This Blood Spot Test is for The T4 Hormone (Thyroxine) ONLY
Total T4 and free T4 are two separate tests that can help a doctor evaluate thyroid function. The total T4 test has been used for many years to help diagnose hyperthyroidism and hypothyroidism. It is a useful test but can be affected by the amount of protein available in the blood to bind to the hormone. The free T4 test is a newer test that is not affected by protein levels. Since free T4 is the active form of thyroxine, the free T4 test is thought by many to be a more accurate reflection of thyroid hormone function and, in most cases, its use has replaced that of the total T4 test.
Collect sample in the morning within 30 minutes of waking, and before eating or drinking anything (except water).
1.Tape filter card flat (below waist level) with flap hanging
down and away from collection filter strip (note: back of flap
should not be touching filter strip).
2. Open the alcohol prep pad and sterile gauze.
3. Select finger (middle or ring finger of non-dominant hand is best).
4. Wipe finger with alcohol prep pad & allow to dry for 15-30 seconds.
5. Twist cap off lancet and press small white section firmly against the side
of finger tip until lancet clicks.
6. Quickly wipe away the first blood drop with the sterile gauze pad.
7. Position finger over circle of blood spot card and gently milk (don’t
squeeze) blood from the finger.
8. As blood drop forms and is ready to fall, touch it to the center of the
circle (one drop per circle); continue collection until all circles have
9. When finished, blot finger with gauze then apply bandage.
10. Leave blood spot card open to dry - minimum 30 minutes.
11. Once blood sample is dry, close flap and place in the plastic box.
TIPS: Collect so that your hand is below your waist, allowing gravity to
assist with blood flow.
To encourage blood flow before nicking finger, rub hands together/swing
arm and/or run hand under warm water.
About Thyroid: Dr. Theirry Hertoghe explains the difference between T3 and T4 in the following video.
Dr. Delgado and Dr. Sangeeta Pati talk more about thyroid here.