the leaflet of the medicine you are taking. I have a really bad memory I can't remember the articles I've studied. But this is a file presented by a pathologist in a congress( sorry it wasn't a congress.I checked) but the reference of this part isn't mentioned.

Serum T4 & FT4 concentrations peak 2-4 hours after an oral dose of LT4. They remain above normal for approximately 6 hours in patients receiving daily replacement therapy. TSH and T3 levels are not affected by LT4. So, it is recommended that blood sampling for T4 & FT4 measurements be performed before taking any thyroid medication.

It’s important to be aware that T3 has a half-life of around 8 hours. FT3 levels increases after taking T3-containing medication and reach a peak after 3-4 hours. Straight after taking a T3 containing medication, the TSH level begins to fall and then stays suppressed for as long as 5 hours. So, it is recommended to hold off taking T3-containing medication until after the blood sampling

Suggestions:

_ At least 2-3 hours fasting before sampling

_ Monitoring of TSH level in each patient at the same time, and under the same circumstances.

_ For thyroid hormone measurements, blood sampling should be performed before taking thyroid medications

[waveylines in reply to nara8]

I didn't read it like you meant that Narag.... No worries. 😊😊

[helvella Administrator Thyroid UK in reply to nara8]

There are dozens of PILs for Euthyrox as they are tailored to each of the many countries to which it is supplied - and in many languages.

A current English-language version from Merck's own website in Germany does not seem to mention a gap - as far as I can see.

euthyrox-instructions.com/c...

I don't remember it being an issue mentioned in any PIL or equivalent. Though in my view, it most definitely should be.

[waveylines in reply to helvella]

It certainly used to be mentioned Helvella..... But then so much of importance has been chucked out.... Sigh...

[helvella Administrator Thyroid UK in reply to waveylines]

Just checked a 2015 Eltroxin PIL and this is the only reference to blood tests:

Screenshot of 2015 Eltroxin PIL snippet

[waveylines in reply to helvella]

When I was on levo it was way before that Helvella..... Think around turn of the millennium.... unless I dreamed it up. 😁

[DawnD]

When I raised this issue with the British Thyroid Foundation, they told me that there was no problem with taking thyroxine before a test, and to continue to take it as normal, as it was a slow release medication. I didn't get a chance to think about it this year as I took my normal thyroxine on Friday morning, phoned up later to book my annual health check, and was told I could take an 11 o'clock cancellation for my blood test! Will find out on Tuesday what the results are!

[helvella Administrator Thyroid UK in reply to DawnD]

FT4 peaks around 2 or so hours after ingestion.

It is NOT a slow release medication.

It is a standard (or fast) release medication.

Could read that as someone misunderstanding "release" and assuming "effect on TSH"!

[tattybogle]

2 research papers recommending early a.m. blood testing before taking that days dose,

see 3rd reply to this post : healthunlocked.com/thyroidu....