$4.00
Priced per marker, with baseline labs included. You’ll see your total before you pay.
Thyroid
T3 uptake test
Older measure used to derive Free Thyroxine Index; largely replaced by direct Free T4.
At a glance
In about 5 days
Most results are ready in about 5 days. Some specialty markers can take up to 21 days.
Check before your draw
This marker has no preparation tag, but it can still need preparation. Contact us before your draw if you’re not sure.
Walk in at Quest
Your lab order arrives by email. Most Quest locations take walk-ins, so bring it with a photo ID.
What it measures
Despite its name, this test doesn’t measure T3 itself. It’s an older test that shows how much open space is left on the proteins that carry thyroid hormone, and it’s used with total T4 to estimate free thyroid hormone.
Why it matters for women
Pregnancy, birth control pills and menopause hormone therapy with estrogen can raise the proteins that carry thyroid hormone, which can lower this result even when your thyroid works normally. That’s why it’s read alongside other thyroid tests. Most doctors now use a direct free T4 test instead.
You might check it if…
- a doctor asked for it alongside a total T4 test
- you take estrogen and your thyroid results seem confusing
What your result may mean
High T3 uptake: what it may mean
High T3 uptake may suggest fewer open spots on the proteins that carry thyroid hormone. It can happen with low thyroid-binding globulin (TBG), the main carrier protein, as with steroids or androgens, or with an overactive thyroid (hyperthyroidism). Severe illness can sway it as well. If your thyroid is overactive, you may notice a racing heart, sweating or weight loss. This older test can’t stand alone, so a clinician may use it with total T4 or look at a direct free T4 test.
Low T3 uptake: what it may mean
Low T3 uptake may suggest more open spots on the proteins that carry thyroid hormone. It can happen with estrogen, including pregnancy, birth control pills and menopause hormone therapy, even when your thyroid works normally. An underactive thyroid (hypothyroidism) can lower it too. If your thyroid is underactive, you may notice tiredness, feeling cold or weight gain, but with estrogen you may feel nothing unusual. This result can be read with total T4, or a clinician may prefer a direct free T4 test.
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These notes provide context and do not diagnose a condition. Not yet available in NY, NJ, RI, HI, ND, SD or WV.