Quick Facts
- Sample: Blood draw (serum)
- Fasting: Not required
- Turn-around: 6-7 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Early Graves' disease detection - Identify autoimmune thyroid conditions before complications develop
- No doctor visit required - Order conveniently online with confidential results
- Pregnancy risk assessment - Screen for neonatal thyrotoxicosis risk in expecting mothers
- Fast, accurate results - High-precision bioassay testing with 6-7 day turnaround
- Comprehensive thyroid insights - Differentiate hyperthyroidism causes when symptoms are unclear
- Preventive health monitoring - Track autoimmune thyroid activity for proactive wellness management
Who Is This Test For?
- Individuals experiencing hyperthyroidism symptoms (weight loss, tremors, rapid heartbeat)
- People with family history of autoimmune thyroid disorders
- Pregnant women with previous thyroid disease needing fetal risk assessment
- Those requiring differential diagnosis between thyroid condition causes
- Individuals monitoring Graves' disease treatment progress or potential relapse
- Health-conscious consumers seeking proactive thyroid autoimmune screening
How It Works – Just 3 Steps
- Order online - Select your test and schedule appointment at nearby lab location
- Visit lab - Quick blood draw with no fasting or special preparation required
- Get results - Receive confidential results within 6-7 days
FAQ
What does the TSI test measure? It measures thyroid-stimulating immunoglobulin antibodies that mimic TSH and overstimulate thyroid hormone production.
How accurate is this test for Graves' disease? The TSI test has high sensitivity and specificity for diagnosing Graves' disease, the most common hyperthyroidism cause.
Can I take this test while pregnant? Yes, it's especially important during pregnancy to assess neonatal thyrotoxicosis risk if you have thyroid history.
Do I need to stop medications before testing? No medication adjustments are typically required unless specifically instructed by your healthcare provider.
What if my results are abnormal? Elevated TSI levels suggest autoimmune thyroid activity and warrant consultation with an endocrinologist or primary care physician.
How long do results take? Most results are available within 6-7 business days
More Details
What is the purpose of this test?
The TSI blood test measures thyroid-stimulating immunoglobulin antibodies that mimic thyroid-stimulating hormone (TSH), causing excessive thyroid hormone production and hyperthyroidism. It primarily diagnoses Graves' disease, an autoimmune condition affecting approximately 0.5% of the U.S. population, with women being 7-8 times more likely to develop it than men (Healthline 2019). The test also helps assess pregnancy-related thyroid risks and differentiate various causes of thyroid dysfunction using highly accurate bioassay or immunoassay methods.
Who would benefit from this test?
This test benefits individuals experiencing hyperthyroidism symptoms like unexplained weight loss, heart palpitations, tremors, or fatigue. Pregnant women with thyroid disease history should consider testing to evaluate neonatal thyrotoxicosis risk. Healthcare providers use it for differential diagnosis when thyroid dysfunction causes are unclear, and patients monitoring Graves' disease treatment or potential relapse find it valuable (Mayo Clinic Labs 2025). Those with family history of autoimmune thyroid conditions can use it for preventive screening.
When should I order the TSI test?
Order this test when experiencing hyperthyroidism symptoms including rapid weight loss, increased heart rate, tremors, muscle weakness, or restlessness. Pregnant women with previous thyroid disorders should test to assess fetal risk. Healthcare providers may recommend it when clinical signs suggest Graves' disease but require confirmation, or when monitoring autoimmune thyroid disease progression (Cleveland Clinic Labs 2025). Consider testing if you have family history of autoimmune thyroid conditions for early detection.
How do I interpret the results?
TSI Index: < 1.3 (130%)
- What it means: Normal range
- Typical action: No immediate action needed
TSI Index: ≥ 1.3 (130%)
- What it means: Elevated - suggests Graves' disease
- Typical action: Consult endocrinologist
TSI Index: Significantly elevated
- What it means: Strong indication of autoimmune hyperthyroidism
- Typical action: Immediate medical evaluation
Results should always be interpreted alongside clinical symptoms and other thyroid function tests by a qualified healthcare provider.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
No fasting or special dietary restrictions are required for the TSI test. You can take medications as prescribed unless your healthcare provider specifically instructs otherwise. The blood sample is collected through a simple venipuncture procedure, similar to routine blood draws. Maintain your normal activities and diet before testing. If you're pregnant or have existing thyroid conditions, inform the lab staff, though this won't affect the testing procedure (Mount Sinai 2024).
How often should I get tested?
- Initial screening with symptoms: Once, then as directed by physician
- Monitoring Graves' disease treatment: Every 3-6 months
- Pregnancy with thyroid history: Each trimester or as recommended
- Post-treatment surveillance: Every 6-12 months
- Family history screening: Every 2-3 years or with symptoms
Why early detection matters
Early TSI detection prevents serious complications including thyroid storm, a life-threatening condition requiring emergency treatment. Timely Graves' disease diagnosis enables prompt treatment, reducing risks of heart problems, bone loss, and eye complications (Frontiers in Endocrinology 2025). For pregnant women, early identification helps prevent neonatal thyrotoxicosis, improving outcomes for both mother and baby. Proactive monitoring allows for lifestyle modifications and treatment adjustments that maintain optimal thyroid function and prevent disease progression.
Related tests you may consider
Thyrotropin Receptor Antibody (TRAb) Test - Detects additional thyroid-stimulating or blocking antibodies for comprehensive autoimmune assessment.
Thyroid Peroxidase Antibodies (TPOAb) - Diagnoses Hashimoto's thyroiditis and other autoimmune hypothyroid conditions.
Thyroglobulin Antibodies - Additional autoimmune thyroid marker often ordered with TSI testing for complete autoimmune thyroid assessment.
