TSH thyroid test results explained (Canada)

TSH is a hormone made by the pituitary gland in the brain. It tells the thyroid gland to make thyroid hormones. A TSH blood test is the usual first test of how the thyroid is working.

Also printed as: TSH, Thyroid test, Free T4.

What is on the report

Typical adult ranges. Each lab sets its own, so the range printed next to your result is the one that counts.

Test	What it is	Typical range
TSH	A brain hormone that tells the thyroid how hard to work.	0.3–4.2 mIU/L
Free T4	The active, unattached form of the thyroid's main hormone.	12–22 pmol/L
Free T3	The unattached form of T3, the most active thyroid hormone.	3.1–6.8 pmol/L

Good to know in Canada

TSH is usually reported in milliunits per litre (mU/L).
The normal range for TSH depends on the type of test the lab uses, so ranges vary a little between labs.
TSH rises when the thyroid is underactive, often before thyroid hormone levels fall. A TSH below the range can point to an overactive thyroid.
If TSH is high, free T4 may also be tested. The Thyroid Foundation of Canada notes that T3 and free T3 are not used to diagnose an underactive thyroid.

Call 911 in an emergency. For health advice that is not an emergency, call 811 in most provinces and territories. For questions about your results, contact your family doctor, nurse practitioner or the clinic that ordered the test.

Keep your reports in one place

Take a photo or screenshot of your lab report, or upload the PDF, and Vita explains each number in plain words, suggests what to ask your doctor, and keeps it with your past results. Vita does not connect to any Canadian health record system. Hospital connections are for US hospitals, not Canadian ones.

Vita Health Coach on the App Store

Ask it in ChatGPT

Vita Health Coach also answers in ChatGPT. One tap opens ChatGPT with this question ready to send:

“What should I ask the doctor about my Thyroid stimulating hormone (TSH) result?”

Ask in ChatGPT Add Vita Health Coach to ChatGPT

Questions

Why was free T4 added to my results?

When TSH is high, doctors often check free T4, the thyroid hormone that is free in the blood, to get a fuller picture of how the thyroid is working.

What if TSH is raised but free T4 is in range?

The Thyroid Foundation of Canada calls this pattern subclinical hypothyroidism. It notes that not every case needs treatment, and that your doctor decides based on your symptoms and overall health.

Can stress or anxiety change my TSH?

Anxiety, depression and stress can cause symptoms that feel like an underactive thyroid, but the Thyroid Foundation of Canada notes that they do not change TSH.

More for Canada

Sources

General information, not medical advice. VitaMedas is not connected with any government health service. Vita Health Coach explains; it never diagnoses. In an emergency, call 911. Read the medical disclaimer.