Potassium is an electrolyte essential for maintaining electrical gradients across cell membranes, enabling nerve impulses, muscle contractions, and heart rhythm. The normal serum potassium range is 3.5 to 5.0 mmol/L. Even small deviations outside this range can significantly affect cardiac and neuromuscular function.

There are two distinct potassium disorders:

Hypokalaemia is a serum potassium below 3.5 mmol/L. It is the more common of the two. Mild hypokalaemia causes subtle symptoms. Severe hypokalaemia below 2.5 mmol/L can cause dangerous cardiac arrhythmias and muscle paralysis.

Hyperkalaemia is a serum potassium above 5.0 mmol/L. It is particularly dangerous in people with kidney disease or those taking certain medications. Severe hyperkalaemia above 6.5 mmol/L is a cardiac emergency, capable of causing life-threatening arrhythmias and cardiac arrest.

Both hypokalaemia and hyperkalaemia affect the heart and muscles most prominently. Symptoms vary by severity.

Hypokalaemia symptoms:

• Muscle weakness, cramps, and fatigue

• Constipation and abdominal bloating

• Heart palpitations or irregular heartbeat

• Tingling or numbness

• In severe cases: muscle paralysis and life-threatening cardiac arrhythmias

Hyperkalaemia symptoms:

• Muscle weakness or heaviness, particularly in the legs

• Fatigue and general malaise

• Tingling or numbness

• Heart palpitations or irregular heartbeat

• In severe cases: cardiac arrest without warning

Mild potassium abnormalities frequently cause no symptoms at all, making routine blood testing the only reliable detection method.

The causes of hypokalaemia and hyperkalaemia are distinct.

Hypokalaemia causes:

• Diuretic medications are the most common cause. Thiazide and loop diuretics increase renal potassium excretion significantly.

• Vomiting and diarrhoea cause direct gastrointestinal potassium loss alongside dehydration.

• Magnesium deficiency impairs renal potassium reabsorption. Hypokalaemia that does not respond to potassium supplementation should always prompt magnesium assessment.

• Primary hyperaldosteronism causes excess aldosterone production that drives renal potassium wasting alongside hypertension.

• Inadequate dietary intake particularly in older adults or those with restrictive diets.

• Laxative overuse causes potassium loss through the gastrointestinal tract.

• Insulin excess drives potassium into cells, temporarily lowering serum levels.

Hyperkalaemia causes:

• Chronic kidney disease is the most common cause. The kidneys are the primary route of potassium excretion and impaired function allows it to accumulate.

• ACE inhibitors, ARBs, and potassium-sparing diuretics reduce renal potassium excretion, raising levels particularly in those with underlying kidney disease.

• Adrenal insufficiency reduces aldosterone, impairing renal potassium excretion.

• Diabetes with poor blood sugar control causes hyperkalaemia through insulin deficiency and metabolic acidosis.

• Significant tissue damage from burns, rhabdomyolysis, or major surgery releases intracellular potassium into the bloodstream.

• Excessive potassium supplementation particularly in those with impaired kidney function.

Potassium disorders are detected directly through blood testing, with supporting markers identifying the underlying cause and assessing the clinical impact.

Blood tests Elfcare's panel includes potassium alongside key related markers:

• Serum potassium: the primary measurement used to identify levels that are too high or too low.

• Sodium and bicarbonate: provides context on your body's acid-base balance, which dictates how potassium moves in and out of your cells.

• Creatinine and eGFR: evaluates kidney health, as the kidneys are responsible for clearing excess potassium from the body.

• Magnesium: essential for potassium regulation; low potassium often won't improve until magnesium levels are fixed.

• Glucose and HbA1c: checks for diabetes or insulin issues, which can cause potassium to build up to dangerous levels.

• Aldosterone and renin: identifies hormonal imbalances that can cause the body to lose too much potassium while raising blood pressure.

• Cortisol: screens for adrenal issues that may cause the body to retain too much potassium.

• CRP: a marker of inflammation and tissue damage, which can release excess potassium into the bloodstream.

• Full blood count: assesses whether haemolysis, a common cause of falsely elevated potassium in blood samples, may be contributing to apparent hyperkalaemia.

Why early detection matters

Mild potassium abnormalities cause few or no symptoms yet create the conditions for sudden and potentially fatal cardiac arrhythmias. The heart is exquisitely sensitive to potassium imbalance, and the transition from asymptomatic mild abnormality to life-threatening arrhythmia can occur rapidly, particularly in people with underlying heart disease or kidney impairment. Identifying potassium disorders through routine blood testing, before symptoms develop, allows for correction of the underlying cause and prevention of the serious cardiac consequences that undetected and untreated potassium imbalance can cause.

How Elfcare can help

Elfcare's blood panel measures serum potassium as standard alongside sodium, magnesium, creatinine, eGFR, glucose, HbA1c, and CRP. This provides both the direct potassium measurement and the metabolic, renal, and electrolyte context needed to identify the underlying cause and assess clinical risk.

Measuring magnesium alongside potassium is particularly important and is frequently overlooked in standard testing. Persistent hypokalaemia almost always indicates magnesium deficiency when it fails to respond to potassium supplementation alone.

If our blood tests identify a potassium disorder or related electrolyte imbalance, we take care of further diagnostics or refer you to the appropriate specialist.