picardo.

TPO antibodies The main sign of Hashimoto’s

Also called Thyroid peroxidase antibodies, Anti-TPO, TPOAb and Antimicrosomal antibodies Not on a standard checkup No fasting needed

The short answer

TPO antibodies show whether your immune system is targeting your thyroid, the cause of Hashimoto’s. A positive result raises your chance of an underactive thyroid later, but on its own it doesn’t need treatment.4,7 Labcorp’s range for adults is 0 to 34 IU/mL.1

A good result
Under 35 IU/mL at Labcorp, which means no sign of thyroid autoimmunity.1
If yours is high
You’re not alone. In a large US survey, about 1 in 9 people had TPO antibodies.2 With a normal TSH, you need no treatment. Your TSH is the number to follow.4
Should you test?
It’s worth doing once if your TSH is high, or if you’ve had recurrent miscarriages or trouble getting pregnant. Repeating it rarely helps.3,4

Check your result

Type the number from your report. It stays on this page.

Which fits you best?

Use your TSH from the same blood draw, or a recent one. If you’re pregnant or trying to get pregnant, pick that option whatever your TSH.

35
  • Negative Under 35
  • Positive 35 or more

Enter your result to see what it means and what to do next.

Got a result from another lab? Ask Picardo about it. The app explains your results, and a physician can follow up.

The cutoff is Labcorp’s range for adults.1 The bar isn’t to scale.

What is a normal TPO antibodies level?

Labcorp’s range for adults is 0 to 34 IU/mL, so 35 or more is flagged as high.1 A higher level goes with a somewhat higher risk, but it doesn’t change what to do.4,7 What matters is whether you have antibodies, and what your TSH shows:3,4

Negative Under 35 IU/mL

No sign of thyroid autoimmunity

Your immune system isn’t targeting your thyroid, at least not with the antibody most closely tied to Hashimoto’s.2

How worried to be

Nothing to worry about.

What to do next
  1. 1 You don’t need to repeat this test.3
  2. 2 If you were tested after the first trimester of pregnancy, a negative result is less certain, because antibody levels fall as pregnancy goes on.4
  3. 3 If you’re pregnant and your result is close to 35, ask whether extra TSH checks make sense.4
Positive 35 IU/mL or higher, with a TSH in range

Positive, with a normal TSH: a risk, not a disease

Your immune system is making antibodies against your thyroid, but your thyroid is still working normally. The 2026 ATA guideline calls this a risk factor for thyroid disease, not a disease in itself.4 Some people go on to develop an underactive thyroid. In a 20-year UK study using older antibody tests, about 2% of women with antibodies alone did so each year.7

How worried to be

Not a worry now, but worth knowing for the future.

What to do next
  1. 1 You don’t need treatment, and you don’t need to repeat this test.3,4
  2. 2 Your TSH is the number to follow. No guideline sets a schedule when it’s normal, so ask your clinician how often to check it, and check it if symptoms appear.
  3. 3 If you’re planning a pregnancy, check TSH and free T4 every 3 to 6 months.4
Positive, TSH high 35 IU/mL or higher, with a high TSH

Positive, with a high TSH: likely Hashimoto’s

Together, a high TSH and TPO antibodies point to Hashimoto’s as the cause.2 In the 20-year UK study, women with both went on to an overt underactive thyroid at about 4% a year, against 3% with a high TSH alone.7 That’s why US guidelines count positive antibodies in favor of treatment when TSH is above the lab’s range but under 10.2

How worried to be

It depends on your TSH. If it’s 10 or more, or your free T4 is low, see a clinician within a few weeks. Otherwise it isn’t urgent.

What to do next
  1. 1 If this is your first high TSH, repeat TSH and free T4 in about 3 months before deciding.3
  2. 2 Ask whether levothyroxine makes sense for you, especially if you have symptoms.2
  3. 3 If you don’t start treatment, recheck TSH and free T4 about once a year.3
Positive, pregnancy 35 IU/mL or higher, if you’re pregnant or trying to get pregnant

Positive, and pregnant or trying: check TSH more often

TPO antibodies go with a higher chance of your thyroid becoming underactive before or during pregnancy, and slightly higher rates of miscarriage and early birth.4 Levothyroxine doesn’t improve those outcomes when your TSH is normal, so the 2026 ATA guideline now advises against it.4,5,6 Regular TSH checks catch the cases that do need treatment.4

How worried to be

Not a worry in itself, but stick to the testing plan.

