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Thyroid UK
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Is a FT3 blood test meaningful on it's own?

I'm getting a [private hosp] Lyme test done tomorrow & at the same time thought to get Selenium [been at the brazils a few years] and T3 done at the same time.

I'm on 25ug Levo ,over a month ,and Dr already refuses to consider T3 testing later on,

Same old: TSH+T4 only.

I'm not feeling great on low dose [worse than before, energy wise + aches] and the choice is either to bump the Levo up,already refused for now -or stop the 'experiment' until I can get a specialist referral to suit.

The big ? is- Is FT3 at this point a waste of money? [What about Total T3?]

I feel it may show effects of meds by now- but I can't afford the meaningful RevT3 test -which would give me a FT3:RT3 ratio for assessing my progress better.

If I stop Levo now the chance is gone to see T3 level under the Levo regime- however imperfect it may be.

Only one FT3 test to hand, private (pre- treatment with 25 mcg Levo) 4.8 [4.0 -6.8]

TSH 4.84 [0.27-4.2]

FT4 12.9 [12-22]

11 Replies

Your t3 may have risen just a wee bit on the 25 levo but not enough to take it to even the middle of the range. Drs don't go by the t3 results just the tsh. even the t4 if just in range they think you are fine. I know I haven't answered your question but I think that to pay for a t3 test would be a waste of your money but it might make you feel that you are doing something and your dr just might pay attention to it but it will be in range even if it is at the bottom of the range so will probably do nothing. Sorry all that is a bit long winded but its the only way I could write it.

Jo xx


As you are aware, 25mcg is so low. Maybe you will begin to improve as your doctor increases your dose - at least every 4 to 6 weeks. You most certainly must feel dreadful on a dose of 25mcg - it's bad enough when you are on a higher dose but not yet at an optimum level.


25mcg is a starting dose and perhaps an increase will reduce your TSH and bump up your T4. If you are converting properly an increase in T3 should follow. It takes time for the T4 to get into the system and my doctor only usually tests again after 6 weeks and, yes, only TSH and T4 if TSH is out of range. I assume your doctor is refusing to up the levo because its too early, when are you due for a blood test a the surgery.


'Official' blood test in another month!

I think she's being ultra cautious as my BP is a bit volaltie on many meds.though fairly good right now- on 3 half dose diff.BP meds

When I started Levo it went up quite a lot on one dose so I left it a week and started on half dose for a week and then upped it to 25.

I wish I hadn't reported the fact and I could have been on a more useful dose by now!

Plus, I'm over 65, too.

I think the advice so far may be right and it is probaly going to show not a lot.

I suppose my thinking was if I'm on a bad tack with just T4 the T3 might actually have dropped as I feel worse. If it really isn't going to show that- then I shall think again.


When I started on 50mcg of T4, my fT3 level actually dropped and I was able to use this info later on to justify getting Armour/T3, so in my opinion it would be a useful test at this stage. xx


Thanks Clare- that's a good historical perspective. I will follow it up as I'd rather check the essentials right now for the money spent , though mineral status is important.

I'm non meaty- so hesitate over Armour but wouldn't rule it out in the final analysis.

I know I need an Endo in the NHS for T3 use & looking for a referral, soonish.

I think there's a T4/T3 synthetic- did you ever try and how are things now?


I think that there used to be a synthetic T3/T4 preparation called something like Thyrolar, but I don't think it is made any more, although could be wrong on this. I am much better on Armour, but it took a long time and I felt worse before feeling better - I have written a blog (called a post now I think) called the Armour Diaries, which have documented my experiences, both good and bad - but I'm not sure how to find it with the new site :D Will try and post a link if I can. xx


Is your current TSH 4.8? because if so you are underdosed. Toft (NHS/ BTA) and the American Association of Clinical Endocronologists (aace) state that the majority of thyroid patients feel better with a TSH below 3. I know you have your bp to think about but mine got better when i raised my dose (Im on Armour) There is info out there about hypoT cuasing high bp. Also my bp would sky rocket at the docs so i got a bp monitor at home and took my bp at different times of day and it was fine. The doc wanted to put me on blood pressure pills! I had a very bad case of white coat syndrome!

british-thyroid-association... you might find something in here.


May I ask why you are testing for lyme and which test is it? and where you are going and how much? Have been considering it myself though recently my health has improved immensely so not sure xo


TSH 4.8 was before treatment started last month. Next test 4 weeks off.

I've been doing BP at home for years. It's fairly stable now- but doesn't take to med changes well.

It seems that it shoots up when my body complains about the latest medication... but eventually settles down [if lucky]. I'm on 3 meds currently for it- 1/2 doses.Probably adrenal based, deep down!

I don't get white coat now- probably due to low thyroid :~/

On the Lyme thing- I had two bites-past few years, one came up over 2 weeks as a round rash -very like the classic Lyme. AntiBios cleared it -but a bit late in, for comfort.

I just found the test price was wrongly quoted and is really £150 [Blood, not CSF ]-so I pulled the whole event tm.[>£300]

I couldn't get a Cortisol profile- they take the 24 hrs all in one go.

I would have like to have seen FT3 [as discussed]- but on balance have to sit it out now- till the famous TSH & T4 mystery tour end of next month, via NHS.


Sorry, I missed out your Lyme question.

I've had at least two occasions where bad reactions to bites occured last 10 years. The one of note produced a red weal in a raised growing slowly pea sized rash on my finger. It lasted 2+ weeks till using antibios to clear. It looked very like a typical Lyme rash but not Bullseye version.

I have a pic of similar Lyme rash [tho larger] but can't post it directly here.

The private clinic misquoted my Lyme test price -so I cancelled it, as it had risen to £150.

On balance- though Lyme and HypoT can be confused by similar symptons I think I'll continue with the Levo and hope things improve.

I doubt if the likelihood of ongoing active bacilli is high- though it would have been good to check.

Maybe another time.


I gave up on taking Levo and finally got T3 trial and still progressing. Awaiting latest tests inc. RT3 :) [My cost -as NHS flunked it!]

T3 is fine for me andI've just done a cycle up to and down from 50mcgs!


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