Anti-TPO (Thyroid Peroxidase) Antibody Test

The Anti-TPO (Thyroid Peroxidase) antibody test measures the level of antibodies in your blood that target thyroid peroxidase, an enzyme your thyroid gland needs to produce hormones. When your immune system mistakenly attacks this enzyme, it can disrupt normal thyroid function. Also known as TPOAb or Antithyroid Microsomal Antibody, this test is ordered to detect autoimmune causes of thyroid disease. A small sample of blood drawn from a vein in your arm is all that is needed.

A doctor may request this test for several reasons, from investigating unexplained symptoms to confirming a suspected diagnosis.

Common Symptoms That May Require This Test

• Persistent fatigue or low energy without a clear cause
• Unexplained weight gain or weight loss
• Unusual sensitivity to cold or heat
• Dry skin, brittle hair, or hair loss
• Constipation or changes in bowel habits
• Irregular menstrual periods in women
• Swelling at the front of the neck (goitre)

Conditions This Test Can Help Detect

The Anti-Thyroid Peroxidase test can help identify a range of conditions. These include:

• Hashimoto's thyroiditis, where TPO antibodies are present in roughly 90% of cases
• Graves' disease, with antibodies detected in 60% to 80% of patients
• Atrophic thyroiditis and primary myxoedema (severe underactive thyroid causing skin thickening)
• Postpartum thyroiditis, an autoimmune condition that can develop within a year of childbirth
• Non-thyroid autoimmune conditions such as pernicious anaemia, type 1 diabetes, and rheumatoid arthritis

No complex preparation is needed for this test, but a few simple steps will help ensure accurate results.

Do You Need to Fast?

No, fasting is not required for a standalone TPOAb test. If your doctor has ordered additional tests alongside this one, some of those may require fasting for 8 to 12 hours. Check with your doctor or the collection centre when booking.

Practical Tips Before Your Test

• Avoid biotin supplements (vitamin B7, including hair, skin, and nail supplements) for at least 72 hours before collection
• Inform your doctor or phlebotomist about all medications you are currently taking
• Stay well hydrated before your blood draw
• Wear a short-sleeved or loose-fitting top for easy access to your arm
• Antibody levels remain stable throughout the day, so there is no need to worry about the time of your appointment

Step-by-Step Procedure

1. A trained phlebotomist cleans a small area on your arm with an antiseptic wipe.
2. A soft elastic band is tied around your upper arm to make a vein easier to locate.
3. A small needle is gently inserted into the vein, and a small amount of blood is drawn into a collection tube.
4. The needle is removed, and a cotton ball or small bandage is placed over the site to stop any minor bleeding.
5. The entire blood draw typically takes only a few minutes and causes minimal discomfort.
6. Your sample is labelled and sent to the laboratory for analysis.

Factors That Can Affect Accuracy

• Biotin (vitamin B7) supplements taken within 72 hours of the test
• Medications such as interferons, lithium, or amiodarone
• Prior exposure to animal antigens, which can interfere with laboratory reagents
• Differences in testing methods between laboratories (reference ranges may vary)

While no lifestyle change replaces medical treatment, these general habits support overall thyroid and immune health:

• Eat a balanced diet that includes selenium-rich foods such as Brazil nuts and sunflower seeds, as selenium plays a role in thyroid function.
• Maintain adequate vitamin D levels; speak to your doctor if you suspect a deficiency.
• Manage stress through regular physical activity, adequate sleep, and relaxation practices, as chronic stress may contribute to autoimmune activity.