What are ormal ranges for thyroid levels?
…. The normal range for free T4 levels is about 0.7 to 1.9 mcg per ml; for free T3, the normal range is about 2.3 to 4.0 mcg per ml. The normal range for free thyroid levels is divided into four quarters, which are called quartiles. If the free T4 level is either low or in the bottom quartile of the normal range, he prefers to use thyroxine first and then add triiodothyronine later if they don’t show improvement. If, however, the free T4 is in the second quartile or above, he will initiate treatment with triiodothyronine only. “I generally find that most patients ultimately need both,” Johnson says. The doses he usually finds helpful are between 5 mg to 25 mcg of triiodothyronine and between 50 mcg and 250 mcg of thyroxine. …. Reference Bunevicius R, Kazanavicius G, Zalinkevicius R, et al.: Effects of thyroxine as compared with thyroxine plus triiodothyronine in patients with hypothyroidism. New England Journal of Medicine 1999; 340:4244-429. Cooke RG, Joffe RT, Levitt AJ:T3 augmen
