What is a normal sodium-to-potassium ratio?

Based on standard human serum reference ranges (sodium 135–145 mEq/L and potassium 3.5–5.0 mEq/L), the normal serum Na/K ratio mathematically ranges from 27 to 42 (averaging around 30–35). Values within this range reflect balanced electrolyte concentrations.

What does a low Na/K ratio indicate?

A ratio below 27 indicates relative hyponatremia, hyperkalemia, or both. In veterinary medicine, a ratio < 27 is a classic screening clue for canine hypoadrenocorticism (Addison's disease). In humans, low ratios may reflect renal dysfunction, severe illness, or mineralocorticoid deficit, but diagnosing human Addison's disease requires ACTH stimulation and cortisol testing.

What does a high Na/K ratio indicate?

A high ratio (above 42) reflects elevated sodium relative to potassium. Common causes include hypokalemia (diuretic use, gastrointestinal losses), hypernatremia (dehydration, sodium retention), or inadequate dietary potassium intake.

Are the units mEq/L or mmol/L?

Both units are numerically equivalent for sodium and potassium (1 mEq/L = 1 mmol/L for monovalent ions), so you can use either without conversion. Use whatever your lab report shows.

Is this tool a substitute for clinical diagnosis?

No. This calculator is for educational and reference use only. All electrolyte results must be interpreted in the full clinical context by a qualified healthcare professional.

Sodium Potassium Ratio

Enter serum sodium and potassium values to calculate the Na/K ratio and get an instant clinical interpretation.

Serum Lab Values

Serum Sodium (Na⁺) mEq/L or mmol/L

Normal range: 135–145 mEq/L

Serum Potassium (K⁺) mEq/L or mmol/L

Normal range: 3.5–5.0 mEq/L

Reference Ranges

Na/K Ratio	Interpretation
< 27	Low — relative hyponatremia or hyperkalemia
27–42	Normal (derived from Na 135–145, K 3.5–5.0)
> 42	High — possible hypokalemia or hypernatremia

Enter values and click Calculate to see your result.

Summary

The serum sodium-to-potassium (Na/K) ratio is calculated by dividing serum sodium by serum potassium, both expressed in mEq/L or mmol/L. Based on standard human serum lab reference intervals (sodium 135–145 mEq/L, potassium 3.5–5.0 mEq/L), a normal ratio mathematically spans 27 to 42. A low ratio (< 27) suggests relative hyponatremia or hyperkalemia; while Na:K < 27 is a classic veterinary screening index for canine Addison's disease, human adrenal insufficiency requires definitive cortisol and ACTH testing. A high ratio (> 42) indicates hypokalemia or hypernatremia.

How it works

Enter your serum sodium (Na+) value in mEq/L or mmol/L.
Enter your serum potassium (K+) value in mEq/L or mmol/L.
The calculator divides Na by K to produce the ratio.
The result is compared against the standard reference range (27–42).
An interpretation is shown indicating low, normal, or high status with clinical context.

Use cases

Evaluating relative sodium and potassium proportions from routine basic metabolic panels.
Assessing electrolyte balance in patients with dehydration, diuretic therapy, or fluid shifts.
Understanding physiological electrolyte ratios in human serum (normal reference range 27–42).
Quick bedside review of electrolyte lab results for clinicians, veterinary staff, and students.
Tracking serial Na/K ratios over time in patients with chronic electrolyte or renal disorders.
Educational reference for understanding how sodium and potassium homeostasis interact.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu