Why is T3 required in a thyroid blood test if TSH and T4 are with in normal range. My doctor said it’s not need.
Importance of T3 testing: Why is T3 required in a... - Thyroid UK
Importance of T3 testing
Written by
Suffolklady
To view profiles and participate in discussions please or .
Read more about...
68 Replies
•
SeasideSusieRemembering
Suffolklady
Another doctor with blinkers on and showing his ignorance about thyroid.
T3 is the active hormone that every cell in our body needs.
T4 converts to T3.
Low T3 causes symptoms.
If we don't test FT3 at the same time as FT4 then we can't know how well (or not) we convert.
But if the F4 and TSH is in range then does this mean that the conversion is good. Think this is what my Drs is trying to tell me.
Your TSH is far too high ...at 3.1
healthunlocked.com/thyroidu...
Your Ft4 is high at 21 (12-22)
Did you take levothyroxine shortly before blood test?
Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .
Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)
Do you have Hashimoto’s?
For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12
Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies
Low vitamin levels result in very poor conversion of Ft4 to Ft3
Ask GP to test vitamin levels (and thyroid antibodies if not been tested yet)
Steroids may also affect thyroid significantly
Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies
thyroiduk.org.uk/tuk/testin...
For thyroid including antibodies and vitamins
Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random
If you can get GP to test vitamins and antibodies then cheapest option for just TSH, FT4 and FT3 £29 (via NHS private service )
monitormyhealth.org.uk/thyr...
If antibodies are high this is Hashimoto's, (also known by medics here in UK more commonly as autoimmune thyroid disease).
About 90% of all primary hypothyroidism in Uk is due to Hashimoto's.
It’s difficult to argue with a doctor. Yes my THS is high never been under 18 usually 20-22 and my T4 was 0.82 in January last time where as two months before it was 3.1. It’s a mystery to me why it goes up and down and the wide range of ‘normal’ in results.
I didn’t take my levathyrixine near my test but left it over 24 hours. I was on a fasting test too
Sorry got that wrong T4 is in the 20s and TSH varies from 0.82 and 3.1
You may not realise that you can edit, or delete, any posts or responses you have made here.
HealthUnlocked have produced some help for how to do this. You can find this here:
support.healthunlocked.com/...
When you edit the original post in a thread, you will also have the option to add (or remove) a single image. (To replace an image, remove the existing image, then add the new one.) This is the same process as writing a new post:
support.healthunlocked.com/...
I am pointing this out purely to ensure that you know your options. 
(If you make extensive changes, it is sometimes helpful to add a comment so that people can see that you have made changes.)
Thank you very much for your advice, much appreciated
How much levothyroxine are you currently taking?
50mcg levothyroxine is only a starter dose
The aim of Levothyroxine is to increase the dose slowly in 25mcg steps upwards until TSH is under 2 (many need TSH significantly under one) and most important is that FT4 is in top third of range and FT3 at least half way through range
NHS guidelines on Levothyroxine including that most patients eventually need somewhere between 100mcg and 200mcg Levothyroxine.
nhs.uk/medicines/levothyrox...
Also what foods to avoid (eg recommended to avoid calcium rich foods at least four hours from taking Levo)
NICE guidelines
cks.nice.org.uk/hypothyroid...
The initial recommended dose is:
For most people: 50–100 micrograms once daily, preferably taken at least 30 minutes before breakfast, caffeine-containing liquids (such as coffee or tea), or other drugs.
This should be adjusted in increments of 25–50 micrograms every 3–4 weeks according to response. The usual maintenance dose is 100–200 micrograms once daily.
Essential to test TPO and TG antibodies at least once and vitamins at least annually. Vitamins frequently need supplementing to maintain optimal levels
I am on 25mg levothyroxine
How long on 25mcg?
If over 65 starting on 25mcg ....but dose should be increased steadily, just same as patients under 65, who start on 50mcg
Bloods should be retested 6-8 weeks after each dose increase
New NICE guidelines
nice.org.uk/guidance/ng145/...
1.3.6
Consider starting levothyroxine at a dosage of 1.6 micrograms per kilogram of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 with primary hypothyroidism and no history of cardiovascular disease.
BMJ also clear on dose required
Post re getting dose increased
Where do you get vitamins tested? Which one's are co factors for levo?
Gps in Liverpool have been stopped from testing for T3. This is annoying the hellout of me as there is now a 4 mtg wait just to get an appointment for clinic which is lumped in with diabetic clinic.
