thyroid and diabetes

Hi, I have type 2 diabetes and don't make enough thyroid.  I had labs done that came back in the normal range but my doctor still upped my medication.  I take levothroxin 50mcg 1xday and she upped it to 100mcg 1xday.  My question is why would I need more if test were in normal range?  TSH was 4.205 Triiodothyronine,free serum 3.4 and Thyroxine free direct {t4} 1.25

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My guess would be because your TSH is a little higher than the Doctor wants it to be.
Recent studies have shown that TSH is better with levels between 1.0 - 2.0.
As your Doctor why?