How Much Is TSH Affected By Testing Blood Drawn 2 Hours After Taking Thyroid Medication?

Posted on Fri, 31 Jul 2020

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Fri, 31 Jul 2020 Answered on

Thu, 7 Aug 2025 Last reviewed on

Question : How much is TSH affected by testing blood drawn 2 hours after taking thyroid medication?

Answered by Dr. Dr. Elona (1 hour later)

Brief Answer:
It is not affected.

Detailed Answer:
Hello,
I have gone Through your query and understood your concern.

TSH is a pituitary hormone that responds to the circulating thyroid hormones. For the patients that take thyroid medication (Levothyroxine), the TSH level is necessary to adjust the dosage of Levothyroxine.

Taking a T4 medication the morning before your lab test will not be an issue, because it will not affect the TSH result.

You will get an accurate representation of your TSH value whether or not you take your T4 medication before a lab test.

So, don't worry

Hope I have clarified your doubts.
Best regards

Above answer was peer-reviewed by : Dr. Arnab Banerjee