Transtubular Potassium Gradient Calculator

Enter urine and serum potassium and osmolality to compute the TTKG.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

The transtubular potassium gradient (TTKG) estimates how much the kidney's collecting duct is concentrating potassium relative to what arrives at that point, correcting for water reabsorption along the way. It is calculated as TTKG = (urine K⁺ ÷ (urine osmolality ÷ serum osmolality)) ÷ serum K⁺ — the osmolality ratio adjusts urine potassium for how much water has been reabsorbed, so the result reflects tubular potassium handling rather than simple urine concentration.

This calculator takes urine potassium, serum potassium, urine osmolality, and serum osmolality and returns the TTKG. Nephrologists and internal medicine physicians use it at the bedside to help distinguish renal from extrarenal causes of an abnormal serum potassium — for example, whether hyperkalemia reflects reduced aldosterone activity or the kidneys are responding appropriately to a non-renal cause.

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