Is my Anti-TPO (Thyroid Peroxidase Antibodies) normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Anti-TPO level?
Anti-TPO antibodies target thyroid peroxidase, the enzyme responsible for thyroid hormone synthesis. Standard labs consider < 35 IU/mL normal (allowing some antibodies), but functional medicine targets < 2 IU/mL — as close to zero as possible. Anti-TPO is positive in ~90% of Hashimoto's cases, flagging autoimmune thyroid destruction often years before TSH becomes abnormal. Levels above 100 IU/mL are strongly associated with progressive thyroid destruction. Testing antibodies even when TSH is normal catches early autoimmune thyroid disease that standard testing would miss. Approximately 10-12% of the general population has elevated anti-TPO.
| Range | Values |
|---|---|
| Standard Reference | 0–34 IU/mL |
| High Risk | > 100 IU/mL |
What causes abnormal Anti-TPO levels?
Elevated anti-TPO is caused by Hashimoto's thyroiditis (autoimmune thyroid destruction), Graves' disease (autoimmune hyperthyroidism), and other autoimmune conditions (type 1 diabetes, rheumatoid arthritis, lupus — autoimmune diseases often cluster). Risk factors include female sex (5-10x higher risk), family history, other autoimmune diseases, high iodine intake, and viral infections (Epstein-Barr virus has been implicated).
When should you see a doctor?
See your doctor if anti-TPO is above 34 IU/mL, especially if TSH is also trending upward or you have hypothyroid symptoms (fatigue, weight gain, cold intolerance, dry skin, hair loss). If anti-TPO is above 100 IU/mL, discuss proactive thyroid monitoring and potential early intervention. Women planning pregnancy should be especially vigilant — Hashimoto's increases miscarriage risk.
Anti-TPO and longevity
Hashimoto's thyroiditis is the most prevalent autoimmune disease worldwide, affecting up to 5% of the population. The autoimmune destruction of the thyroid gland is gradual — anti-TPO antibodies can be elevated for 5-15 years before TSH crosses the clinical threshold. This silent phase represents a window for early intervention. Selenium supplementation (200 µg/day as selenomethionine) has been shown in multiple randomized controlled trials to reduce anti-TPO levels by 20-40%, likely by supporting selenoprotein-dependent antioxidant defenses in thyroid tissue. The gut-thyroid axis is an emerging area of research — intestinal permeability and dysbiosis may drive molecular mimicry that initiates thyroid autoimmunity. Autoimmune conditions tend to cluster: having Hashimoto's increases risk for other autoimmune diseases, making it an important systemic warning signal.
Where to get a Anti-TPO test
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Related biomarkers
These biomarkers are often tested alongside Anti-TPO for a more complete picture.
Frequently asked questions
What is a normal anti-TPO level?
What is Hashimoto's thyroiditis?
Can anti-TPO be elevated with normal TSH?
Can you have Hashimoto's with normal TSH?
Can anti-TPO levels be lowered?
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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.