TSI Test
TSI Test can be requested without a referral, and this overview covers what to expect. The TSI (Thyroid-Stimulating Immunoglobulin) test is a blood test that measures antibodies that can overstimulate the thyroid gland. It is most often ordered to help diagnose Graves' disease, an autoimmune condition that causes hyperthyroidism, and to monitor treatment response.
- Sample type
- blood
- Category
- Thyroid
- Turnaround
- 1-3 business days
- Price
- $119
- Referral
- Not required
The TSI (Thyroid-Stimulating Immunoglobulin) test is a blood test that measures antibodies that can overstimulate the thyroid gland. It is most often ordered to help diagnose Graves' disease, an autoimmune condition that causes hyperthyroidism, and to monitor treatment response.
What it measures
- TSI level — The amount of thyroid-stimulating immunoglobulin in the blood; higher levels suggest Graves' disease.
- TSI index — A calculated ratio that compares your TSI level to a reference standard, helping interpret results.
- TSI percentage — Sometimes reported as a percentage of a normal reference range, indicating relative antibody activity.
- Thyroid-stimulating antibody (TSAb) — A related antibody that may be measured alongside TSI to assess thyroid stimulation.
Who it is for
A doctor typically orders a TSI test when you have symptoms of hyperthyroidism, such as unexplained weight loss, rapid heartbeat, or tremors, or when other thyroid tests suggest Graves' disease.
Preparation
No fasting or special preparation is needed for a TSI test. You can eat and drink normally before your blood draw.
Results and what they mean
Results are usually reported as a number or percentage, with a reference range provided by the lab. Your clinician will interpret your TSI level along with your symptoms and other thyroid tests. This information is general and not a substitute for medical advice.
How to order this test
- Choose the test and place a confidential order online.
- Select a certified collection site and pick a time that suits you.
- Have your specimen collected — most draws take only a few minutes.
- Review results in a secure portal, typically within 1–3 days.
Preparation, hours, and pricing vary by site; confirm details directly with the lab before your visit.
Availability by state
Direct-access online ordering for the tsi test is available in most states. It is currently unavailable in 6 states:
Everywhere else you can order confidentially and collect your sample at a certified site. Browse by state →
Frequently asked questions
What does a high TSI level mean?
A high TSI level often points to Graves' disease, but only your doctor can confirm a diagnosis after reviewing all your test results and symptoms.
Do I need to fast before a TSI test?
No, fasting is not required. You can eat and drink as usual before the blood draw.
How long does it take to get TSI test results?
Results are typically available within 1 to 3 business days, though this can vary by laboratory.
Can TSI levels change over time?
Yes, TSI levels can rise or fall with treatment or over the course of the condition. Your doctor may repeat the test to monitor changes.