Thyroid blood tests are an important part of the process of diagnosing and managing thyroid conditions. Thyroid levels have implications for your treatment, and periodic testing is used to help guide changes to the dosage of your thyroid medications, including thyroid hormone replacement drugs used to treat hypothyroidism, and antithyroid drugs used to treat hyperthyroidism.
It is important to understand and track your thyroid test results so that you can be an active participant in your thyroid care, and knowledgeably advocate for changes you may need. To that end, here are a few important pointers.
The thyroid stimulating hormone (TSH) test is a key test used to evaluate thyroid function. You should always know the reference range — the range that represents a “normal” result — for this test at the lab that performs it for you. A typical range runs from, for example, .50 to 4.5. Levels below the cutoff represent hyperthyroidism and levels above the cutoff represent hypothyroidism.
The free thyroxine or free T4 test measures the amount of the storage hormone thyroxine available in your bloodstream. Different labs use different reference ranges, but generally, levels above the cutoff represent hyperthyroidism, and levels below the cutoff represent hypothyroidism.
The free triiodothyronine or free T3 test measures the amount of the active hormone available in your bloodstream. Different labs use different reference ranges, but generally, levels above the cutoff represent hyperthyroidism, and levels below the cutoff represent hypothyroidism.
Reverse T3, also known as RT3, measures an inactive form of the T3 hormone. The more elevated your RT3, the more of this inactive, blocking hormone is present in your bloodstream. Reverse T3 can interfere with your cells’ ability to take on actual T3, leaving you more hypothyroid at the cellular level.
Thyroid antibody tests such as thyroid peroxidase antibodies (TPO), thyroid receptor antibodies (TRAb), and thyroid stimulating immunoglobulins (TSI) measure the level of antibodies in your system, a marker for autoimmune activity. A reference range will be given, and a level within that range is considered "normal" or "no evidence of the autoimmune disease." A level that is on the borderline may be suspect for autoimmune disease. Levels above the reference range are evidence of autoimmune disease. There is also a correlation between the amount of elevation and the extent of autoimmune activity. A TPO level of 370, for example, is evidence of more inflammation and autoimmune attack on your gland, compared to a TPO level of 50.
Some other useful thyroid tests your physician may order include:
- Thyroglobulin (Tg)
- Anti-thyroglobulin Antibodies (TgAb)
If you are struggling with related symptoms such as weight gain, fatigue, or hair loss, your doctor may also regularly run tests including:
- Fasting glucose
- Hemoglobin A1C
- Vitamin D
Tracking your thyroid blood test results
One of the simplest ways to track your thyroid blood test results is in paper form. Make sure you get copies of all of your blood test results. (Double check that the reference range is included, and don’t accept simplified checklists, yes/no blood test results, or results postcards.) File them chronologically so that you can find results easily.
For electronic tracking, many people like to use a spreadsheet program such as Microsoft Excel, or Google Sheets. You can enter tests by date, and create separate columns for the low- and high-end reference range cutoffs, as well as a column for the result. This also allows you to sort and graph your test results.
There are also apps specifically designed for you to track your blood test results.
Blood Test Grapher, for example, lets your track and graph blood test results using your IOS tablet, or smartphone.
The Thyroid Tracker lets you track thyroid-specific blood test results using your desktop, IOS tablet, or smartphone.
MyMedLab is a company that allows patients to order their own blood tests without a doctor visit. The MyMedLab Thyroid App helps you assess your risks and symptoms of thyroid disease, and order your own laboratory tests from a tablet or smartphone. You can get more information on the MyMedLab Thyroid app in this Google Hangout. The Thyroid App is available free for IOS at the Apple store and in other formats at Google Play.
MyMedLab is one of several direct-to-consumer labs — including HealthLabs, HealthCheckUSA, and Any Lab Test Now — with an online platform that allows you to order your bloodwork online from a smartphone or desktop computer. Results are securely delivered to your private portal, where you can download PDF printings of your test results and see graphs of test results over time.
The goal of tracking thyroid blood test results
Remember that the goal is to use your thyroid test results to work with your healthcare provider to ensure that you are getting optimal treatment. For example:
- If your TSH is too high, and free T4 and free T3 are too low, you may need an increased dosage of thyroid hormone replacement medication to treat your hypothyroidism.
- If your TSH is within the reference range, but your free T4 and free T3 are too low, you may have subclinical hypothyroidism and warrant an increased dosage of medication.
- If you have low or low-normal free T3 levels and/or elevated reverse T3, you may need the addition of T3 — Cytomel, liothyronine, or a natural desiccated thyroid drug like Nature-throid or Armour — to your thyroid hormone replacement regimen.
- If you have a TSH, free T4, and free T3 within the reference range but you have elevated TPO antibodies, you may have Hashimoto’s thyroiditis that warrants treatment.
- If your TSH is within the reference range, but your free T4 and free T3 are too high, you may have subclinical hyperthyroidism and warrant an increased dosage of antithyroid medication.
- If your TSH is too low, and your free T4 and free T3 are too high, you may need an increased dosage of antithyroid medication.
- If you have a TSH, free T4, and free T3 within the reference range but you have elevated TSI or TRAb, you may have Graves’ disease that warrants treatment.
You can also keep track of the test levels associated with different dosages of medication, as well as symptoms. Tracking these factors allows you and your practitioner to finetune your treatment for the best possible results.