Skewing Blood Test Results FT3 and TSH. - Thyroid UK

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Skewing Blood Test Results FT3 and TSH.

AndiRiley profile image

I'm on prescribed 100mcg T4 and 20mcg T3. My endo is "concerned" about my suppressed TSH, but is continuing to prescribe at the current dose because I am clearly extremely well. How long this will continue I don't know, because the chief endo is on record as saying that he will not tolerate suppressed TSH. Sooooo, does anyone know how long I would have to be off T3 to get a TSH that is "in range"? How quickly does TSH respond? I know at least one patient stays off T3 for two weeks - is this necessary?

Latest test results: TSH under 0.03 (0.35 - 5.5) FT4 14 ( 10 - 19.8) FT3 4.4 ( 3.5 - 6.5) BTW, I have perfect housekeeping in terms of gluten free, vitamin levels etc.

I already avoid taking T3 for 15 hours prior to testing to avoid "scaring" my endo and GP with the spike after dosing. I have told my endo this and although surprised, he thinks it is actually an idea that is worth continuing with.

Interested in any info at all. Thank you.

7 Replies
shaws profile image

I am on T3 only. I just miss my once daily a.m. dose and have test and take it afterwards. My blood test results are fine.

I believe they are wrong by only taking account of the whereabouts of the blood test results and not relief of patients symptoms being a priority.

I think they don't know - or aren't aware - that if the patient takes other than levo, i.e. T3 (or T3 added to T4 ( or NDT) blood results cannot possibly 'fit' into the ranges which are for levo only.

Therefore if someone takes NDT or adds T3 or takes T3 only they cannot compare i.e. if on T3 only T4 will be low or very low and T3 high.

They should follow this regime and concentrate more on relief of patients' symptoms and use TSH for diagnosing. In the following link this doctor would never prescribe levo but only NDT or T3 only. Also before the 60's doctors only diagnosed us upon our clinical symptoms and prescribed NDT.

AndiRiley profile image
AndiRiley in reply to shaws

Thank you. My concern is how to try to get a TSH high enough to be "in range" to pacify an endo who is unable to accept all of this stuff that we know as educated patients with experience of self dosing according to how we feel.

If I can produce enough TSH for them on the day of the test, they will happily think they are doing a great job and continue giving me the medication I need :-)

I already fast, go as early as I can for blood tests and delay my once daily T3 - all of which lead to a raised TSH, but it's not enough in my case to get an in-range TSH. I am quite clear that my Hypothalamus/pituitary system has the wrong set point, but I cannot get an endo to even understand my argument. If my TSH is just above the minimum in-range level then my FT4 and FT3 are scraping along at the minimum also which leaves me very ill.


ThyCa patients have to stop Levothyroxine for 4 weeks and Liothyronine for 2 weeks prior to RAI to enable TSH to rise to >30. I've no idea how long you would have to stop T3 if you continue taking Levothyroxine. I've had 3 Levothyroxine dose reductions in 2 years and TSH hasn't budged from <0.01 although FT4 and FT3 dropped considerably. TSH set points can be reset so it might be necessary to stop medication altogether to trigger a rise in TSH.

If someone is able to stop T3 for 2 weeks surely it suggests they don't need the T3?

AndiRiley profile image
AndiRiley in reply to Clutter

This lady accepts that she will indeed be very ill for several weeks every six months. A hard price to pay, hence my interest in seeing if it is necessary.

shaws profile image
shawsAdministrator in reply to AndiRiley

I would suggest to the Endocrinologist that instead of relying on the TSH - which is from the pituitary gland that he goes by a Free T4 and Free T3 blood test which may pin-point more accurately of whether or not the patient is hypo or hyper (too much hormones or too little).


**Please note, the half-life of the medications may vary per person, so some people may have a falsely suppressed TSH, even at the euthyroid state, when taking T3 containing medications.

This is when free T3 and T4 testing will come in handy, as well as of course, looking out for symptoms of hypo- or hyperthyroidism.

Maybe send to the Endo the following studies:-

That's a good document. Thank you. I wish I could nail my endo's feet to the floor, pin his eyes wide and make him read it. Unfortunately the "closed mind" would still be an issue, because he already knows everything there is to know.

shaws profile image
shawsAdministrator in reply to AndiRiley

Until he or his wife become hypo and don't improve on levo. In fact they might even be worse on it so I'm sure he would learn the hard way that levo isn't perfect for all.

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