--- title: TSI (Thyroid-Stimulating Immunoglobulin) Test type: test id: tsi url: "https://www.test-well.com/tests/thyroid-stimulating-immunoglobulin-tsi" price_usd: 114.99 lab_fee_usd: 6 all_in_usd: 120.99 category: Thyroid sample: Blood draw fasting_required: false results_in: "3–5 business days" labs: - Quest orderable: true order_url: "https://www.test-well.com/cart?add=thyroid-stimulating-immunoglobulin-tsi&utm_source=ai_agent&utm_medium=markdown" --- # TSI (Thyroid-Stimulating Immunoglobulin) Test > Detects the antibodies that switch the thyroid on in Graves' disease — the most specific blood test for Graves' hyperthyroidism, measured from a standard blood draw. At TestWell it costs $114.99 plus a $6 lab fee, needs no fasting, and results post in 3–5 business days. Physician-authorized with no doctor's visit or insurance needed; draw at Quest. ## Key facts | Fact | Value | | --- | --- | | Price | $114.99 + $6 lab processing fee per order ($120.99 all-in for this test alone) | | Sample | Blood draw | | Fasting | Not required | | Results | 3–5 business days | | Labs | Quest Diagnostics | | Biomarkers measured | 1 | | Physician authorization | Included — no doctor's visit, referral or insurance needed | | Payment | Card, HSA or FSA; cash-pay only (no insurance billing) | ## What does the TSI (Thyroid-Stimulating Immunoglobulin) test tell you? Detects the antibodies that switch the thyroid on in Graves' disease — the most specific blood test for Graves' hyperthyroidism. Thyroid-stimulating immunoglobulins are antibodies that bind the TSH receptor and drive the thyroid to overproduce hormone. They are the cause of Graves' disease, and this assay measures their stimulating activity directly, which is why a positive TSI in someone with a low TSH and high thyroid hormones confirms Graves' as the cause rather than a toxic nodule or thyroiditis. Endocrinologists also use TSI to follow Graves' disease over time, to judge the likelihood of remission before stopping antithyroid medication, and during pregnancy in women with current or past Graves' disease, because high levels in the third trimester predict thyroid problems in the newborn. TSI is often ordered together with the TSH receptor antibody (TRAb) test: TRAb detects any antibody that binds the receptor, TSI specifically the ones that stimulate it. Not available through BioReference, so it cannot be collected in New York or New Jersey. ## Biomarkers measured - Thyroid-Stimulating Immunoglobulin (TSI) ## Price by lab | Lab | Test price | All-in (with $6 fee) | Notes | | --- | --- | --- | --- | | Quest Diagnostics | $114.99 | $120.99 | Choose at checkout; walk-in patient service centers nationwide (not NY/NJ) | Rhode Island is not served. Prices are identical online and in the lab; no draw fee or physician fee is added. ## How much does a TSI (Thyroid-Stimulating Immunoglobulin) test cost? A TSI (Thyroid-Stimulating Immunoglobulin) test costs $114.99 at TestWell — $120.99 all-in when ordered alone, because the $6 lab processing fee is charged once per order, with no draw fee or physician fee added. Hospital outpatient labs typically bill around $350.00 self-pay for the same test, and often more. With insurance, what you pay depends on your deductible and your plan's negotiated rate; TestWell's price is fixed before the draw and is HSA/FSA-eligible. | Where you order | Price | One test, all-in | Notes | | --- | --- | --- | --- | | TestWell (drawn at Quest or Labcorp) | $114.99 | $120.99 | Includes the one $6 lab processing fee, charged once per order | | Hospital outpatient lab, self-pay (typical) | $350.00 | $350.00 | Reference figure; hospital charges vary widely by facility and are often higher | Lab test codes: Quest test code 30551. ## How do you prepare? No fasting required. Stop high-dose biotin supplements at least 2 days before the draw. ## How to order 1. Add to cart: https://www.test-well.com/cart?add=thyroid-stimulating-immunoglobulin-tsi&utm_source=ai_agent&utm_medium=markdown 2. Create an account or sign in, confirm your state and preferred lab, pay by card, HSA or FSA. 3. A licensed physician authorizes the order (usually within minutes); the requisition arrives by email. 4. Walk into any Quest Diagnostics patient service center — no appointment needed at most sites. 5. Results post to your TestWell portal in 3–5 business days with reference ranges and flags. ## Related - [Free T3 (Triiodothyronine)](https://www.test-well.com/tests/free-t3) — $30.99 - [Free T4 (Thyroxine)](https://www.test-well.com/tests/free-t4-test) — $23.99 - [Reverse T3](https://www.test-well.com/tests/reverse-t3) — $35.99 - [T3 Uptake](https://www.test-well.com/tests/t3-uptake-test) — $22.99 - [T3, Total (Triiodothyronine)](https://www.test-well.com/tests/total-t3-test) — $24.99 - [All Thyroid tests](https://www.test-well.com/tests/category/thyroid) - [Full test directory](https://www.test-well.com/tests/directory) --- Canonical page: https://www.test-well.com/tests/thyroid-stimulating-immunoglobulin-tsi Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.