Nearly 10 years ago, the American Association of Clinical Endocrinologists recommended that the range for TSH be changed to 0.3-3.0. Labs have not kept up with the recommendation; therefore, when doctors look at your labs and see a range of, something like, 0.4-4.5, your 3.94 is right in range.
http://thyroid.about.com/cs/testsforthyroid/a/newrange.htm
"The new guidelines narrowed the range for acceptable thyroid function, and the AACE was encouraging doctors to consider thyroid treatment for patients who test outside the target TSH reference range of 0.3 to 3.0, a far narrower range. AACE believed that use of the new range would result in proper diagnosis for millions of Americans who suffer from a mild thyroid disorder, but have gone untreated"
"According to the National Academy of Clinical Biochemistry, more than 95 percent of normal, healthy people have a TSH level below 2.5mU/L. Anyone with a higher level is likely to have underlying Hashimoto's thyroiditis or another thyroid disease which has not progressed to full blow hypothyroidism.
This fact is backed up studing TSH levels in African Americans. This population has a very low incidence of Hashimoto's thyroiditis and has an average TSH level of 1.18mIU/L."
Excerpt from page 74: "Your Thyroid Problems Solved" by Dr Sandra Cabot and Margaret Jasinska ND. A good book i bought it for a $1 at a booksale. Bargain. :) Check out the article: "The TSH Reference Range Wars: What's "Normal?", Who is Wrong, Who is Right" by Mary Shalom.