What does a low FT4 mean ??: Hi , I have been on... - Thyroid UK

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What does a low FT4 mean ??

Ozzyfudge profile image

Hi , I have been on a 3 month trial of Armour Thyroid 1 grain (60) a day I was on Levothyroxine 75 before the trial … I have just received my blood results could someone please tell me would having low FT4 10.1 cause tiredness and a feeling of air hunger I’m always trying to take a deep breath but fail each time …

My results are :

TSH —1.42 Range ( 0.27-4.2 mU/L

FT4–10.1. Range (12-22pmol/L)

FT3— 4.2. Range ( 3.1-6.8 pmol/L)

One thing that has been great is that most of my

Pains in my body have gone but the tiredness and feeling of more enough air in my body is getting me down .. thoughts please ?

13 Replies
SeasideSusie profile image


Presumably your FT4 has lowered since starting NDT?

When taking T3 in any form - be that in NDT or synthetic T3 - it tends to lower our FT4 level, it's just what it does. So if your FT4 has lowered since starting NDT that's normal.

However, looking at your results we can see that you are currently undermedicated. When on NDT one expects to see TSH low (even suppressed, again that is what taking T3 or NDT tends to do), FT4 lower in range than when on Levo only, and FT3 in the upper part of it's range when optimally medicated. So your TSH and FT3 may still have a way to go and suggest you're not yet on enough NDT.

Where we need our FT4 when on combination hormone replacement is a very individual thing. Some of us are fine with a low FT4, some of us need it higher in range. Personally I need mine more or less in balance with FT3 at around 70% through range. I'm on Levo plus T3 and your FT4 level would have me bedbound.

You are due an increase in your Armour dose.

Always remember that when doing thyroid tests the following is advised:

* Blood draw no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If looking for a diagnosis of hypothyroidism, an increase in dose of Levo or to avoid a reduction then we need the highest possible TSH

* Nothing to eat or drink except water before the blood draw. This is because eating can lower TSH and coffee can 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 and splitting the dose 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 phlebotomists or doctors

Hi Seaside Susie ! I always get a reply from you and I am grateful again for your help 🙏, yes I thought I needed more Medication I was put on 90 one and a half grains at the start of the trial but I felt strange so endo reduced it down … I am really pleased to be free of pain and my cholesterol has reduced and my vit D is 85 which is the best it’s been ! I take 4000vit d with K2 every day but the tiredness is dreadful they have just started me on CPAP also but I see it’s also linked with Hashimotos, I have had my 60 armour this morning I am going to take 30 at lunchtime to see if it may boost me a little .

I see the endo next Friday but I have to say I am better on it that Levothyroxine .

Thank you again x

SeasideSusie profile image
SeasideSusieAdministrator in reply to Ozzyfudge


As you didn't do well going straight onto 90mg Armour, it might be worth taking it slowly and maybe just add 1/4 grain rather than1/2 grain, see how that goes for 2 or 3 weeks, you can always add another 1/4 grain then. Sometimes slowly increasing is the better way to go.

Yes I think you are right it’s just hard trying to cut the pills they crumble ! Here are my results before I was put on armour T3 has gone down is that a good sign ? Appreciate your time Seaside susie thank you 🙏

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SeasideSusie profile image
SeasideSusieAdministrator in reply to Ozzyfudge


Here are my results before I was put on armour T3 has gone down is that a good sign ?

No, generally you're aiming for FT3 to be in the upper part of it's range, so with a range of 3.1-6.8 you may be looking at 5.8+

Hey there again :

Did you take bench mark readings of T3 and T4 before you started this trial of NDT ?

Has your T3 moved at all ?

It is usual for the T4 to go down when on NDT as it means it's being converted into T3 :

Some symptoms have been relieved, some have not, why have you stopped at 1 grain ?

I would suggest you increase your dose by 1/4 grain increments weekly, until you feel you have gone a " bit over " anxious, nervous, or just not as well as the previous week, and then drop back down to the previous weeks dose.

Stay on that dose for 6 - 8 weeks and then take a blood test to see where your T3 and T4 then sit.

If you get to 2 grains, hold that for 6 - 8 weeks and then take a blood test and see where you are and how you feel.

I seem ok on 1 + 1.2 grains of NDT - but we all different and we dose to the relief of symptoms not a blood test.

My TSH is 0.01 - no surprise there : my T3 at 110% and my T4 at 25 % and I am not hyper and run myself slightly hypo.

P.S. I 've just looked back and remined myself of your Hashimoto's AI disease diagnosis and the fact your have been put on HRT patches - have things improved since last post in the hot flushes department ?

Ozzyfudge profile image
Ozzyfudge in reply to pennyannie

Penny Annie forgot to add yes the T3 has gone down .

Hi !! Thank you for replying !These results were from end of Feb 2021 … I know I’m mot on enough I was put on 90

Armour thyroid for the trial

But it was too much I felt weird so I came on here and started at just 30 and then only a few weeks ago went up to 60, 1 grain a day , I will take extra at lunchtime today … could it be causing the feeling of not enough air in my body ? ( low FT4)

Appreciate your comments thank you 🙏

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pennyannie profile image
pennyannie in reply to Ozzyfudge

I'm not sure what I'm looking at here - can't see much of anything and February results hardly relevant now 6 months later :

I see a red blob against folate ?

I aim for a ferritin at around 100 ; folate at around 20 ; B12 active 75 ++ and vitamin D 100 :

Your T3 looks like 4-76 so your T3 has actually gone down - you need more thyroid hormone replacement.

Ozzyfudge profile image
Ozzyfudge in reply to pennyannie

Thank you pennyannie , yes it has gone down I will take an extra 1/4 today and slowly ramp it up , I have MTHFR and can’t take folate or B12 properly folate made me manic It was frightening… but I have started b12 drops that are mentholated so I am trying to see if I can tolerate I also have the folate drops but I’m a bit scared to try . Thank you for your reply 🙏x

pennyannie profile image
pennyannie in reply to Ozzyfudge

OK then - I read it's best to take any thyroid hormone replacement of an empty stomach, 1 hour before food or 2 hours after :

Personally I take mine at 3 in the morning so well away from everything and when my body wakes me up to go to the toilet.

NDT needs spacing out about, at least, I would think, about 12 hours between doses.

Hi Ozzyfudge,

I'm not on any medication as yet but I do have a low in range FT4 and recently a below range 10 (similar levels to yourself) over the last 7 or 8 months.

My symptoms are mostly tiredness sometimes feeling very drained much of the time. It's a strange, very overwhelming whole body tiredness.

I do suffer with breathlessness and am trying to increase my ferritin levels also, so as pennyannie has said try to increase your ferritin also.

Take care.

Ozzyfudge profile image
Ozzyfudge in reply to Hedgeree

Thank you 🙏 yes I thought about ferritin also will do that today ! X

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