Urine Potassium, 24-Hour
The total potassium that left your body in urine over 24 hours, which mostly follows how much potassium you eat.
AI-verified against cited sources. Awaiting expert reviewAlso called U K 24h, UK 24h, 24h UKLOINC 2829-0
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What it is
Potassium is a mineral that helps your nerves, muscles and heart work. Most of it sits inside your cells, and your kidneys remove any extra in urine. This test adds up all the potassium in the urine you collect over a full day. In a steady state the total follows how much potassium you take in from food. It also helps show whether your kidneys are holding on to potassium or letting it go.
Why it matters
When blood potassium is too low or too high, this test helps show whether the kidneys are involved or whether the cause is somewhere else, such as low intake or losses from the gut. It also gives a picture of how much potassium you eat. The World Health Organization says an intake of at least 90 mmol (3,510 mg) a day may be beneficial for adults. People with kidney disease or on some blood pressure medicines may need a different target, so ask your clinician.
If it’s low
A low total usually means you ate little potassium, or that your kidneys held on to it because you lost potassium another way, such as through diarrhea. Some medicines and low aldosterone can also lower it. When blood potassium is low and the urine total is under about 30 mmol (30 mEq) a day, Mayo explains that this suggests the kidneys are holding on to potassium appropriately and the cause lies elsewhere, such as low intake or gut losses.
Common causes
- Low potassium intake
- A collection that missed some urine
- Diarrhea or laxative use
- Poor absorption of food in the gut (malabsorption)
- Some medicines, including ACE inhibitors, ARBs, beta blockers, NSAIDs, lithium, trimethoprim and potassium-sparing diuretics
- Too little aldosterone (hypoaldosteronism)
What can help
- Think back over the collection day and tell your clinician if any urine was missed
- Ask your clinician whether your diet, digestive symptoms or medicines could explain it
If it’s high
A high total most often means you ate a lot of potassium, from foods like fruit, vegetables and beans, or from supplements and salt substitutes. Water pills can also make the kidneys release more potassium. Less often, a hormone called aldosterone is too high, or the kidneys are losing potassium. Your clinician reads it alongside your blood potassium.
Common causes
- Eating plenty of potassium-rich foods
- Potassium supplements or potassium-based salt substitutes
- Water pills (loop and thiazide diuretics)
- Dehydration
- Too much aldosterone from the adrenal glands (primary aldosteronism)
- Low blood magnesium
- Diabetic ketoacidosis or other forms of acidosis
- Damage to the kidney tubules (acute tubular necrosis)
- Muscle breakdown (rhabdomyolysis)
- Eating disorders
- Overdose of aspirin-type medicines (salicylates)
What can help
- Ask your clinician how your urine result compares with your blood potassium
- Review your diet, supplements and salt substitutes with your clinician
- Ask whether any of your medicines could be affecting the result
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 25–125 mmol/24 h. Source: ARUP Laboratories, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine), Mayo Clinic Laboratories, Quest Diagnostics.
- 18+ (this one applies)25–125 mmol/24 h
Sources: ARUP Laboratories, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine), Mayo Clinic Laboratories, Quest Diagnostics
What can affect your result
- Potassium in food, supplements and salt substitutes
- Water pills and other medicines
- Diarrhea, vomiting, sweating and how much you drank
- Kidney function
- Collection accuracy: missed or extra urine changes the total
- Day-to-day variation: one day is a snapshot of your usual intake
- Incomplete or over-long collections give a falsely low or high total. Labs record the total volume and collection time, and some also check urine creatinine to judge whether the collection was complete.
- Medicines change potassium in urine, including water pills, ACE inhibitors, ARBs, beta blockers, NSAIDs, lithium, trimethoprim and potassium-sparing diuretics. Tell your clinician about every medicine and supplement you take.
- Potassium supplements and potassium-based salt substitutes raise the total.
- Diarrhea, laxative use, heavy sweating or dehydration during the collection can shift the result.
