Article discusses how fasting and time of day of testing can alter TSH results.
...The Thyroid Manager online textbook mentions that Serum T4 concentrations peak 2 to 4 hours after an oral dose and remain above normal for approximately 6 hours in patients receiving daily replacement therapy.
For this reason, thyroid expert Richard Shames, MD has the following recommendation:
I absolutely recommend that patients have any morning blood tests evaluating the thyroid before taking any thyroid medication. I have always told my patients to do it this way.
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