Urine Electrolyte Calculator

Urine Potassium

24 hr Urine potassium (Valuable if UNa>100 mEq/day): Avoid in patients with severe hypokalemia, as it may delay treatment.

<15 mEq/day suggests extra renal loss.
>30 mEq/day suggests renal loss.

Random Urine Potassium (Simple)

<15 mEq/L suggests extra renal loss.
>15 mEq/L suggests renal loss.

FENa

Sodium

Creatinine

UAG = Na urine + K urine - Cl urine

Na urine

K urine

Cl urine

Urine osmolality = Urine 2(Na + K) + Urea + Glucose (in mmol/L)

Sodium (mmol/L)

Potassium (mmol/L)

Urea (mmol/L)

Glucose (mmol/L)

Measure urine osmolality

mmol/L = mg/dl / 18

Comment

If FENa < 1%, consider pre-renal causes, such as hypovolemia, heart failure, and renal artery stenosis.

If FENa is greater than 2%, consider intrinsic renal causes, pre-renal azotemia due to diuretic use, renal salt wasting, mineralocorticoid deficiency, or metabolic alkalosis.

Contrast-induced nephropathy, non-oliguric acute tubular necrosis (ATN), the use of ACE inhibitors or angiotensin receptor blockers (ARBs), rhabdomyolysis, sepsis, and hemolysis may occur with a fractional excretion of sodium (FENa) < 1%.

Comment

If FEUrea < 35%, consider pre-renal causes.

If FEUrea > 50%, consider intrinsic renal causes.

Comment

Note that TTKG is valid only when UNa >25 mEq/L

- TTKG is sometimes criticized for being inaccurate, particularly in the evaluation of hyperkalemia.

TTKG values between 8 and 9 are considered normal in patients with a normal diet.
During hyperkalemia (K⁺ >5.0 mEq/L), the TTKG should be ≥7; lower values suggest hypoaldosteronism.
During hypokalemia (K⁺ <3.5 mEq/L), the TTKG should be <3; greater values suggest renal potassium wasting.
Expected TTKG in hyperkalemia is >10, which suggests normal renal excretion of potassium.

Comment

This UAG can help differentiate the causes of a non-gap metabolic acidosis.

- If UAG is positive, consider renal causes of acidosis, e.g. RTA

- If UAG is negative, consider extra renal causes of acidosis, e.g., diarrhea.

Limitation:

- Another negative charge in urine, such as ketone, hippurate, salicylate, and unabsorbable anion.

- UAG may be positive in DKA.

Comment

This gap can provide important insights into the presence of unmeasured solutes in the urine, which can be crucial for diagnosing various metabolic and renal disorders.

Normal osmolal gap: Typically less than 10 mOsm/kg
Increased osmolal gap: May indicate the presence of unmeasured solutes such as alcohols, sugars, or other substances