Transtubular Potassium Gradient (TTKG)
TTKG Calculator
mEq/L
mEq/L
mOsm/kg
mOsm/kg
Score:–
–
–
May help in assessment of hyperkalemia or hypokalemia.
When to Use
Patients with hyper- or hypokalemia (defined as K + <3.5 or >5.0 mEq/L in this calculator).
Formula
TTKG = (urine potassium / serum potassium) / (urine osmolality / serum osmolality)
Pearls / Pitfalls
TTKG is sometimes criticized for being inaccurate, particularly in the evaluation of hyperkalemia.
Advice
Use clinical judgment in correcting hyper- or hypokalemia, and as always, never rely solely on a calculator to make decisions.
More Information
Interpretation: 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.