How should I prepare for a TSH, T3 & T4 blood t... - Thyroid UK

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How should I prepare for a TSH, T3 & T4 blood test?

timmysmom profile image
8 Replies

I asked my gp if I could try increasing my levothyroxin from 50mcg (after being on it for 7 years with no improvement) to see if it helps with fatigue and brain fog but she said 'no, not unless you're bloods indicate you need it increasing.' So I'm due to have another blood test (TSH, T3 and T4).

I seem to remember reading somewhere on here that you should not take your levothyroxin on the morning of the blood being taken and I think there was something else about not eating? Is that correct?

I've search through some posts but can't find it.

Thanks in advance.

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timmysmom
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Manfe85 profile image
Manfe85

I have 3 monthly checks on my thyroid and have never once been told to stop my meds before the blood tests or change food habits etc... If it was needed they would have told you before hand, if you stopped your thyroxine then the results wouldn't be accurate and your T3 and T4 would be low from lack of meds. If it's low WITH your meds then you need an increase, but it's dangerous to increase if not needed so please don't choose to up your dose yourself. The side affects can be bad. Hope it all goes well for you x

SeasideSusie profile image
SeasideSusieRemembering

timmysmom

Doctors tend to have very little training on the thyroid in med school (someone on here once said it's one afternoon) so they often have little understanding of it and how to treat it.

A couple of our members have had excellent endos who have given the same advise as we always give here which is:

When doing thyroid tests, we advise:

* Book the first appointment of the morning, or with private tests at home no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If we are looking for a diagnosis of hypothyroidism, or looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.

* Fast overnight - have your evening meal/supper as normal the night before but delay breakfast on the day of the test and drink water only until after the blood draw. Eating may lower TSH, caffeine containing drinks affect TSH.

* If taking thyroid hormone replacement, last dose of Levo should be 24 hours before blood draw, if taking NDT or T3 then last dose should be 8-12 hours before blood draw. Adjust timing the day before if necessary. This avoids measuring hormone levels at their peak after ingestion of hormone replacement. Take your thyroid meds after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.

* If you take Biotin or a B Complex containing Biotin (B7), leave this off for 7 days before any blood test. This is because if Biotin is used in the testing procedure it can give false results (most labs use biotin).

These are patient to patient tips which we don't discuss with doctors or phlebotomists.

A blood test is only a snapshot of what's in the blood at the exact second the blood is drawn and should not be taken on it's own to base dose on but unfortunately doctors seem to have lost the skill of taking a patient's clinical signs and symptoms into account too.

If your dose of medication is too much or too little then your symptoms are going to tell you that anyway and a doctor should take that into account as well as the numbers.

To have been on 50mcg for 7 years is ridiculous, that is a normal starter dose, most people end up with a dose somewhere between 100mcg and 200mcg.

We are all individual as to where we need our levels to be, but in general the aim of a treated hypo patient on Levo is for TSH to be 1 or below and FT4/FT3 in the upper part of their reference ranges if that is where you feel well.

Get into the habit of always asking the receptionist for a printed copy of your test results a few days after the test. Some surgeries have online access but not all, so if yours aren't online then always get a print out.

Come back with new results when you have them, and please include the reference ranges as these vary from lab to lab.

timmysmom profile image
timmysmom in reply to SeasideSusie

Thank you so much Seaside Susie for that very comprehensive and detailed reply. I will follow the advice leading up to having blood draw. And I will post my results on here when I have them.

Thanks again for taking the time to reply.

SlowDragon profile image
SlowDragonAdministrator

You also need vitamin D, folate, ferritin and B12 tested

Likely far too low when left on starter dose levothyroxine

timmysmom profile image
timmysmom in reply to SlowDragon

Thanks Slow Dragon, I've heard that B12 deficiency can be more common if you have Hasimotoes but did not know about the vit D, folate and ferritin.

I'll post results on here when I have them. Thanks again.

SlowDragon profile image
SlowDragonAdministrator in reply to timmysmom

Low vitamin levels and hashimoto’s

ncbi.nlm.nih.gov/pubmed/286...

Vitamin D deficiency is frequent in Hashimoto's thyroiditis and treatment of patients with this condition with Vitamin D may slow down the course of development of hypothyroidism and also decrease cardiovascular risks in these patients. Vitamin D measurement and replacement may be critical in these patients.

endocrine-abstracts.org/ea/...

Evidence of a link between increased level of antithyroid antibodies in hypothyroid patients with HT and 25OHD3 deficiency may suggest that this group is particularly prone to the vitamin D deficiency and can benefit from its alignment.

ncbi.nlm.nih.gov/pubmed/186...

There is a high (approx 40%) prevalence of B12 deficiency in hypothyroid patients. Traditional symptoms are not a good guide to determining presence of B12 deficiency. Screening for vitamin B12 levels should be undertaken in all hypothyroid patients, irrespective of their thyroid antibody status. Replacement of B12 leads to improvement in symptoms,

Folate supplements can help lower homocysteine

ncbi.nlm.nih.gov/pmc/articl...

Levothyroxine can decrease serum homocysteine level partly; still its combination with folic acid empowers the effect. Combination therapy declines serum homocysteine level more successfully.

Low ferritin frequent in hypothyroidism

endocrineweb.com/profession...

Non Coeliac Gluten sensitivity (NCGS) and autoimmune disease

ncbi.nlm.nih.gov/pubmed/296...

The predominance of Hashimoto thyroiditis represents an interesting finding, since it has been indirectly confirmed by an Italian study, showing that autoimmune thyroid disease is a risk factor for the evolution towards NCGS in a group of patients with minimal duodenal inflammation. On these bases, an autoimmune stigma in NCGS is strongly supported

ncbi.nlm.nih.gov/pubmed/300...

The obtained results suggest that the gluten-free diet may bring clinical benefits to women with autoimmune thyroid disease

nuclmed.gr/wp/wp-content/up...

In summary, whereas it is not yet clear whether a gluten free diet can prevent autoimmune diseases, it is worth mentioning that HT patients with or without CD benefit from a diet low in gluten as far as the progression and the potential disease complications are concerned

timmysmom profile image
timmysmom in reply to SlowDragon

Thanks Slow dragon, I've been self injecting hydroxocobalamin for 5 weeks now as my husband who has B12 deficiency does. We've both been using a vit D mouth spray from Holland and Barrett, is this a good way to take vit D?

Thanks.

SlowDragon profile image
SlowDragonAdministrator in reply to timmysmom

Vitamin D spray by Better You

What dose?

They now make one that contains vitamin K2 mk7

As you are taking B12 are you also taking vitamin B complex?

one with folate in not folic acid may be beneficial.

chriskresser.com/folate-vs-...

B vitamins best taken in the morning after breakfast

Igennus Super B complex are nice small tablets. Often only need one tablet per day, not two. Certainly only start with one tablet per day after breakfast. Retesting levels in 6-8 weeks

Or Thorne Basic B or jarrow B-right are other options that contain folate, but both are large capsules

If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 7 days before any blood tests, as biotin can falsely affect test results

endo.confex.com/endo/2016en...

endocrinenews.endocrine.org...

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