Urine Thallium Unit Converter
Urine Thallium Unit Converter
Convert urine thallium between µg/L, ng/mL, nmol/L and µmol/L. Thallium poisoning is rare, acute and often forensic, and for most hospitals the assay is a send-away to a reference laboratory.
Urine Thallium converter
Mass ⇄ molarUrine thallium 2.0 µg/L, ARUP’s upper reference limit per litre
The conversion, and why thallium’s atomic weight is an interval
µg/L = nmol/L × 0.20438
µmol/L = µg/L × 0.00489285
- 204.38
- thallium’s atomic weight. CIAAW gives it as the interval [204.382, 204.385] because its isotopic composition varies in natural materials; 204.38 is the IUPAC abridged value and is what laboratories use
- 0.0015%
- the width of that interval — four hundred times inside the 0.5% a conversion check tolerates, so for any clinical purpose the ambiguity does not exist
- weeks, not days
- ARUP notes urine thallium may persist for several weeks after acute exposure, so the result cannot be used to date the ingestion
Worked example
Urine thallium 2.0 µg/L, ARUP's upper reference limit per litre
2.0 × 4.89285 = 9.8 nmol/L
= 2.0 ng/mL = 0.0098 µmol/L
At ARUP's per-litre limit, and well under its no-effect level of 5 µg/L (24.5 nmol/L); ARUP's clinical-poisoning figure of 500 µg/L is 2,446 nmol/L
Urine thallium: the figures, and a fivefold disagreement
| Source | Figure | Quantity |
|---|---|---|
| ARUP 0025019 | ≤ 2.0 µg/L | Per litre |
| ARUP 0025019 | ≤ 0.4 µg/d | Per 24 hours |
| ARUP 0025019 | ≤ 2.0 µg/g creatinine | Ratio |
| Mayo TLU, adults | < 2 µg/24 h | Per 24 hours |
| ARUP, no-effect level | < 5 µg/L | Per litre |
| ARUP, clinical poisoning | > 500 µg/L | Per litre |
What the test is actually for
| Feature | Detail |
|---|---|
| Clinical picture | Vomiting, diarrhoea and leg pain, then painful sensorimotor polyneuropathy |
| The classic sign | Alopecia, appearing one to three weeks in, long after the acute illness |
| Also described | Mees lines, optic neuritis, tachycardia, insomnia, liver injury |
| Background sources | Food, cigarette smoking, electronics manufacture; historically rodenticides |
| Availability | A referred assay for most hospital laboratories; Mayo runs it twice weekly |
A rare test, and the two numbers that disagree on it
Urine thallium in µg/L becomes nmol/L on multiplication by 4.89285, from thallium’s atomic weight of 204.38. That mass is worth a sentence, because thallium is one of the dozen or so elements whose standard atomic weight CIAAW publishes as an interval rather than a single number: [204.382, 204.385], reflecting real variation in isotopic composition between natural materials. The interval is 0.0015% wide, so for a clinical conversion it is irrelevant, and the IUPAC abridged value of 204.38 is what every laboratory uses. No published pair of thallium figures in two different unit families was found to check the mass against, so it rests on the CIAAW table alone — as the arsenic and manganese masses do, and unlike cobalt, chromium, aluminium and cyanide, each of which has a source printing the same quantity in both unit systems.
The reference figures disagree much more than the mass does. ARUP publishes three limits for the same test — 2.0 µg/L, 0.4 µg/day and 2.0 µg/g creatinine — while Mayo publishes under 2 µg per 24 hours. Mayo’s daily limit is five times ARUP’s. A 24-hour thallium of 1 µg is comfortably normal on one report and two and a half times the upper limit on the other, and a clinician holding one number has no way to know which convention produced it. ARUP separately states that concentrations below 5 µg/L are unlikely to produce adverse health effects and that those above 500 µg/L have been linked to clinical poisoning, which is a 125-fold window between "probably fine" and "poisoned".
Thallium poisoning presents as a gastrointestinal illness followed by a painful ascending sensorimotor neuropathy, and then, one to three weeks later, by alopecia — the sign that makes the diagnosis and arrives far too late to drive it. The modern cases are deliberate poisoning, contaminated herbal or illicit products, and occasional occupational exposure in electronics; the rodenticides that caused most historical cases are long withdrawn. Because thallium is excreted slowly and ARUP notes it "may persist for up to several weeks", a raised result confirms exposure but does not date it.
In practice the assay is referred out and runs on set days, so treatment decisions are made on the clinical picture. The differential for an acute neuropathy with gastrointestinal onset includes the other heavy metals — see blood arsenic and blood lead — and the toxidrome identifier for the broader pattern.
Frequently asked questions
How do I convert urine thallium from µg/L to nmol/L?
Multiply by 4.89285, from thallium’s atomic weight of 204.38. A urine thallium of 2.0 µg/L is 9.8 nmol/L. To go back, multiply nmol/L by 0.20438.
Why do Mayo and ARUP give such different thallium limits?
They do, and the gap is fivefold: Mayo publishes under 2 µg per 24 hours and ARUP 0.4 µg/day or less. A daily excretion of 1 µg is normal at Mayo and well above the limit at ARUP. Read your result against the interval your own laboratory printed, not against either of these.
What urine thallium level indicates poisoning?
ARUP states that concentrations below 5 µg/L are unlikely to produce adverse health effects and that those exceeding 500 µg/L have been linked to clinical poisoning. Mayo notes that exposed patients can excrete more than 10 µg/day. These are investigative figures, not treatment thresholds.
How long after exposure is thallium detectable in urine?
ARUP states it "may persist for up to several weeks" after an acute exposure. That makes the test useful well after the event, but it also means a raised result cannot be used to date the ingestion.
Is hair loss a reliable sign of thallium poisoning?
It is characteristic but late. Alopecia typically appears one to three weeks after exposure, by which time the gastrointestinal illness and the neuropathy have already declared themselves. Waiting for it is not a diagnostic strategy.
Related calculators
References
- ARUP Laboratories. Thallium, urine. Laboratory Test Directory 0025019; 2026. "≤0.4 microg/d", "≤2.0 microg/L" and "≤2.0 microg/g CRT"; thallium in urine "may persist for up to several weeks"; below 5 µg/L unlikely to produce adverse effects, above 500 µg/L linked to clinical poisoning.
- Mayo Clinic Laboratories. Thallium, 24 hour, urine (TLU). Test catalogue, test ID 8603; 2026. "≥18 years: <2 mcg/24 hours"; exposed patients "can have urine output greater than 10 mcg/day"; "severe and sometimes fatal sensorimotor polyneuropathy".
- Agency for Toxic Substances and Disease Registry. Toxicological Profile for Thallium. Atlanta, GA: US Department of Health and Human Services.
- Commission on Isotopic Abundances and Atomic Weights, IUPAC. Standard Atomic Weights 2024. ciaaw.org; accessed October 2026. As 74.921595(6), Mn 54.938043(2), Al 26.9815384(3), Cr 51.9961(6), Co 58.933194(3), Tl [204.382, 204.385]; for the interval elements the IUPAC abridged values Tl 204.38, C 12.011, N 14.007 are used.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/