Thyroid blood test (full panel)
The great impersonator of women's health, checked properly. Not just TSH, but what your thyroid is actually producing and whether your immune system is involved.
The thyroid panel measures five markers: TSH, free T4, free T3 and two thyroid antibodies. It is $89, and a KnowLuna doctor can request it for you at no extra charge. Add a 20-minute video consult for +$59 if you want your results explained. Collect at an accredited Australian centre, or choose a home kit or a nurse visit at checkout (options below).
Thyroid conditions are far more common in women than men, and the symptoms are so ordinary that they get put down to work, age, motherhood or stress for years. That is why the thyroid is worth checking properly rather than in passing.
What it measures
- TSH (thyroid-stimulating hormone): not a thyroid hormone at all, but the pituitary's instruction to the thyroid. It rises when the thyroid is under-performing and falls when the thyroid is producing too much, which makes it the sensitive first-line marker.
- Free T4 (thyroxine): the main hormone the thyroid releases, measured as the unbound portion available to your tissues. It shows what the gland is actually producing rather than what it is being asked for.
- Free T3 (triiodothyronine): the more active hormone, mostly converted from T4 in the body. It adds detail, particularly where TSH and free T4 do not agree.
- Thyroid peroxidase antibodies (anti-TPO): the marker of autoimmune thyroid activity. Raised antibodies help explain why thyroid function is drifting and flag a higher chance of it changing over time.
- Thyroglobulin antibodies: a second autoimmune marker, read alongside anti-TPO for a fuller picture.
Who it's for
Anyone who is tired, foggy, flat, cold, losing hair, gaining or losing weight without explanation, or noticing that their heart races or their periods have changed. It is also worth doing before trying to conceive, in early pregnancy if your doctor advises, in the year after birth, and during perimenopause when the same symptoms have two possible explanations. It is for adults aged 18 and over. If a thyroid condition already runs in your family, a baseline is useful. If you are pregnant, tell us and your doctor, so the result is read against the trimester-specific ranges rather than the non-pregnant adult ranges shown below.
What you'll learn, and what you won't
You will learn whether your thyroid is under-active, over-active or working normally, whether that picture is mild or clear-cut, and whether an autoimmune process is behind it. Each marker is shown against your laboratory's range in plain English.
What a single panel will not do is settle it. A blood test is one input to a doctor's assessment, not a diagnosis on its own. Thyroid results shift with acute illness, pregnancy, some medicines and even the time of day, so borderline results are usually repeated a few weeks later before anyone draws conclusions.
TSH alone, or the full panel?
TSH on its own is a good screening test and is what most GPs order first. It is genuinely sensitive: if TSH is squarely normal, significant thyroid disease is unlikely. The reason this panel goes further is that TSH answers only one question.
- When TSH is abnormal, free T4 and free T3 tell you how far the gland has actually moved, which is the difference between a mild pattern that is watched and a clear one that is acted on.
- When TSH is borderline, antibodies show whether an autoimmune process is present and predict whether it is likely to drift further. They do not explain symptoms on their own.
- When you are planning pregnancy or newly postpartum, antibodies matter, because they raise the chance of thyroid changes in the year after birth.
- When results and symptoms disagree, having all five markers from one collection saves you a second trip to the collection centre.
The two patterns, in plain English
High TSH with a low free T4 means the pituitary is calling loudly and the thyroid is not keeping up: an under-active thyroid. Typical symptoms are tiredness, feeling cold, constipation, dry skin, hair thinning, low mood, heavier or more frequent periods, and weight that creeps up. If TSH is high but free T4 is still normal, that milder pattern is often monitored rather than acted on immediately.
Low TSH with a high free T4 or free T3 is the opposite: an over-active thyroid. Typical symptoms are a racing or irregular heartbeat, heat intolerance, sweating, anxiety, tremor, loose bowels, lighter or absent periods, and weight loss. Your doctor decides what follow-up or referral is appropriate.
Thyroid and women
Thyroid function touches most of women's health. It influences how regularly you ovulate and how heavy your periods are, so an unchecked thyroid is a common finding behind irregular cycles, which is why TSH sits in the fertility panel as standard. Untreated thyroid problems can also make conceiving harder and matter in pregnancy, so it is worth knowing your numbers beforehand.
After birth, thyroid function changes in a meaningful minority of women, sometimes swinging over-active before settling under-active, and it is easily mistaken for normal newborn exhaustion. It is part of the postpartum recovery panel for that reason. In perimenopause, the overlap is almost complete: fatigue, brain fog, poor sleep, palpitations and mood change belong to both stories, and only a blood test separates them.
