Thyroid UK
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Please help me decipher my latest blood tests.... T4 and T3 not what I expected at all

These are my most recent results:

Date FT4 TSH FT3 Dose

28/01/201323.7(1123) 1.72(0.355.5)4.6(4.48.8) 100/125


05/03/201327.4(1123)0.17(0.355.5)(4.48.8)125 Daily



Last result (29/4) was taken after I spent 2 weeks in the heat of Turkey. I have always shown an improvement in symptoms in hot countries but this is the first time I've actually managed to get a blood test done since I realized this improvement in symptoms was temperature related. I was doing 2 weeks of watersports for about 6-8 hours/day so not exactly a restful holiday in the slightest! I've spent all this week exhausted and now have symptoms of a cold and feel pretty rotten. I was hoping for a lower T4 (possibly not this low) and a higher T3. Yes it's higher than last time. Maybe I needed longer in the heat for better results?

My FT3 has never been this high before. Often it's below range. The gaps are because the hospital lab does it's own thing despite FT3 being requested. Both the last 2 times we've had to call up and ask for them test for it. IDEALLY I think my FT3 needs to be mid-range at least; either through a higher dose of thyroxine or combined T4/T3 if I can get it.

Why has my FT4 suddenly dropped off? Does this mean I am undertreated still with Thyroxine? Should I give 125 daily another chance? Is this related to better conversion? I'm HOPING to get FT3 at my specialist appt next week.This is the LOWEST FT4 I have on record except for when I was first diagnosed and it was 9.4 with a TSH of 33 (They never did FT3). This is also the second time ONLY that my FT4 has been within range (it's usually 22+). I've been complaining of symptoms since I've been on Thyroxine (March 2011). I've been on all three doses listed before but they always put me back because my FT4 is "too high".

I believe when on a higher dose you get an initial spike in FT4 as the body gets used to it then it drops off - I'd like to know if anyone else has had this at all?

2 Replies

Hi Very good info but what dose of what are you on crucial.? The hear would be vit D , hormonal, strongly effects the thyroid. I should have a test to see if ow, huge range anyway. You could ell need some but essential if low to fits have a test for corrected calcium as calcium must always be in range and D pushes it up. Should ideally be under an Endo, really complicated, other consultants are only allowed to diagnose it ,not treat it. If no Endo Gp has to do!Your Ft3, on treatment normally needs to be near the top and T4 top third, but depends how you feel and this is is only on treatment. often ( not in your cae0 you need a little less T4 and some T3 on a script. This is Endo`s preferred option for Hypo.If variable on the correct treatment ,it is often Graves, but Graves is uncommon.It usually takes about a year with slow increases in drugs according to bloods and how you feel to be stable, can be longer. Make sure you have had the other tests as stated,D but also B12 and Foliates, autoimmune and hormonal, diabetes ditto and Ferritin iron, often too low.

I hope this helps Not sure if you are seeing an Endo, at the moment if not happy research your self, then ask for a referral The body often does improve,& bloods too on treatment , then drops off and increase in drugs needed, this is until all OK.

Best Wishes,


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Hi Jackie - Doses are written next to the test results (last column) and I'm on 125/125/100 currently which is ~117mcg.

I've had all the others done and they were fine, my B12 was over the high end but I'm not worried as I eat a lot of meat, fish even though I don't supplement and it's also in Whey Protein which I take a lot of as I function better on a high protein diet. I supplement with Vit D and try and get outside as much as possible when the sun is out.

I think my FT4 is low because my body started converting properly in the extra warmth/heat BUT I would have expected the FT3 to have been higher with such a drop off - i just can't seem to get it above the middle range. I'm confused as to whether the drop off in T4 means I can take more which will up my FT3 as before or whether my current dose is adequate to have T3 added. I could feel better I know that for sure. I saw an increase in T3 with an increase in T4 to 125 daily.

I'm in between endos as have little success with them! Seeing a new one on Tuesday. My doctor is great though - it's taken a while to establish a good working relationship but we're getting there slowly.


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