What to do next
  1. 1 Before pregnancy, check TSH and free T4 every 3 to 6 months.4
  2. 2 Once pregnant, check TSH when it’s confirmed, then every 4 to 6 weeks until mid-pregnancy.4
  3. 3 If your TSH is over 4.0 in the first half of pregnancy, contact your obstetric clinician.4
  4. 4 After the birth, watch for postpartum thyroiditis. With TPO antibodies, the risk is 33% to 50%.4
TPO antibodies test, $6.25
Results in 2 to 3 days, explained in the app
Order

What are TPO antibodies?

TPO, short for thyroid peroxidase, is an enzyme your thyroid uses to make hormone. TPO antibodies are tags your immune system has put on it by mistake. Finding them tells you the thyroid is a target. Your TSH tells you whether it’s been damaged yet.

They’re found in most people with Hashimoto’s, which is the most common cause of an underactive thyroid in the US.2 They also turn up in many people whose thyroid works normally. In a large US survey using a sensitive test, about 1 in 9 people had them, more often women and older people.2,7

What does a positive result mean for your thyroid?

It raises your chance of an underactive thyroid over the years, especially if your TSH is already high.2,7

At the start Became underactive each year
Thyroid antibodies, normal TSHAbout 2%
High TSH, no antibodiesAbout 3%
High TSH and antibodiesAbout 4%

Women in the Whickham study in northern England, followed for 20 years and tested with older antibody tests. The rates are for an overt underactive thyroid, and were lower in men.2,7

Your TSH is the number to watch. Antibodies tend to stay once they appear, and their level doesn’t guide treatment.2,3

TPO antibodies and pregnancy

TPO antibodies matter most if you’re planning a pregnancy. In trials of women with TPO antibodies and a normal TSH who were trying to conceive, 7% to 9% developed an underactive thyroid, mostly mild, over about a year.4 Antibodies also go with slightly higher rates of miscarriage and early birth: 2 to 8 percentage points more for miscarriage, and 2 to 3 for early birth.4

For years, some clinicians gave levothyroxine to women with antibodies and a normal TSH, hoping to prevent miscarriage. Placebo-controlled trials have now tested it. In TABLET, 952 women with TPO antibodies and a history of miscarriage or infertility had the same live birth rate on levothyroxine as on a placebo: 37.4% against 37.9%.5 T4LIFE, which stopped early with 187 women with recurrent miscarriage, found no difference either.6

The 2026 ATA guideline, which replaced its 2017 version, now advises against levothyroxine for these women, and against selenium in pregnancy. It recommends regular TSH checks instead.4

Can you lower TPO antibodies?

Selenium is the most studied option. In a 2024 analysis of 35 trials, it lowered TPO antibody levels, but the trials didn’t follow people long enough to show whether it prevents an underactive thyroid.8 In CATALYST, a Danish trial, 412 people with Hashimoto’s on levothyroxine took selenium or a placebo for a year. Antibodies fell a little more with selenium, but quality of life improved the same in both groups.9 US guidelines advise against selenium for preventing or treating an underactive thyroid.2

Lowering the number isn’t the goal. What matters is how well your thyroid works, which TSH shows.

Who should get a TPO antibody test?

It’s worth checking once if any of these apply to you:

  • Your TSH is high.2,3
  • You’ve had recurrent miscarriages or trouble getting pregnant.4
  • You have type 1 diabetes or another autoimmune condition, or take lithium or amiodarone, where antibodies can show your risk.2

Once is enough for most people. UK guidelines advise against repeating the test.3

How to get a TPO antibodies test, and what it costs

A TPO antibodies test costs $6.25 through Picardo.

