What it measures
- Thyroid peroxidase (TPO) antibodies
What are TPO antibodies?
Thyroid peroxidase is an enzyme the thyroid uses to make hormones. In autoimmune thyroid disease, the immune system makes antibodies against it. High TPO antibodies are found in most people with Hashimoto’s thyroiditis, the most common cause of an underactive thyroid in the UK, and in many people with Graves’ disease.
Raised antibodies with normal thyroid hormones mean you have a higher chance of developing an underactive thyroid in future, so your GP may suggest checking your thyroid function regularly.
For the full picture, pair this test with our Thyroid Function Blood Test.
Who it’s for
- Borderline or abnormal thyroid function results
- A family history of thyroid disease
- Other autoimmune conditions, such as type 1 diabetes or coeliac disease
- Planning a pregnancy with a history of thyroid problems
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
- Stop biotin (vitamin B7) supplements 48 hours before, as biotin can affect hormone and thyroid results.
Thyroid (Peroxidase Antibodies) Blood Test: your questions
Can I have thyroid antibodies with normal thyroid levels?
Yes. Many people have raised TPO antibodies with normal thyroid function. It means a higher chance of thyroid problems later, so regular checks are sensible.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.