The TTKG reflects how strongly aldosterone is driving potassium into the urine. In low potassium, a TTKG below 3 points to non-kidney losses; above 7 suggests kidney losses. In high potassium, a TTKG below 7 suggests too little aldosterone effect.
How to use the TTKG Calculator
- Urine potassium
- Plasma potassium
- Urine osmolality
- Plasma osmolality
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter urine and plasma potassium and osmolality from samples taken together. The test is less used today because of its assumptions; the urine potassium-to-creatinine ratio is an alternative.
Inputs explained
| Field | What to enter |
|---|---|
| Urine potassium | In mEq/L |
| Plasma potassium | In mEq/L |
| Urine osmolality | In mOsm/kg |
| Plasma osmolality | In mOsm/kg |
Example values
How the main result changes when Urine potassium changes and everything else stays at the example values above:
| Urine potassium (mEq/L) | TTKG |
|---|---|
| 20 | 3.9 |
| 30 | 5.8 |
| 40 | 7.7 |
| 50 | 9.7 |
| 60 | 11.6 |
| 80 | 15.5 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
TTKG = (urine K ÷ plasma K) ÷ (urine osmolality ÷ plasma osmolality)
Valid when urine osmolality > plasma osmolality and urine Na > 25 mEq/L
Worked example
Inputs — Urine potassium: 40 mEq/L; Plasma potassium: 3 mEq/L; Urine osmolality: 500 mOsm/kg; Plasma osmolality: 290 mOsm/kg.
Results — TTKG = 7.7; Interpretation = Low K with TTKG > 7 – renal potassium wasting likely; Test valid? = Yes.
Key terms
- TTKG
- Transtubular potassium gradient.
Frequently asked questions
What is a normal TTKG?
About 8–9 on a normal diet; above 10 with high potassium intake.
Why is the TTKG less used now?
Urea recycling makes its assumptions unreliable; many experts prefer the urine K/creatinine ratio.
What causes a low TTKG with high potassium?
Hypoaldosteronism or drugs such as ACE inhibitors and potassium-sparing diuretics.