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Thyroid-Stimulating Immunoglobulin, Serum — Substance Concentration

Published: August 9, 2026Updated: August 16, 2026

Measures thyroid-stimulating antibodies in blood to help evaluate autoimmune thyroid disease, especially Graves disease.

Quick summary

["A positive TSI test can support a diagnosis of Graves disease, but results must be interpreted with other thyroid tests."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
32214-9
Short code
TSI Ser-sCnc
Synonyms
TSI Ser-sCnc
Category
thyroid
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

The thyroid-stimulating immunoglobulin (TSI) test measures antibodies that can attach to receptors on thyroid cells and stimulate thyroid hormone production. It is performed on a blood sample.

Why might I need this test?

This test may be used when symptoms or other laboratory results suggest an overactive thyroid or Graves disease, an autoimmune condition that causes excess thyroid hormone. It may also be used to monitor certain thyroid conditions.

How is the test performed?

A healthcare professional draws blood from a vein, usually in an arm. The laboratory uses an immunoassay to measure thyroid-stimulating antibodies in the serum.

How do I prepare for the test?

Fasting is generally not required for this blood test. Tell your healthcare professional if you are pregnant, recently received thyroid treatment, or are taking medicines that may affect thyroid test results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TSI test

Frequently asked questions

Does a positive TSI result always mean Graves disease?
No. A positive result is strongly associated with Graves disease, but it must be interpreted with thyroid hormone tests, symptoms, and medical history.
Is the TSI test the same as a thyroid receptor antibody test?
They measure related thyroid-receptor antibodies, but the laboratory methods and reported values may differ. Your clinician will interpret the specific test ordered.
Do I need to fast before the TSI test?
Fasting is usually unnecessary unless your healthcare professional gives different instructions. Always follow the preparation directions provided for your appointment.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy