Urine Potassium Unit Converter
Urine Potassium Unit Converter
Urine potassium asks whether the kidney is the route of a potassium loss, not whether the body has enough. Convert mmol/L, mEq/L, mg/dL and mg/L, spot or timed.
Urine Potassium converter
Monovalent — mmol/L = mEq/LSpot urine potassium 55 mmol/L in a hypokalaemic patient, before replacement
Formula and conversion factors
mg/dL = mmol/L ÷ 0.255766
mEq/L = mmol/L (potassium is monovalent)
K:creatinine (mmol/mmol) = urine K in mmol/L ÷ urine creatinine in mmol/L
- 0.255766
- derived from the atomic weight of potassium, 39.0983 — the same factor as on the serum potassium page
- mmol/L = mEq/L
- potassium carries one charge, so the two units are the same number
- ratio, not concentration
- the concentration is diluted or concentrated by water handling, so the clinically useful form is the ratio to creatinine on the same sample
Worked example
Spot urine potassium 55 mmol/L in a hypokalaemic patient, before replacement
55.0 mmol/L — and 55.0 mEq/L, the same number
55 ÷ 0.255766 = 215.0 mg/dL = 2,150 mg/L
With a urine creatinine of 10 mmol/L the ratio is 5.5 mmol/mmol, well above Halperin's 1.5 — the kidney is wasting potassium, not conserving it
The same 55 mmol/L in a dilute sample would mean a much lower excretion rate
Spot urine potassium converted
| mmol/L (mEq/L) | mg/dL | mg/L |
|---|---|---|
| 10.0 | 39.1 | 391 |
| 20.0 | 78.2 | 782 |
| 55.0 | 215.0 | 2,150 |
| 100.0 | 391.0 | 3,910 |
Figures a urine potassium is read against
| Source and basis | Figure | Unit |
|---|---|---|
| Mayo KUR, 24-hour, adults 18 and over | 16 – 105 | mmol/24 h |
| ARUP ULYTE, 24-hour collection | 25 – 125 | mmol/day |
| Mayo, random urine potassium (RKUR) | No established reference values | — |
| ARUP, random urine electrolytes (ULYTE) | Not established for random urines | — |
| Halperin, kidney conserving potassium (spot ratio) | Below 1.5 | mmol/mmol |
| Halperin, kidney conserving potassium (timed) | Below 15 | mmol/day |
Where the potassium went
A serum potassium tells you whether the patient is in danger. A urine potassium tells you where the potassium went, and it is only interpretable alongside the serum value. The question it answers is binary: in a hypokalaemic patient, is the kidney conserving potassium as it should — in which case the loss is gastrointestinal, or the potassium has shifted into cells — or is it still excreting potassium, which makes the kidney itself the route of loss. For the blood side of the pair, use the serum potassium unit converter.
Potassium is monovalent, so mmol/L and mEq/L are the same number, and the conversion to mass units uses 10/39.0983: mmol/L is mg/dL × 0.255766. Milligrams are worth knowing because supplement and dietary labels use them — 55 mmol/L of urine potassium is 215.0 mg/dL — but no laboratory reports a urine potassium that way.
The concentration on its own is close to uninterpretable, and both reference laboratories say so: Mayo records “no established reference values” for a random urine potassium, and ARUP states intervals are not established for random urines. The reason is dilution. A urine potassium of 55 mmol/L in a concentrated morning sample and 20 mmol/L after a litre of water can represent the same excretion rate. The accepted fixes are to divide by the creatinine on the same sample — Halperin’s threshold is a potassium-to-creatinine ratio under 1.5 mmol/mmol for an appropriately conserving kidney — or to calculate the fractional excretion of potassium. The transtubular potassium gradient was the older approach and is now largely abandoned.
Two traps. The first is timing: take the urine while the patient is still hypokalaemic and before replacement, because potassium given by any route appears in the urine within hours and turns a conserving kidney into a wasting one on paper. The second is the 24-hour collection, where Mayo gives 16 to 105 mmol/24 h and ARUP 25 to 125 mmol/day; those intervals describe dietary potassium intake in a reference population and say almost nothing about tubular function in a patient who is not eating normally.
Frequently asked questions
Is urine potassium in mmol/L the same as mEq/L?
Yes — potassium is monovalent, so one millimole is one milliequivalent. A report of 55 mmol/L and one of 55 mEq/L are the same result.
How do I convert urine potassium from mmol/L to mg/dL?
Divide by 0.255766, the factor derived from potassium’s atomic weight of 39.0983. A urine potassium of 55 mmol/L is 215.0 mg/dL. Milligrams appear on dietary and supplement labels, not on laboratory reports.
What is a normal spot urine potassium?
There is no established interval — Mayo and ARUP both say so in their catalogues. The concentration depends on how dilute the urine is. Use the potassium-to-creatinine ratio or the fractional excretion of potassium instead, interpreted against the serum potassium.
What urine potassium means the kidney is conserving it?
In a hypokalaemic patient, a spot potassium-to-creatinine ratio below about 1.5 mmol/mmol, or a 24-hour potassium below about 15 mmol/day, indicates an appropriate renal response — so the loss is extrarenal or the potassium has shifted into cells.
Does potassium replacement affect the result?
Yes, substantially. Replacement potassium is excreted within hours, so a sample taken afterwards can look like renal potassium wasting in a patient whose kidneys were conserving perfectly. Take the urine before replacement where that is possible.
Related calculators
References
- Mayo Clinic Laboratories. Potassium, 24 hour, urine (KUR) — reference values. Test catalogue, test ID 614060; 2026.
- Mayo Clinic Laboratories. Potassium, random, urine (RKUR) — reference values and interpretation. Test catalogue, test ID 610696; 2026.
- ARUP Laboratories. Electrolytes, urine (ULYTE) — reference intervals for sodium, potassium and chloride per 24 hours. Laboratory Test Directory 0020498; 2026.
- Halperin ML. Assessing the renal response in patients with potassium disorders: a shift in emphasis from the TTKG to the urine K+/creatinine ratio. Afr J Nephrol. 2017;20(1):22–24.
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/