Free T4
What it measures
Reported in ng/dL on Indian reports and pmol/L internationally. Free T4 is the more informative of the two thyroxine tests in most situations, because it is unaffected by the carrier-protein changes that move total T4 around. Note that free T4 and total T4 are different tests: putting them on one trend line compares two different measurements.
Reading it in a different unit
This lab reports Free T4 in ng/dl. Reports from other labs — especially ones using European or US-style formatting — sometimes use a different unit for the same measurement. The relationship between them:
| Reported unit | How it relates to ng/dl |
|---|---|
| pmol/l | ng/dl = pmol/l × 0.077687 |
Unit conversions verified against published molar masses and LOINC definitions. This is not a diagnostic reference — the normal range for any test is set by the laboratory that ran it and printed on your report.
Why this matters for tracking a trend
A value plotted next to earlier results only tells you something if every point is on the same scale. Two readings of the same test from two different labs, in two different units, can look like a dramatic change when nothing about your actual result changed — only the unit did. Converting to one scale before comparing is what keeps a trend line honest.
LOINC code for this test: 3024-7.
General information about laboratory measurement, not medical advice. Whether a specific result is normal for you depends on your lab's reference range, your history and your doctor's judgement — not on this page.