Reference ranges and what they mean
| Marker | Typical adult range | What it usually means |
|---|---|---|
| TSH | About 0.4 to 4.0 mIU/L | Within range makes significant thyroid disease unlikely. Above it suggests an under-active gland, below it an over-active one. |
| Free T4 | Roughly 10 to 20 pmol/L in adults | Read with TSH. A low free T4 with a high TSH is the classic under-active pattern. |
| Free T3 | Roughly 3.5 to 6.5 pmol/L in adults | Adds detail, and is most useful when TSH is low or the picture is unclear. |
| Thyroid peroxidase antibodies | Reported as negative or positive against the laboratory's cut-off | A positive result points to autoimmune thyroid activity. Some people carry antibodies with normal function. |
| Thyroglobulin antibodies | Reported as negative or positive against the laboratory's cut-off | Read alongside anti-TPO. On its own it is less informative. |
Ranges vary by laboratory; your report shows the range your lab uses. Pregnancy has its own trimester-specific ranges.
When to do this test
No fasting is needed. A morning collection is preferred, because TSH is naturally higher overnight and early in the morning and drifts down through the day; testing at a consistent time makes repeat results easier to compare.
Two practical points. If you take high-dose biotin (it is common in hair, skin and nail formulations), pause it for about 72 hours before collection, because it can interfere with the assay and produce misleading thyroid results. And avoid testing during or straight after a significant illness, when thyroid results are often temporarily abnormal. If your doctor has already prescribed thyroid medication, keep taking it as directed and tell us, since timing relative to your dose affects the reading.
How it works
- Order online. Either upload the request your own doctor has signed, or a KnowLuna doctor requests the panel for you at no extra charge.
- Collect at an accredited centre near you, or choose a home kit or a nurse visit (options below). Morning is ideal, no fasting, and pause high-dose biotin for 72 hours.
- Results are usually ready within a few business days, explained in your account, with an optional consult to talk them through.
Choose how you collect
Every option is the same accredited test and the same report. Pick what suits you at checkout; the fee, if any, is added to either pathway price.
A quick draw at an accredited pathology collection centre near you. Usually under ten minutes. Included.
Lancet kit posted to you with an Express return satchel. If the lab cannot test your sample we send a replacement kit at no charge.
A near-painless device draws a small sample from the upper arm, with far fewer failed samples than a finger-prick. Express return satchel included.
A registered nurse comes to your home or workplace for a standard blood draw. Metro areas of capital cities; other locations on request.
Common questions
What are early warning signs of thyroid problems in women?
The common early signs are persistent tiredness, feeling cold or unusually hot, unexplained weight change, dry skin, hair thinning, constipation or loose bowels, low mood or anxiety, a racing heart, and periods that become heavier, lighter or irregular. None of them is specific, which is exactly why a blood test is the sensible next step.
What is a normal TSH level in Australia?
Most Australian laboratories use a range of about 0.4 to 4.0 mIU/L for non-pregnant adults, though the exact figures differ between labs and your report shows the range yours uses. Pregnancy has its own trimester-specific ranges. A borderline TSH is usually repeated before it is taken to mean anything.
Does a thyroid test need fasting?
No. Thyroid tests do not require fasting. A morning collection is preferred because TSH is higher in the early morning and falls during the day, so testing at a similar time makes comparisons fairer. Pause high-dose biotin supplements for about 72 hours beforehand, as they can interfere with the result.
What is the difference between TSH and a thyroid function test?
TSH is a single marker: the pituitary signal telling the thyroid what to do. A thyroid function test usually means TSH plus free T4, and sometimes free T3. This panel adds thyroid antibodies, which show whether an autoimmune process is present. If the pattern is over-active, your doctor may add a TSH receptor antibody (TRAb) test, which is not part of this panel, to look for Graves disease. More markers means fewer repeat visits when something looks off.
Can thyroid problems affect periods and fertility?
Yes. Thyroid hormones influence ovulation, so an under-active or over-active thyroid can make periods heavier, lighter, irregular or absent, and can make conceiving harder. This is why TSH is included in fertility and cycle panels as standard, and why thyroid function is checked before and during pregnancy.
How much does a thyroid function test cost without a referral?
Prices vary by provider and by how many markers are included. KnowLuna's five-marker thyroid panel is $89, with a KnowLuna doctor requesting it at no extra charge and an optional results consult for +$59. When your own GP requests thyroid tests for a clinical reason a Medicare rebate usually applies; ordering it yourself is self-pay.
Sources and further reading
- Pathology Tests Explained (RCPA): thyroid function tests
- Pathology Tests Explained (RCPA): thyroid stimulating hormone (TSH)
- Pathology Tests Explained (RCPA): free T4
- Pathology Tests Explained (RCPA): free T3
- Pathology Tests Explained (RCPA): thyroid antibodies
- Healthdirect: thyroid function tests
- Better Health Channel: thyroid gland
General information only, not medical advice. A test result is one input to a doctor's assessment, not a diagnosis on its own, and every abnormal result is followed up by a KnowLuna doctor. If your symptoms are severe or sudden, see a doctor promptly. Read our medical disclaimer.
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