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Thyroid UK
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Help to advise on Med dosage

My lab test before taking Carbimazole:

FT4 = 29.2

FT3 = 10.4

TSH = < 0.015

Tgab = 1087

Tpoab = 1679

I started Carbimazole 10 mg daily from 1st June - 1st September. My blood test done on 1st September 2016 was:

FT4= 8.29 ( 9.0 - 19.0 pmol/L)

FT3= 2.67 ( 2.63 - 5.70 pmol/L)

TSH = 3.605 ( 0.350 - 4.940miu/L)

Doctor asked me to continue 10 mg of Carbimazole after the above test. The new test done on 29th September 2016 was:

FT4 = 8.78 (9.0 - 19.0 pmol/L)

TSH = 5.9625 (0.3500 - 4.940 miu/L)

(doctor only run these 2 tests to determine dosage adjustment). Based on this new test, doctor reduced carb dosage to 5 mg daily.

I am afraid that 5 mg carb may further reduce my FT4 as the new lab had shown that My FT4 has been low. Can anyone please help to advise how to make my hormone return to normal range again? Do I need to stop the carb for a few days or reduce the dosage to 2.5 mg daily? Does this test show that I am now permanent hypo? Thank you very much. Linda

2 Replies


FT4 should rise and TSH drop after reducing Carbimazole dose to 5mg. It's probably best to retest in 4 weeks to see what levels are on 5mg before reducing further.


Thank you clutter for your reply.


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