How to Use TTKG Calculator
- Enter serum potassium and urine potassium using the same concentration unit, usually mmol/L or mEq/L.
- Enter serum osmolality and urine osmolality. Urine osmolality must be meaningful because it adjusts for urine concentration.
- Read the TTKG value and the reference prompt. Low values suggest reduced renal potassium secretion; high values suggest increased secretion.
Formula & Theory - TTKG Calculator
TTKG Calculator uses this core formula:
TTKG = (Urine potassium / Serum potassium) ÷ (Urine osmolality / Serum osmolality)TTKG estimates the potassium gradient across the cortical collecting duct after adjusting urine potassium for water handling. The urine-to-serum potassium ratio alone can be misleading when urine is concentrated or dilute, so the osmolality ratio is used as a correction. The value is most interpretable when urine osmolality is greater than serum osmolality and distal sodium delivery is adequate. It is a physiology tool that should be paired with acid-base status, medications, kidney function, and the patient’s actual potassium level.
Use Cases for TTKG Calculator
- Evaluating whether kidneys are appropriately excreting potassium during hyperkalemia.
- Reviewing hypokalemia cases where renal potassium wasting is a concern.
- Teaching how osmolality correction changes a simple urine potassium interpretation.