Is my TSH (Thyroid Stimulating Hormone) normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal TSH level?
TSH controls thyroid hormone production. High TSH means your thyroid is underactive (hypothyroidism) — causing fatigue, weight gain, and cold sensitivity. Low TSH means overactive (hyperthyroidism) — causing anxiety, weight loss, and rapid heart rate. The "normal" range of 0.5-4.5 mIU/L is debated; many functional medicine doctors prefer 0.5-2.5 mIU/L.
| Range | Values |
|---|---|
| Standard Reference | 0.5–4.5 mIU/L |
| Optimal | 0.5–2.5 mIU/L |
| Longevity Optimal | 0.5-2.5 mIU/L |
| High Risk | > 10 mIU/L |
| Low Risk | < 0.3 mIU/L |
What causes abnormal TSH levels?
High TSH (hypothyroidism) is caused by Hashimoto's thyroiditis (autoimmune), iodine deficiency, thyroid surgery or radiation, certain medications (lithium, amiodarone), and pituitary disorders. Low TSH (hyperthyroidism) can be caused by Graves' disease, thyroid nodules, excess iodine, or thyroiditis. Stress and poor sleep can also affect TSH levels.
When should you see a doctor?
See your doctor if TSH is above 4.5 mIU/L or below 0.5 mIU/L, if you have symptoms of hypothyroidism (fatigue, weight gain, cold intolerance, dry skin) or hyperthyroidism (anxiety, weight loss, heat intolerance, rapid heartbeat). Request Free T3 and Free T4 testing for a complete picture.
Where to get a TSH test
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Related biomarkers
These biomarkers are often tested alongside TSH for a more complete picture.
Frequently asked questions
What is a normal TSH level?
What does high TSH mean?
Should I also test Free T3 and Free T4?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.