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What is a Normal TSH?


Updated July 01, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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The "Old" Normal Range
While the majority of traditional doctors in the U.S. agree that the TSH test is their preferred way to diagnose and manage hypothyroidism or hyperthyroidism, they do not agree on how to interpret the TSH test results.

Until 2002, the official TSH "normal range" that laboratories and most doctors used throughout the U.S. was a range of 0.5 to 5.0.

On that range, a TSH under 0.5 (a low TSH) indicated hyperthyroidism (an overactive thyroid), and a TSH over 5.0 (a high TSH) indicated hypothyroidism (an underactive thyroid.)

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