If you’re feeling good then it doesn’t matter.
If not and you have symptoms, then maybe your conversion isn’t that good. The point is that you just don’t know if you don’t test FT3.(See Seaside Susie’s explanation above).
How do you feel?
Suffolklady
But if the F4 and TSH is in range then does this mean that the conversion is good.
Definitely not. You can't possibly know how well you convert if you don't test FT4 and FT3 at the same time. If you don't test FT3 you don't know how much you are producing.
TSH isn't a thyroid hormone anyway, it's a signal from the pituitary to make thyroid hormone if the pituitary detects there's not enough. FT4 and FT3 are the thyroid hormones.
I've just rung healthwatch and nobody knows it's been stopped. Ccg are ringing back. Nice guidelines are that Gps were to be given extra training on interpretation of the results. So I've asked the question why who and what was the clinical reasoning.
No it does not mean the conversion is good. I have spent 4 years feeling awful with TSH and FT4 in range but because they do not test the FT3 I did not know that it was too low. The medics kept telling me I was fine.
FT4 only measures the T4 available for conversion. It does not indicate how efficiently your body is converting it. Only FT3 will tell you that.
My TSH was 0.19 (0.55 - 4.78)
My FT4 was 19 (10 - 25)
With these results the doctor would want to reduce my levo from 100mcg as the TSH is suppressed.
My FT3 result was 4.5(4.0 -7.0)
My FT4 was 60% through its range
My FT3 was 16% through its range.
So somewhere along the line T4 was not being converted into T3 otherwise the results would have been more balanced through there ranges.
Hope this helps.
That does help. Thank you. What about the antibodies test as well are these necessary
They are initially so you know what condition you have. That helps so you can realise for example if you are having a hashis swing. Or can confirm Graves disease. Continually testing antibodies though will not tell you anything new.
So if I ask once that should be enough?
Yes in my opinion. You need to know if you have hashis. If hashis is confirmed then you will know what to expect as symptoms.
And this one from this evening
It is perfectly possible for the pituitary to react to the levels of T4 and T3 such that all appears well. The pituitary will reduce TSH production (if high). So we can see TSH within range - whilst the levels of T3 available to the rest of the body are too low.
not in my experience, no
Being a cynic, I would suggest that doctors are reluctant to test free T3 for a patient they are treating with levo, because if this was low (and showed a conversion problem) they would have to acknowledge that levo-only treatment wasn't working. And - largely because of the cost of lio in the UK - they really really don't want to do that if they can avoid it.
IMO it’s not the Drs refusing to test FT3, in general they have no idea what T3 is - it’s the hospital labs have been told not to test FT3 because of the consequences of finding low T3 in many patients. I told my Dr that I was going to try NDT and he asked me what that was !!
Well I've set the car amongst the pigeons because I've asked the question why carnt they. It's our health they are messing with it we are paying for private testing and it's showing the need for a t3 supplement then we are being mistreated and it's medical negligence mass action time. No other patients would take this .
Absolutely agree Algic , why don’t all mistreated thyroid sufferers get together and start a revolution 😃..... or even get some sort petition going to hand in to the powers that be. It’s definitely maltreatment , so many are suffering unnecessarily. It’s so frustrating that so many of our so call medics are are so misinformed.
So far it seems to be the labs that have instigated this. But I'm waiting for a formal explanation with clinical evidence to justify. Nice are saying the opposite in fact advocating more education for GPs.
Well today was a complete let down. When I mentioned that for me to have a thyroid storm so bad that I was still experiencing symptoms so it must be fault in the loop. She looks at a 2yr old MRI and says it was fine then! Well that's no indication the pituatory is fine now. So sends me off to have the same tests that Gp used to be able to order plus cortisone. So the previously £1 test has now cost over £160 to the nhs. Gp could have done these tests and sent the results then they could have decided.
SlowDragonAdministrator
Prednisone is a glucocorticoid steroid
Glucocorticoids lower TSH
theinvisiblehypothyroidism....
Along with the side effects, prednisone being a corticosteroid can make conversion of T4 to T3 (the form of thyroid hormone that your body more readily can use) much more difficult and even suppress it when you are on high enough amounts. This will actually send your thyroid levels DOWN towards more hypo. A good endocrinologist will know that testing your thyroid levels too soon after or during a round of prednisone will drastically affect your numbers.
ncbi.nlm.nih.gov/pmc/articl...
ncbi.nlm.nih.gov/pubmed/203...
thyroiduk.org.uk/tuk/treatm...
