Thyroid UK
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Blood test results on T4/T3 combo, advice please

HI I would welcome some advice on interpreting recent results. I am on T4 (75mcg on 4 days per week and 50 on three days) and 10 mcg of T3 daily, in 2 doses. I did not take T4 before test but had the T3 the evening before.

TSH - 0.17 (range 0.27 - 4.20)

Free T4 - 11.4 (range 12-22)

Free T3 - 3.76 (range 3.1 - 6.8)

Just before this I was on 100 mcg of T4 only. TSH was slightly suppressed. T3 was about the same as it is now.

T4 seems very low now. Is the T3 result an accurate reflection of circulating T3, given the time since last dose? This seems low now.

I am feeling tired and not sure whether to take more of something. I will go back to endo but he is concerned about TSH as I had atrial fibrillation before (I was on higher dose of T4 before, with the T3). My free T3 was higher then. When I was recently on T4 only I felt okay but cold and tired. I am obviously converting T4 to some extent but perhaps not very well - what's the best approach? Help!

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You are under medicated because your FT4 is below range and your FT3 is low in range despite taking T3. If you left 12 hours between last T3 dose and blood test you can probably extrapolate FT3 result by +10% to 4.1 which I think is still low. Increasing either Levothyroxine or T3 dose will suppress your TSH.

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