Algorithm of the cause of Hypokalaemia

A history of vomiting, diarrhoea, or use of medications such as diuretics can be helpful in determining the cause of hypokalaemia. However, in some cases, the cause of hypokalaemia is not readily apparent. In these cases, measurements of BP and urinary potassium excretion, and assessment of acid-base balance are often helpful.

Serum potassium concentrations:
There is no strict correlation between the serum potassium concentration and total body potassium stores. In chronic hypokalaemia, a potassium deficit of 200 to 400 mmol (200 to 400 mEq) is required to lower the serum potassium concentration by 1 mmol/L (1 mEq/L). These estimates are good provided there is no concurrent acid-base abnormality (e.g., for diabetic ketoacidosis or severe non-ketotic hyperglycaemia).

In diabetic ketoacidosis patients may have a normal or even elevated serum potassium concentration at presentation, despite having a marked potassium deficit due to urinary and GI losses.

Spurious hypokalaemia can occur when blood with a high WBC count is left at room temperature due to extraction of potassium by the WBCs. It is therefore important to consider repeating the test for confirmation.