Thyroid UK
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Blood test results advice - on T3 only

I am on 40 mcg T3 daily and am seeing a consultant every 4 months. When I last saw her in January , I felt ok and my blood test results were FT3 5 (3.1-6.8) and TSH 0.18 (0.3-5) so she agreed for me to continue on 40 mcg. However, over the last two weeks (after a slightly busier week than usual) I started to feel extremely tired and low again so made an appointment to see a doctor who agreed to do another blood test in case there was another issue - tested cortisol, ferritin, iron, blood sugar, FT3 and TSH, Auto immune antibodies plus a few other things I believe. All came back ok except FT3 which was 19.5 and auto immune antibodies 295 (<100), TSH was 0.25. I don't usually take my T3 medication before a blood test but I didn't know she was going to test thyroid levels so I had taken 30 mcg two hours prior to the test. She has written to the consultant today for advice. In the meantime, does anyone have any idea what could have happened?! Can having taken T3 prior to blood test raise it so high? Thanks for any advice.

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Taking your T3 just 2 hours before the blood draw will most certainly have affected the result T3 peaks in the blood 2-6 hours after taking it. I think you might be asked to lower your dose, but I would suggest that you ask if you can repeat the test and make sure you take your last dose of T3 12 hours before the blood draw.

Of course, the raised antibodies confirm autoimmune thyroiditis aka Hashimoto's and as antibody activity causes fluctuations in levels it could very well be that you had very recently had an antibody attack and a hormone dump which contributed to the high result.

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