It's probably best to wait until after the test before taking thyroxine otherwise you could get a false high result for your T4. If you are taking anything containing t3,such as Armour or liothyronine, you definitely should wait or you'll give your doctor a heart attack with your high t3 (unless you're on the show release liothyronine).
Good luck for the blood test. I hope it uncovers the reason for your symptoms.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.