Transtubular Potassium Gradient (TTKG)
TTKG = (Urine K / Plasma K) ÷ (Urine osmolality / Plasma osmolality). Use simultaneous spot samples; teaching cutoffs are approximate.
Calculator
How it works
TTKG is a teaching index relating urine and plasma potassium and osmolality to infer distal tubular potassium handling; many sources use cutoffs near 3 and 7 with important exceptions.
Limits
Invalid with low urine flow, osmotic diuresis, severe CKD, acid–base disturbances, or non-steady-state collections; does not replace endocrine testing or specialist evaluation.
Educational tool only—not for diagnosis or treatment decisions.