TTKG Calculator

TTKG Calculator for Nephrology. No normal, high or low clinical category is reported. West's original method required nonhypotonic urine and adequate distal sodium delivery. Kamel and Halperin later explained that urea recycling causes a major uncorrectable error and stated that they do not use TTKG for dyskalemia assessment.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

Historical TTKG = (urine potassium / plasma potassium) / (urine osmolality / plasma osmolality). It attempts to adjust urine potassium concentration for water removal. All denominator measurements must be positive.

When to use this calculator

For learning why a plausible physiological calculation can have an invalid assumption, or reproducing historical arithmetic. It is not offered as a clinical test of renal potassium handling or aldosterone activity.

Inputs used

  • Urine potassium (mmol/L)
  • Paired plasma potassium (mmol/L)
  • Urine osmolality (mOsm/kg)
  • Paired plasma osmolality (mOsm/kg)

Clinical interpretation

No normal, high or low clinical category is reported. West's original method required nonhypotonic urine and adequate distal sodium delivery. Kamel and Halperin later explained that urea recycling causes a major uncorrectable error and stated that they do not use TTKG for dyskalemia assessment.

Worked example

Urine potassium 40, plasma potassium 4, urine osmolality 600 and plasma osmolality 300 give (40/4)/(600/300) = 5. Reducing urine osmolality to 150 gives 20 and also triggers a hypotonic-urine warning; neither number establishes a diagnosis.

Limitations and safety notes

Concentrated urine does not repair the urea-recycling assumption. Urine sodium is not requested because this is not a clinical eligibility workflow; it cannot be inferred from the four entered values. Do not use the result to decide potassium replacement, mineralocorticoid therapy or emergency management.

Frequently asked questions

Does meeting the original urine prerequisites validate TTKG?

No. They do not solve the later-recognized error from urea recycling.

Why keep a working calculator for a disputed method?

It supports transparent historical learning. The displayed result is expressly not a clinical classification or treatment guide.

References

  • West ML et al. New clinical approach to evaluate disorders of potassium excretion. 1986. https://pubmed.ncbi.nlm.nih.gov/3762510/
  • Kamel KS, Halperin ML. Use of Urine Electrolytes and Urine Osmolality in the Clinical Diagnosis of Fluid, Electrolytes, and Acid-Base Disorders. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8116912/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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