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Recommended TSH Levels

Thyroid-stimulating hormone, or TSH, levels help diagnose thyroid disorders. Your doctor may order this blood test if you complain of symptoms such as fatigue, constipation, dry skin, weight gain or hair loss. TSH blood levels are routinely measured on newborns as a normal screening process. If you take medication to improve the function of your thyroid, TSH levels will tell your doctor if the medication is working.

  1. TSH Explained

    • When blood levels of thyroid hormone are low, your pituitary gland releases TSH. TSH stimulates the production of the thyroid hormones triiodothyronine and thyroxine. Once these hormones have reached the proper level in your blood, TSH production stops. If your thyroid is producing low levels of thyroid hormones, your TSH level will increase. TSH is continually stimulating the production of hormones but these hormones are not being produced, so the TSH level stays high. If your thyroid is constantly producing hormones, levels of TSH are low because it is not needed.

    Recommended Reference Levels

    • To determine reference levels for blood tests, many healthy adults are tested. The results are then tabulated, and a normal range is established. This is what doctors use to decide if your results are within normal. Your doctor considers health history, results from other lab work and his personal knowledge of your lifestyle when interpreting results. In November 2002, the American Association of Clinical Endocrinologists recommended physicians use a narrow range of 0.3 to 3.0 mlU/L as a reference range for TSH levels. Not all labs and physicians have adopted these tighter guidelines and continue to use 0.4 to 4.0 mlU/ml as a reference range.

    Variation in TSH Levels

    • TSH levels are higher in the morning. The hormone is released while you sleep and used while you are awake. Lab tests done early in the morning can show higher levels. As people get older, TSH levels decrease. They also can decrease after consumption of high-glucose food and then increase slightly a few hours later. TSH levels are higher in obese people and can decrease after weight loss.

    Medications That Affect TSH Levels

    • Some medications can alter the results of your TSH test and should not be taken before the test. These are amiodarone, lithium, prednisone, potassium iodide and anti-thyroid medications. Check with your health care provider to make sure it is safe for you to miss a dose of medication before you take the test.

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