Order the test

TPO antibodies test

$6.25
Labcorp 006676 · no fasting needed
Order TPO antibodies
  • Results in 2 to 3 days, in the app
  • Physician follow-up if you want one
  • Free Labcorp draw, or $75 at home
  • No other fees. HSA and FSA eligible.
Already have a result? Ask Picardo about it

Questions people ask

Do TPO antibodies mean I have Hashimoto’s?

They’re its main sign, found in most people with it.2 But many people with TPO antibodies keep normal thyroid function. In the 20-year UK study, about a quarter of women with thyroid antibodies alone had developed an underactive thyroid by the end.7

Should I recheck my TPO antibodies?

Usually not. Once present they tend to stay, and the level doesn’t guide treatment, so UK guidelines advise testing once.2,3 Your TSH is the number to follow.

Are TPO antibodies linked to other autoimmune conditions?

Yes. Autoimmune thyroid disease is more common with type 1 diabetes, pernicious anemia, celiac disease, rheumatoid arthritis and lupus.2 About 10% of people with type 1 diabetes develop chronic thyroiditis.2

What’s the difference between TPO and thyroglobulin antibodies?

Both target the thyroid, but TPO antibodies are more closely tied to an underactive thyroid, so guidelines use them first.2,4

Does biotin affect the test?

It can. High-dose biotin, common in hair, skin and nail supplements, interferes with many thyroid tests. Labcorp asks you to stop it at least 72 hours before the draw.1

Often checked alongside

TSH
The first test for thyroid function
Thyroglobulin antibodies
A second autoimmune thyroid marker
Free T4
Main thyroid hormone, converted into the more active T3
Free T3
Active thyroid hormone that regulates metabolism and energy use

Test details

Labcorp test
Thyroid Peroxidase (TPO) Antibodies, 006676
LOINC
8099-4
Sample
Blood
Fasting
Not needed
Typical lab range
0 to 34 IU/mL for adults over 19, with lower limits for children1
Units
IU/mL

Sources

  1. 1 Labcorp. Thyroid peroxidase (TPO) antibodies, test 006676. Labcorp test menu. Accessed October 28, 2026. www.labcorp.com/tests/006676/thyroid-peroxidase-tpo-antibodies
  2. 2 Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid. 2012;22(12):1200–1235. doi.org/10.1089/thy.2012.0205
  3. 3 National Institute for Health and Care Excellence. Thyroid disease: assessment and management. NICE guideline NG145. London: NICE; 2019. Updated October 12, 2023. www.nice.org.uk/guidance/ng145
  4. 4 Korevaar TIM, Leung AM, Alexander EK, et al. American Thyroid Association 2026 guidelines for thyroid disease in preconception, pregnancy, and postpartum. Thyroid. 2026;36(5):481–544. doi.org/10.1177/10507256261445624
  5. 5 Dhillon-Smith RK, Middleton LJ, Sunner KK, et al. Levothyroxine in women with thyroid peroxidase antibodies before conception. N Engl J Med. 2019;380(14):1316–1325. doi.org/10.1056/NEJMoa1812537
  6. 6 van Dijk MM, Vissenberg R, Fliers E, et al. Levothyroxine in euthyroid thyroid peroxidase antibody positive women with recurrent pregnancy loss (T4LIFE trial): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Diabetes Endocrinol. 2022;10(5):322–329. doi.org/10.1016/S2213-8587(22)00045-6
  7. 7 Vanderpump MPJ. The epidemiology of thyroid disease. Br Med Bull. 2011;99:39–51. doi.org/10.1093/bmb/ldr030
  8. 8 Huwiler VV, Maissen-Abgottspon S, Stanga Z, et al. Selenium supplementation in patients with Hashimoto thyroiditis: a systematic review and meta-analysis of randomized clinical trials. Thyroid. 2024;34(3):295–313. doi.org/10.1089/thy.2023.0556
  9. 9 Larsen C, Winther KH, Cramon PK, et al. Selenium supplementation and placebo are equally effective in improving quality of life in patients with hypothyroidism. Eur Thyroid J. 2024;13(1):e230175. doi.org/10.1530/ETJ-23-0175

Updated 28 Oct 2026.

This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.