TPO Test (Thyroid Peroxidase Antibody)
This page explains the tpo test (thyroid peroxidase antibody), what it measures, and how to arrange it. The TPO test measures thyroid peroxidase antibodies, which are proteins your immune system makes that can attack the thyroid gland. It is ordered to help evaluate autoimmune thyroid conditions such as Hashimoto's thyroiditis or Graves' disease, especially when other thyroid tests are abnormal.
- Sample type
- blood
- Category
- Thyroid
- Turnaround
- 1-3 business days
- Price
- $158
- Referral
- Not required
The TPO test measures thyroid peroxidase antibodies, which are proteins your immune system makes that can attack the thyroid gland. It is ordered to help evaluate autoimmune thyroid conditions such as Hashimoto's thyroiditis or Graves' disease, especially when other thyroid tests are abnormal.
What it measures
- Thyroid peroxidase antibody (TPO Ab) — The main antibody measured; high levels suggest an autoimmune response against the thyroid.
- Thyroid-stimulating hormone (TSH) — Often checked alongside TPO to see how the thyroid is working.
- Free thyroxine (Free T4) — A thyroid hormone level that helps show if the gland is over- or underactive.
- Free triiodothyronine (Free T3) — Another thyroid hormone, sometimes included for a fuller picture.
Who it is for
A healthcare clinician typically orders this test when you have symptoms of a thyroid problem, an abnormal TSH level, or a known autoimmune condition.
Preparation
No fasting or special preparation is usually required for a TPO test. You can eat and drink normally unless your clinician gives other instructions.
Results and what they mean
Results are reported as a number, often with a reference range; a positive result means TPO antibodies were detected. Your clinician interprets the result along with your symptoms and other thyroid tests. This is general information, not medical advice; only a qualified professional can diagnose or treat a thyroid condition.
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 tpo test (thyroid peroxidase antibody) 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
Do I need to fast for a TPO test?
No, fasting is not typically needed. You can eat and drink as usual before the blood draw.
What does a positive TPO result mean?
It means antibodies against thyroid peroxidase were found. This can happen in autoimmune thyroid conditions, but it does not by itself confirm a diagnosis.
Can TPO antibodies go away?
Levels can change over time, but the presence of antibodies often persists. Your clinician will track trends with other tests.
Is this test painful?
It uses a standard blood draw from a vein, which feels like a quick pinch. Serious problems are rare.