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Corrected Potassium Calculator

Enter the measured potassium and arterial pH to get the pH-corrected potassium.

How it is calculated

The tool moves a measured potassium to what it would be at the reference pH of 7.4: K_corrected = K + 0.6 × ((pH − 7.4) ÷ 0.1). K is the measured serum potassium in mEq/L and pH is the arterial pH from the same sample. The pH offset, pH − 7.4, is shown too. Each 0.1 pH unit away from 7.4 shifts the potassium by 0.6 mEq/L, and the direction follows the sign: a pH below 7.4 gives a negative offset and lowers the corrected value, a pH above 7.4 raises it. Both inputs must be above zero. The factor of 0.6 is a rough bedside rule, not an exact constant, so the result is an estimate to read together with the clinical picture.

Worked example

A blood sample shows potassium 5.8 mEq/L at an arterial pH of 7.2. The offset is 7.2 − 7.4 = −0.20, which is two steps of 0.1. The adjustment is 0.6 × (−0.20 ÷ 0.1) = −1.2 mEq/L. The corrected potassium is 5.8 − 1.2 = 4.60 mEq/L. Much of the high reading in this sample is therefore explained by the acidic pH rather than by a true excess of potassium.

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Common mistakes

  • Adding the correction when pH is low: the sign is built into the formula, so at pH 7.2 the value goes down, not up.
  • Entering the pH of a venous sample while treating it as arterial pH, or mixing values drawn at different times: potassium and pH must come from the same sample.
  • Using the result as a replacement for the measurement: the 0.6 factor is approximate, and the corrected figure is only a sanity check.
  • Typing the potassium in the wrong unit or with a misplaced decimal: the field expects mEq/L, such as 5.8, not 58 or 0.58.

Sources

About this calculator

Blood pH shifts change how potassium moves between blood plasma and body cells, so a measured serum potassium level can look artificially high or low if a patient's blood is more acidic or alkaline than the normal reference pH of 7.4. Corrected potassium adjusts the measured value back to what it would likely read at pH 7.4, using K_corrected = measured K + 0.6 × ((pH − 7.4) / 0.1) — for every 0.1 drop in pH below 7.4 (acidosis, which makes the measured value look too high), potassium is corrected downward by 0.6 mEq/L, and for every 0.1 rise above 7.4 (alkalosis) it is corrected upward by 0.6 mEq/L.

This correction is used in clinical chemistry and critical care, where a patient's arterial blood gas and electrolyte panel are often drawn together, so clinicians can tell whether an abnormal potassium reading reflects a true electrolyte imbalance or is simply an artifact of acidosis or alkalosis shifting potassium across cell membranes. It's a bedside sanity check rather than a replacement for clinical judgment, and any corrected value should always be interpreted alongside the patient's full clinical picture.

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Comments (1)

  • Editorial team

    The fixed 0.6 per 0.1 pH step is one straight-line rule, but the real potassium shift is generally described as depending on the kind of acidosis, and is usually thought to be smaller in organic acidoses such as lactic acidosis or ketoacidosis. So the farther the pH is from 7.4, the less you should lean on the corrected number. It is an educational estimate; the treating clinician decides what a value means. Which pH range do you most often adjust for?

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