- Mayo accepts several preservatives for this test but not toluene or nitric acid. Use the container your lab gives you.
A full 24-hour collection. Empty your bladder at a set time and flush that urine, then collect all urine after that, including the first urine at the same time the next day. The total reflects the day you collected, and it follows what you ate and drank around that day.
When to talk to a clinician
A urine potassium result alone is not an emergency. Contact your clinician promptly if your blood potassium was flagged by the lab, or if you have muscle weakness, cramps, or a pounding, skipping or very slow heartbeat. Call 911 or your local emergency number for chest pain, fainting or trouble breathing.
Questions you could ask
- How does this result fit with my blood potassium and kidney tests?
- Does this match how much potassium I get from food and supplements?
- Could any of my medicines be involved?
- Could my diet, digestive symptoms or a medicine explain this?
- Was my collection complete, and should we repeat it?
Questions people ask
Does this test tell me how much potassium I eat?
Roughly. Most of the potassium you eat leaves in your urine, so the daily total follows your intake. Kidney disease, water pills and some other medicines change how much leaves in urine, so it is not exact.
How do I turn mmol of potassium into milligrams?
Multiply by 39.1. A result of 90 mmol is about 3,500 mg of potassium. For potassium, 1 mmol equals 1 mEq.
My blood potassium is off. Why would my clinician want a urine test too?
The urine total helps show whether the kidneys are losing potassium or holding on to it. That points toward different next steps, such as looking at diet, digestive losses, hormones or medicines.
Show the science and sources
Units
- 1 mmol/24 h = 1 mmol/24 h
- 1 mmol/24 h = 1 mEq/24 h
- 1 mmol/24 h = 39.1 mg/24 h
Open the Urine Potassium 24h unit converter
Is a change real?
Urine Potassium 24h naturally varies about 24.4% from test to test in the same healthy person. Between two results from the same lab, a rise of 111% or more, or a fall of 53% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Desirable Biological Variation Database specifications, 2014 update (Minchinela J, Ricos C, et al.; the 'Ricos database', a compilation of median published CVI/CVG).
For clinicians and researchers
Potassium is the major intracellular cation (intracellular concentration about 20 times the extracellular level, with only about 2% of body potassium in plasma), and the kidney is the main regulator, with most filtered potassium reabsorbed proximally and urinary excretion set mainly by secretion in the distal nephron. In a steady state, urinary excretion follows intake. Mayo's interpretive comment for hypokalemia: 24-hour urinary excretion below 30 mEq suggests appropriate renal conservation (low intake or extrarenal loss), while excretion above 30 mEq indicates the kidneys are the source of the loss. Measured by ion-selective electrode (Quest), which is selective but not specific: other monovalent cations may interfere, but not in the physiologic range (Mayo). Published intervals: ARUP 25–125 mmol/d, MedlinePlus 25–125 mEq per day, Quest 22–160 mmol/24 h, and Mayo 16–105 mmol/24 h for adults (none established under 18). 1 mmol of potassium is 39.10 mg, and 1 mEq equals 1 mmol. WHO recommends a potassium intake of at least 90 mmol/day (3,510 mg/day) for adults. Quest lists increased excretion in primary aldosteronism, dehydration and salicylate toxicity, and decreased excretion in malabsorption. MedlinePlus adds metabolic acidosis, low magnesium, rhabdomyolysis and tubular damage as causes of high excretion. Collection completeness is the main source of error, so check total volume, collection time and urine creatinine. For a single sample, see Urine Potassium, Random.
LOINC 2829-0 (primary), 51720-1, 21476-7. Specimen: urine-24h.
Sources
- Potassium, Urine (test 0020849), ARUP Laboratories
- Potassium urine test, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine)
- KUR - Potassium, 24 Hour, Urine, Mayo Clinic Laboratories
- Potassium, 24-Hour Urine without Creatinine (test code 11316), Quest Diagnostics
- Healthy diet (fact sheet), World Health Organization
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.