The bands on this page
| Result | What it is called here |
|---|---|
| under 15 | Low — poor conversion, check energy intake & stress |
| 15 to 20 | Borderline |
| over 20 | Good conversion |
What goes in, and where each number comes from
Every input is a real test. Follow one to see its normal range, its optimal range and what moves it — the calculation is only as good as the numbers you feed it.
What it costs to actually get these numbers
| The 2 tests on their own | $58.50 |
| The cheapest panel that covers them — On Thyroid Hormone or a Thyromimetic (9 markers) | $133.20 |
Prices are Marek Diagnostics with the 10% code already applied, and they are what was filed when this page was built — check the cart. Ordering through these links pays a commission at no cost to you.
What could have moved the measurement, not the marker
A wrong number and a real change look identical on a report. These are the reasons a result here can be an artifact of how the blood was drawn or run, and they are worth ruling out before anything else.
Biotin interferes with the streptavidin-biotin immunoassays most hormone tests run on. Depending on the assay design it pushes the result falsely HIGH or falsely LOW — there is no single direction to correct for. Hair, skin and nail products are the usual source, and doses in those are far above the RDA.
What to do: Stop biotin 48–72 hours before the draw, and check every supplement label rather than just the one labeled biotin.
All inhibit the deiodinase that converts T4 to T3, pushing more down the reverse T3 path.
What to do: Note any of these — the raised rT3 is the drug, not your thyroid.
Falls first and furthest when calories are short — this is an adaptation to under-eating, not thyroid disease, and it happens before TSH moves at all.
What to do: Interpret against your actual intake and training load, not against the reference range alone.
This is an acute-phase reactant — it moves substantially during any infection, injury or inflammatory episode, and the change has nothing to do with your baseline.
What to do: Wait two weeks after any illness, vaccination or injury before drawing or interpreting.
1 more interferences are listed on the marker pages themselves: Free T3 (Triiodothyronine) · Reverse T3.