Meals generally do not affect the level of thyroid hormones in the blood, and it is generally permissible to eat before the test, but try to fast as much as possible so as not to test other items that require fasting. Thyroid function is usually checked in the laboratory through blood sampling, mainly including thyroid hormone and thyroid stimulating hormone levels, whose levels are generally not affected by diet, therefore, normal people do not need to fast during routine medical checkups. If you also need to check the liver function, abdominal ultrasound and other items that require fasting, you still need to have a fasting test. In conclusion, before undergoing a thyroid function test, you should strictly follow your doctor’s instructions.