I found that very interesting. I am on Predisolone 6mg have been on it for 3 years but no higher than 15mg.
Then you need referral to a thyroid specialist endocrinologist......TSH should not be used as tool for deciding dose of levothyroxine at best of times....obviously even more unreliable than normal if on steroids
Strongly recommend getting vitamins, thyroid antibodies and TSH, Ft4 and Ft3 tested ......via Medichecks if GP unhelpful
I have an endocrinologist he saw the results and again said do not need T3 all was fine
Vast majority of endocrinologists are diabetes specialists and have little understanding of thyroid
That is true
Hi, please clarify this for me. Does this mean when we’re on/have just finished a course of Prednisone, the TSH result would be a higher number?
Suspect the reverse....but I don’t have personal experience
TSH is always unreliable on any levothyroxine anyway
So what was the answer. Did they sort it?
Omg poor you. I’m sure they use us as guinea pigs. I sort of know a bit but it’s knowing enough that you can fight back with a doctor and not look an idiot.
Mines heard of it for sure but goes by the two results TSH and T4 as the T4 is in range I must be converting the F3 so he says if I wasn’t converting then the readings would show it. Simple! I’m due for a blood test in the next week so I’m going to ask.
So we have a perfect storm of can't - won't - you don't need it anyway ... it's a wonder so many of us are still moving really!
Thanks for the confidence boost.
TSH is secreted by the Pituitary Gland to tell the Thyroid to produce T4. This is an inactive hormone doing very little in the body.
It converts into the ACTIVE hormone T3 - which is needed in every cell of the body for healthy functioning. The brain has first call followed by the gut/immune system and so on. So if your T3 is low then there simply is not enough to nourish the trillions and trillions of cells and things begin to go wrong.
The T3 test result is very important for knowing the full story. Doubtful the lab will test unless your GP insists. The test is under £1 so offer to pay for it - so it's not cost ...
Am afraid your GP is bluffing or not up to speed.
I see you joined here two years ago so reading the posts on a regular basis you will know that Thyroid knowledge is sadly lacking at GP level and beyond ..
So what if you had good t4 and t3 but high tsh? What does that mean? Just interested
Has that happened to you ? In all the years I have been reading here I have not seen results posted as you suggest. The Pituitary normally responds to good levels of T3 circulating in the blood so if the TSH remains high then it may suggest a Pituitary issue ...
Was just curious as my recent results show i need increase, my tsh has gone from 3.99 to 4.3 in six weeks on same dose of 50mcg but my t4 actually increased from 14 to 16 and my t3 is 4.5 atm, range being 3.5 - 6.5, im feeling ok and just scared if i increase my heart rate will get higher again, its still too high but not as high as it was on 75mcg, i also just had the short cortisol test the one where they inject you with hormone, these results showed my adrenal and pituitary were responding , my morning cortisol had also improved from 200 to around 330 which i was happy with?
If you have Hashimotos it is possible for results to fluctuate. Also there is not a huge difference between the two TSH results.
Heart rate is often linked to thyroid hormones. How are your levels of Folate - Ferritin - B12 and VitD ? - they all need to be optimal for your hormones to work well and for the heart. Do you take Magnesium ?
Iron was ok recently its actually back to where it was before i had b12 injections in early 2019, as it halved after them, i do however need to retest mag and pottasium as these have not been done in awhile vit d was 74 last test and b12 was still ok, i dont take any supplements
No point in testing Magnesium as the blood naturally keeps levels tight by drawing magnesium from bones. Range also very small.
Are you taking a good B Complex to keep all the B's in balance ? Not sure that Iron levels are connected to your B12. Are you still havi g injections.
What was your Folate level and your VitD ?
Do you have T3 tested ?
Some people have a single nucleotide polymorphism that inhibits their ability to convert t4 to t3. This is my case. Even though my T4 is high, TSH is low my T3 was very low, my ignorant endo stated that T3 isn’t a good indicator because it is created in demand at the tissue level. Which isn’t the case for all. DIO2 SNP
My GP said he didn't know much about T3..........he's only been treating my underactive thyroid for 18 years !🙆🏼.........10 of those years on 50mcgs T4 !!!😱
My endocrinologist said T3 was irrelevant last time I saw him. I was previously impressed by him but the first time I saw him was privately, since then it has been on the NHS where he's been great the time before last, suggesting I could be put on a trial of T3 if the levo wasn't working, but last time he was in full NHS mode and said T3 was irrelevant. I think they are pressured every so often (more often than not) into keeping costs down. The system is rotten.
