Triiodothyronine - Free - FT3 (Serum) During Pregnancy

Laboratory Tests

Obie Editorial Team

What is Free Triiodothyronine?
Free Triiodothyronine or FT3 is part of the thyroid panel of blood tests. This test is ordered alongside the TSH and T4 test if a patient is suspected of having an overactive thyroid or as a follow-up test when a patient’s TSH and T4 tests return abnormal results. Symptoms of an overactive thyroid may include weight loss, diarrhea, elevated heart rate and anxiety.

Conditions that can affect FT3 levels include Grave’s disease and certain autoimmune disorders.

Normal Value Range

  • Negative Pregnancy Adult: 2.4 to 4.2 pg/mL or 3.7 to 6.5 pmol/L
  • Pregnancy Trimester One: 4.1 to 4.4 pg/mL or 6.3 to 6.8 pmol/L
  • Pregnancy Trimester Two: 4.0 to 4.2 pg/mL or 6.2 to 6.5 pmol/L
  • Pregnancy Trimester Three: *No reported values for pg/mL or pmol/L