Thyroid Lab Results, Explained

A full thyroid panel is TSH, free T4, free T3 and thyroid antibodies (TPO and thyroglobulin). Reverse T3 is useful when symptoms continue despite normal results.

TSH alone shows how hard your brain is asking the thyroid to work, but not how much active hormone actually reaches your cells.

TSH is a sensitive first screen, and guidelines use it to find most thyroid problems. But it can be normal while free T3 is low or antibodies are rising, so a TSH-only test can miss what explains your symptoms.

Usually 6 to 8 weeks after starting or changing a dose, then every 6 to 12 months once your levels and symptoms are stable. Test sooner if symptoms change, during pregnancy, or if you start or stop a medication that affects thyroid hormone.

Yes. Paloma’s at-home kit measures TSH, free T4, free T3 and TPO antibodies from a few drops of blood from a finger prick, with reverse T3 and vitamin D as add-ons. It costs $119, or $75 for members, and results arrive 2 to 5 business days after the lab receives your sample.

Dried blood spot testing has been used for decades, and modern lab methods measure thyroid hormones accurately from a few drops. For tracking your levels over time, the most important thing is to use the same type of test, at the same time of day, each time.

Not with Paloma. You can order the at-home kit or a Quest lab panel online, and an independent clinician reviews each lab order. No insurance or doctor visit is needed.

Insurance often covers thyroid tests ordered by your doctor as part of a visit. Paloma’s at-home kit and online Quest panels are paid directly, with clear prices upfront; the Quest panels are HSA and FSA eligible.

No. Thyroid tests aren’t affected by food. Fast only if the same order includes tests that need it, such as glucose or cholesterol.

For a blood draw at a lab, take your dose after the draw, especially if it contains T3 (NDT, liothyronine), which can raise free T3 for a few hours. Paloma’s at-home kit uses an assay where you don’t need to delay your medication.

It can. Biotin, common in hair, skin and nails supplements and multivitamins, interferes with many lab methods and can make TSH read falsely low and free T4 and T3 falsely high. For a lab draw, stop it 3 days before. Paloma’s at-home kit uses an assay where you don’t need to stop supplements.

Morning is best, and the same time each time matters most. TSH is highest in the early morning and falls during the day, so testing at different times can make your results look like they changed when they didn’t.

Most US labs use a range of about 0.4 to 4.5 mIU/L. Many thyroid-focused clinicians aim for 0.5 to 2.5 mIU/L, where most people feel their best. Your lab report prints its own range, which is the one to compare against.

A lab’s normal (reference) range covers 95% of a tested population, which includes people with early or untreated thyroid problems. An optimal range is narrower: the levels where most people have the fewest symptoms. Being in the normal range doesn’t always mean being in the range where you feel well.

Your levels may be normal but not optimal for you, you may not be converting T4 into active T3 well, or antibodies may show early Hashimoto’s before TSH changes. Other causes, like low iron, vitamin D, sleep or perimenopause, can also look like thyroid symptoms. A clinician who looks at the full panel and your symptoms can tell these apart.

This is often called subclinical hypothyroidism: the thyroid needs extra push from TSH to keep hormone levels normal. It’s common, especially with Hashimoto’s. Clinicians usually retest in 6 to 12 weeks with antibodies, and consider treatment based on how high TSH is, your symptoms, and plans for pregnancy.

Free T3 is the active thyroid hormone. A low or low-normal free T3, especially with a normal free T4, can mean your body isn’t converting T4 to T3 well. Stress, illness, calorie restriction, low iron or selenium, and some medications can play a part.

Reverse T3 is an inactive form your body makes from T4 instead of active T3, usually more of it during stress, illness or calorie restriction. It isn’t used to diagnose hypothyroidism, but alongside free T3 it can help explain symptoms when other results look normal.

TPO antibodies show your immune system is targeting the thyroid, the hallmark of Hashimoto’s, the most common cause of hypothyroidism in the US. They often appear years before TSH changes, so they’re a reason to monitor your thyroid regularly, even if your levels are normal today.

Yes, in a minority of people. Some have only thyroglobulin antibodies, and some have none despite Hashimoto’s changes on a thyroid ultrasound. That’s why testing both antibodies, and sometimes an ultrasound, can help.

Labs use different methods and set their own ranges, so the same blood can give slightly different numbers. Compare each result against the range printed on that lab’s report, and use the same lab for tracking over time.

US labs report free T4 in ng/dL and free T3 in pg/mL; many other countries use pmol/L. The numbers look very different but mean the same thing. Our unit converter switches between them.

Most clinicians aim for a TSH in the lower half of the normal range on treatment. Paloma’s clinicians generally aim for about 0.5 to 2 mIU/L, adjusted for your age, symptoms and health history.

Medications containing T3, like Armour Thyroid, NP Thyroid or liothyronine, can lower TSH, especially if you take your dose shortly before the blood draw. A TSH below 0.4 is still worth reviewing with your prescriber, because a dose that’s too high can affect your heart and bones over time.

After 6 to 8 weeks. Thyroid hormone levels take that long to settle on a new dose, so testing earlier can be misleading.

No. Bring your results to your prescriber. Dosing depends on your symptoms, age, heart health and other medications as well as your labs.