Hi Scrumbler, just wondering why you felt ill with a high t4 (out of range)? I was under the impression that was ok as long as t3 was in range. How did it make you feel?
Testing T3 is probably even more important than the T4. Even if your T4 levels are normal, your T4 might not be converting to T3, which would make you feel symptoms of hypothyroidism.
That’s entirely possible.
Does a sudden high pulse rate and heavy legs indicate a change?
High pulse rate frequently due to being under medicated
As you have been left on half the standard starter dose of levothyroxine that’s hardly surprising
Levothyroxine doesn’t “top up” your own thyroid hormone output, it replaces it.
If we have been hypothyroid a long time, we may need to start on low dose, but it should still be increased in 25mcg steps upwards as quickly as we can tolerate. Bloods retested 6-8 weeks after each dose increase
Most people need somewhere around 1.6mcg levothyroxine per like of their weight. So if you weight 9st 10lb that’s approx 61.6g x 1.6 = 98mcg levothyroxine per day.
I think you may have transposed the stones and pounds for your calculation, if you do not mind me saying so?.
My online conversion chart would make 68kg the same as 10lb 9st. Nine stone ten pounds converts to 61.6886kg.
Just saying ...
Sorry yes ...just corrected now
shawsAdministrator
That's the usual response from someone who is ignorant of the purpose of T3.
Same here. I’ve been on Levo 6-8 weeks and due to have retest of bloods done. I said I need t4 and t3 and she refused! I was diagnosed hashimotos and they said ‘your levels are normal we don’t need to start anything.’ I pointed out they’re in fact not normal and i can’t have ivf until at least my tsh is optimal so they put me on 25mg levo.
Hmm, I’m currently looking at the NICE guidelines. It says to test for T4 if TSH is above range, and only T3 if tsh is below range. Why?!
The primary reason seems to be to save money!
The secondary reason is that the medical establishment rather takes for granted that in someone who is hypothyroid, all they need to know is their TSH - and FT4 to confirm it.
There is zero acceptance that anyone could be suffering from poor conversion of T4 into T3.
There is nearly zero recognition that in people who have a failing thyroid, the body regards T3 level as imperative and tries to keep that level adequate even as the person's thyroid deteriorates. In such people, TSH might not be very high, FT4 might be low but possibly not below bottom of range. And that can continue for a long time.
There is zero recognition that having the set of TSH, FT4 and FT3 from when someone was healthy could be helpful in deciding on thyroid hormone dosages.
However, they do recognise that if TSH is low, FT3 could be high or very high. That is life-threatening in the short-term hence they need to test and check.
In my book, the three tests should always be performed in parallel - never one without the other two.
That's interesting. I have read on here and the Prof Toft article that over range t4 was perfectly fine as long as t3 in range. I have out of range t4 and have always argued with my doctor that that was fine and gave him articles that backed it up. I'm now wondering whether I should be concerned.
I think Prof Toft was arguing that an FT4 which was just above the upper end of the range was all right if the FT3 was unequivocally normal. On the other hand, it sounds as if Scrumbler's FT4 was *way* out of range.
I had that issue of T-shirt & t4 (somewhat) normal. But in the afternoon I was still feeling like My t4 was way low. The t3 test showed I was a bit low. T3burns hot & fast(6hour half life). I started taking it about it with my t4. I did feel better. Then after about 6 months I noticed I was still really tired in the afternoon. My endo added a second t3 about 12:30pm, wait an hour to eat & now I am much better the rest of the day. I still go to bed early.
I would say Most of all these adjustments are based on how you feel, then the test results. When my t3 was added my t4 was dropped a lot: from 187 to 135mcg
Not what you're looking for?
You may also like...
Importance of testing before taking supplements
Just had my vit D blood result . 160mnol/l.
Range 50.0- 120.0
Been taking 5000 supplement for...
Testing of reverse T3.
Could someone tell me the importance of testing reverse T3 please. I've never had it rested and...
T3 testing
Hi I need to order a test to measure my T3 levels as my practice doesn't include this in their...
T3 testing
What do people think about lobbying Nice and CCGs regards this arbitrary stopping of T3 testing?...
The importance of T4 and T3
Another question for you @[80578], hope you don't mind. I saw in my son's Physiology book last...
Reverse T3 testing?
The importance of tea
Private T3 testing?
