free T3 blood test and reference ranges

Free T3 is the active type of the thyroid hormones in your body. Thyroid gland produces 2 thyroid hormones as T3- triiodothyronine and T4-thyroxine. Thyroid gland produces thyroid hormones by the effect of another hormone TSH- thyroid stimulating hormone which is secreted by pituitary gland.

Thyroid hormone- T3 has 2 forms as free T3 and bound T3 which is bound to proteins. Free T3 is the active thyroid hormone in body for this reason T4 is transformed to T3 for body usage.

Preparation for T3 blood test

free t3 blood test tube

  • Fasting is not necessary for T3 blood test but your blood sample may be more clear if you fast for 8-10 hours before T3 test
  • You can have free T3 (fT3) blood test at any time of the day
  • Please inform your doctor about the medications you use
  • Some type of medications may affect T3 blood test like; thyroid medicines, birth control pills, steroids
  • Don’t begin or stop using any medications without asking your doctor

T3 thyroid hormone test procedure

free t3 blood collection procedure

  • A tube of blood sample is needed for T3 test
  • Your blood will be drawn from a vein inside your elbow or on the back of your hand
  • Nurse/technician will tie an elastic band ( tourniquet) to see your veins easily
  • She/he will clean your skin with an antiseptic solution
  • A needle will be inserted to your vein
  • You may feel a little pain during blood collection process
  • 2-3 mL of blood will be collected into the test tube
  • Nurse/technician will untie the elastic band and put a piece of gauze or cotton to stop bleeeding
  • All blood collection process takes 1-2 minutes

Free T3 blood test reference ranges

T3 thyroid hormone blood test is done to evaluate your thyroid gland’s functions. Your doctor may request TSH and T4 tests at the same time to have detailed idea about your thyroid gland.

  • 0-3 days female                    1,4-5,4 pg/mL
  • 0-3 days male                       1,4-4,8 pg/mL
  • 4-29 days female                  1,5-5,0 pg/mL
  • 4-29 days male                     1,4-5,5 pg/mL
  • 1-11 months female             2,5-6,5 pg/mL
  • 1-11 months male                2,0-6,9 pg/mL
  • 1-5 years female                   3,0-6,0 pg/mL
  • 1-5 years male                      2,4-6,6 pg/mL
  • 6-10 years female                 2,7-6,2 pg/mL
  • 6,10 years male                    2,9-6,0 pg/mL
  • 11-15 years female               2,6-5,7 pg/mL
  • 11-15 years male                  3,1-5,9 pg/mL
  • 16-18 years female              2,8-5,2 pg/mL
  • 16-18 years male                 3,5-5,7 pg/mL
  • 19-99 years                           2,5-3,9 pg/mL




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