Doctors can diagnose disorders related to thyroid at an early stage. Your doctor will ask you about the symptoms and will ask about your medical history. Your doctor will ask you to go through the blood test as it will hem them diagnose the health conditions.
Blood tests can measure the level of the thyroid hormone thyroxine and the level of TSH. If the TSH level in the blood is high or thyroxine level in the blood is low, this indicates an underactive thyroid. This is because the pituitary gland of humans produces more Thyroid Stimulating Hormone to stimulate the thyroid gland to produce more thyroid hormone.
TSH test is the best screening test, this is the reason why doctors will ask you to check TSH level first and then if needed thyroxine level.
This test of TSH level in the blood helps doctors in determining the kind of dosage of medicine that a patient needs. This test also diagnoses a condition called subclinical hypothyroidism, which usually doesn't show any signs or symptoms.
You should also make your doctor aware of the certain medications that you were taking before the blood test, as it might hinder the final report.