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What Is Considered a Low TSH Level?

TSH, or thyroid stimulating hormone, is secreted by the pituitary gland and in turn stimulates the thyroid gland to secrete T3 and T4. When the thyroid produces too much T3 and T4 it can result in lower than normal TSH in the blood.

  1. The TSH Test

    • The laboratory test to measure TSH is also called TSH and requires a blood draw for testing. TSH is considered a routine lab test and results are generally obtained in just a few days.

    The Normal Range

    • TSH levels are considered normal for people who are not being treated for thyroid disease when they are between 0.4 and 4.0 mIU/L. For those who are already being treated for a thyroid condition, TSH between 0.5 and 3.0 mIU/L is considered within the normal range.

    Low TSH Levels

    • When TSH levels fall below the normal range, the resulting condition is called hyperthyroidism. If levels are below 0.5, it is important to discuss your symptoms with a doctor for a possible diagnosis.

    Causes of Low TSH

    • Low TSH is caused by a hyperactive thyroid, which may be caused by a tumor, abnormal grown, inflammation or infection of the thyroid.

    Symptoms of Hyperthyroidism

    • The most common symptoms of hyperthyroidism are fatigue, abnormal weight loss, an increased heart rate, anxiousness, shakiness and reduced tolerance to heat.

    Treatment of Hyperthyroidism

    • The most common treatment of hyperthyroidism is through anti-thyroid medication that must be taken daily. If the condition is caused by a tumor or abnormal growth of the thyroid, it may require partial or even total removal of the gland.

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