Instructions Before Taking a Thyroid Function Test

The thyroid gland consists of two lobes. It's in the front of your neck, below your voice box. The thyroid helps maintain body temperature and heart rate and also affects your energy level.

When the thyroid is not functioning properly, we might experience symptoms such as feeling hot or cold, constipation, dry skin, and weight gain.

Thyroid function tests to diagnose your condition will go more smoothly with some simple preparation tips.

Preparation Before Blood Test

• Many people experience anxiety before a blood test, but following a few simple steps can calm your nerves.

  Moisturize dry skin from the hand to the elbow to ease the pain of the needle. Apply moisturizer after bathing or washing dishes, or any other time your hands are wet.

  If the phlebotomist finds a vein but the blood doesn't flow into the tube, you might be dehydrated. Starting a few days before your appointment, drink at least eight glasses of water a day to make the veins more prominent and to promote easier blood flow.

  When the body is warm, blood circulates better and is easier to draw, according to Harvard Medical School. Keep your coat or sweater on while you're waiting to be called, and let your arm dangle by your side to increase blood pressure in the veins.

  If you feel you're going to faint, tell the phlebotomist before your blood test, and she can draw your blood while you're lying down.

TSH Test

• A TSH test is the most common blood test for measuring the function of the thyroid gland. If your TSH level is too low, your thyroid gland is producing too much thyroid hormone. High levels of TSH signal that the thyroid is not producing enough hormone.

Before Radioactive Iodine Uptake Scan

• Tell your doctor if you are pregnant or breastfeeding, because radioactive iodine could harm your fetus or nursing baby.

  Taking thyroid hormones or eating shellfish that contain iodine might affect the test results. So starting about a week before your thyroid scan, you might be asked to avoid those.

  On the morning of the test, you'll be given radioactive iodine in pill form. You need to wait at least four to six hours for the radioactive iodine to reach the thyroid, before your scan.