Lab case 374 Interpretation

This patient’s blood test showed high K level with low Mg and Ca levels.

Deranged electrolytes levels usually happen due to one of five reasons:

  • Intake (Increased or reduced)
  • Excretion (Increased or reduced)
  • Tissue destruction leading to released electrolytes to the circulation
  • Redistribution between intracellular and extracellular compartments
  • Fictitious or laboratory error.

Hypomagnasaemia is usually associated with hypokalaemia and hypercalcemia.

The only time hypomagnasaemia can occur with hyperkalaemia is in cases of stage 4 renal failure. Clearly this patient doesn’t have that as the kidney function is within normal range.

Major burns can cause hypomagnesemia by provoking inappropriate renal magnesium wasting. Patients with extensive burns often present with hypocalcemia due to abnormalities in bone metabolism and an inability to produce normal vitamin D levels in the skin. This patient presented with vertigo.

Some medications can cause multiple electrolytes abnormalities.

For examples:

  • Loop diuretics can cause hypocalcemia and hypomagnasaemia. However, they also cause hypokalaemia (Not hyperkalaemia).
  • PPI can lead to serious hypomagnasaemia. current evidence suggests that it is caused by impaired intestinal absorption of Mg. There are reported cases of hypocalcaemia and hyperkalaemia associated with PPI use. Hypocalcaemia is caused by reduced Calcium absorption secondary to acid suppression as the acidic environment in the stomach increases calcium solubility by releasing ionized calcium salts from its insoluble forms. PPI may suppress adrenal cortical steroid synthesis and release, thereby can cause to hyponatremia and hyperkalemia – This patient was not taking PPIs.

Laboratory or collection error is always a potential cause, always repeat the test if the results unexplainable.

Repeat blood tests for this patient was normal.

In this case the person collected the blood put the blood in a purple-top tube first (EDTA), then aspirated some of this blood and put it in the yellow-top tube leading to EDTA contamination and deranged electrolytes results.

  • EDTA inhibits clotting by chelation of the divalent cations Ca and Mg, which inhibits several of cation-dependent proteolytic enzymes critical to the clotting cascade. EDTA is a K containing salt, that is why contamination by EDTA leads to invalid interpretation of potassium status.


Many thanks to Dr Elissa Poulter for providing the details of this case