Thyroid UK
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Help with blood results please!

I have just had a blood test and managed - at last - to get my Free T3 tested! I would appreciate some help in interpreting the results. I have been on T3+T4 (Nature Throid) since December (after stopping Levothyroxine). I take sub-lingual B12 and a daily multivitamin. I stopped my Nature Throid 36 hours before my morning test (ie missed 3 doses).

B12 463 (180-2000 ng/L

Serum Folate 16 (2.8-20 ug/L

Ferritin 151 (20-300 ug/L)

TSH 0.04 (0.2-4.5 mU/L

Free T4 9 (9-21 pmol/L) It was 14 a year ago

Free T3 3.6 (2.6-6.2 pmol/L)

Vit D is listed 'to follow' but as previously been ok.

I suppose the thing I am most worried about is that the Free T4 reading has gone down so much - to what it was for years in fact - but maybe that is because I am now on Nature Throid rather than Levothyroxine. Any help would be appreciated.

2 Replies

Stiltski, 24 hours is ample time to leave between last dose and blood draw.

If you extrapolate FT3 by +30% as your last dose was 36 hours before blood draw, I estimate your normal circulating FT3 is around 4.68 which is just shy of the top third of range considered ideal. TSH is low as expected because of the T3 in NDT and I've observed that FT4 is often lower on T3 or NDT than it is on Levothyroxine. It may be that the oral T3 in NDT means less FT4 is required for conversion and also that oral T3 can stimulate the conversion of T4 to T3 too.

B12 <500 can cause neurological symptoms so most here supplement to get B12 high in range. I'd increase your dose and take a B Complex vitamin to keep the other B vits balanced.

Ferritin and folate are optimal.


That is really helpful. Thank you very much.


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