Transtubular Potassium Gradient (TTKG)
Assesses renal potassium handling to differentiate causes of hyperkalemia and hypokalemia
- Highest activation tier
- Recommended
- How it is scored
- Scored in code; a stated value is compared only from the structured summary or a supplied value
- Care settings
- ICU, Inpatient
When it activates
Scribeable activates a calculator from the encounter. The Transtubular Potassium Gradient (TTKG) can activate when the transcript or pasted chart context documents any of these:
- Hyperkalemia workup
- Hypokalemia workup
- Differentiating renal vs extrarenal potassium disorder
- Potassium wasting evaluation
- Aldosterone activity assessment
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: E87.5, E87.6.
Inputs the note needs
4 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; at this calculator’s tier a missing input is never requested, and a missing required input keeps the score out of the draft.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| Urine potassium (mEq/L) | lab | mEq/L | |
| Serum potassium (mEq/L) | lab | mEq/L | |
| Urine osmolality (mOsm/kg) | lab | mOsm/kg | |
| Serum osmolality (mOsm/kg) | lab | mOsm/kg |
Scoring
TTKG = (Urine K / (Urine Osm / Serum Osm)) / Serum K. Normal 4-8 on normal diet.
TTKG = (Urine potassium (mEq/L) × Serum osmolality (mOsm/kg)) / (Serum potassium (mEq/L) × Urine osmolality (mOsm/kg))
Interpretation
Normal diet: TTKG 4-8. In hyperkalemia: TTKG <7 suggests impaired renal K excretion (renal cause — hypoaldosteronism, medication effect). In hypokalemia: TTKG >4 suggests renal potassium wasting. Requires urine osmolality > serum osmolality for valid interpretation.
Evidence
Sources carried in Scribeable's citation registry for this calculator; guideline version: Ethier JH et al. 1990.
- Ethier JH et al. The transtubular potassium concentration in patients with hypokalemia and hyperkalemia (TTKG)Ethier et al. (TTKG) 1990 · 1990 · link last verified 2026-03-28
How Scribeable handles it in the note
When an encounter activates the Transtubular Potassium Gradient (TTKG) (its highest tier is recommended), Scribeable does not ask you for missing inputs. The score is computed in code from whatever inputs resolve from the transcript, the pasted chart context or charted labs; a computed value is written into the draft only when every required input already resolves.
The score is computed in code from the resolved inputs, not recalled by the language model. A stated Transtubular Potassium Gradient (TTKG) value is compared against the computed one when the draft's structured summary carries it; a disagreement found there is flagged to the second drafting pass, which is instructed to correct the score and its interpretation, unless Scribeable has supplied the computed value to that pass, in which case the value the draft writes is checked against the supplied one and a detected difference is shown beside the note for you to adjudicate rather than silently rewritten.
Classified as a deterministic formula: a spare suggestion is easy to ignore, so activation is permissive.
See it activate on your own encounter
14 days of full Pro. No sales call.
14-day Pro trial with a card on file. $79/month starts 14 days after your trial begins unless you cancel first. Cancel any time from Settings > Billing.