Thyroid Level (TSH) Assessment
Interpret your TSH thyroid test result.
Understand if your level is normal, high (hypothyroid), or low (hyperthyroid) with context by age group.
TSH stands for Thyroid-Stimulating Hormone. It is produced by the pituitary gland in the brain and controls the thyroid gland’s production of T3 (triiodothyronine) and T4 (thyroxine) — the hormones that regulate metabolism, energy, body temperature, heart rate, and many other functions.
TSH works in an inverse feedback loop. When the thyroid is underactive and T3/T4 levels are low, the pituitary releases more TSH to stimulate the thyroid to produce more. When the thyroid is overactive and T3/T4 levels are too high, the pituitary reduces TSH output.
This means:
- High TSH = thyroid is underactive (hypothyroidism)
- Low TSH = thyroid is overactive (hyperthyroidism)
Standard reference ranges (mIU/L) for most labs:
- Normal adult: 0.4 – 4.0 mIU/L
- Optimal (many integrative practitioners): 1.0 – 2.5 mIU/L
- Pregnancy (first trimester): 0.1 – 2.5 mIU/L
- Seniors (65+): slightly higher range, up to 6.0 mIU/L can be acceptable
- Children: ranges vary by age — often 0.7 – 5.7 mIU/L in school-age children
Symptoms of high TSH (hypothyroidism) include fatigue, weight gain, cold intolerance, brain fog, constipation, dry skin, and depression.
Symptoms of low TSH (hyperthyroidism) include weight loss, rapid heartbeat, anxiety, sweating, heat intolerance, tremors, and insomnia.
A single TSH test is a starting point, not a complete diagnosis. Full thyroid panels also include Free T4, Free T3, Reverse T3, and thyroid antibodies (TPO and TgAb). Always discuss your results with a licensed healthcare provider — they will consider your symptoms, history, and full test panel before making any diagnosis or treatment recommendation.
Many factors temporarily affect TSH levels: stress, sleep deprivation, illness, biotin supplements, and the time of day the blood is drawn.