I am on 25 mcg levothyroxine.does the medicine affect the thyroid blood test level? should i skip the dose of levothyroxin the day of blood test?

Take your Rx: The test is largely about how well the medicine is working.

Yes, No.: Yes the medicine changes the level of the blood test. That is why you are taking it, because your thyroid has tested as under-active. It takes about 6 weeks for your blood test to reflect the impact of your medication so, no, not taking the medicine on the day of a test will not effect the test one way or the other.