Hormone Journal

Hyperkalemia

Pronounced: high-per-kuh-LEE-mee-uh

Also known as: high potassium

Medically reviewed by Hormone Journal Editorial Team · Last reviewed 2026-05-22

Hyperkalemia is a blood potassium level above 5.0 mmol/L that can cause life-threatening cardiac arrhythmias, most often triggered by kidney disease, aldosterone deficiency, or certain medications.

What it is

Hyperkalemia is defined as a blood potassium concentration above 5.0 mmol/L and is considered a medical emergency at levels above 6.5 mmol/L, where fatal cardiac arrhythmias become an immediate risk. Also called high potassium or hyperkalæmia, it affects an estimated 2–3% of the general population but rises to roughly 40–50% of patients with advanced chronic kidney disease (CKD). Potassium is an essential electrolyte that governs the electrical potential across cell membranes — the mechanism by which heart muscle, skeletal muscle, and nerves fire. The kidneys excrete roughly 90% of dietary potassium, a process tightly controlled by the adrenal hormone aldosterone. When that excretion fails — whether because the kidneys are damaged, aldosterone is deficient, or a medication blocks the system — potassium accumulates in the blood. For Canadian patients, serum potassium is a standard component of the comprehensive metabolic panel ordered through LifeLabs or Dynacare; results are reported in mmol/L, the unit used throughout Canadian clinical guidelines.

Causes and mechanism

The underlying problem in every case of hyperkalemia is an imbalance between potassium intake, cellular distribution, and renal excretion. The major categories are:

CategoryCommon examplesMechanism
HormonalAddison's disease, hypoaldosteronism, type 4 renal tubular acidosisAldosterone deficiency or resistance → kidneys cannot excrete K⁺
RenalChronic kidney disease, acute kidney injuryReduced nephron mass → impaired K⁺ filtration and secretion
MedicationsACE inhibitors, ARBs, potassium-sparing diuretics (spironolactone, amiloride), NSAIDs, calcineurin inhibitorsBlock renin-angiotensin-aldosterone system or directly impair tubular K⁺ secretion
Transcellular shiftMetabolic acidosis, insulin deficiency, rhabdomyolysis, tumour lysis syndromeIntracellular K⁺ moves into plasma
Excess intakeHigh-dose potassium supplements, salt substitutes, high-potassium diet in at-risk patientsOverwhelms excretory capacity
PseudohyperkalemiaHaemolysis during blood draw, prolonged sample transitArtifactual — confirmed by repeat testing

In the hormonal context, Addison's disease (primary adrenal insufficiency) is the most clinically significant cause: without aldosterone, the principal cells of the renal collecting duct cannot pump potassium into the tubular lumen for excretion, and levels rise steadily. Medications that suppress the renin-angiotensin-aldosterone system are the most common drug-related cause, particularly relevant in Canada where ACE inhibitors and ARBs are among the most widely prescribed antihypertensives.

Symptoms and diagnosis

Mild hyperkalemia (5.0–5.9 mmol/L) is usually asymptomatic and found incidentally on routine bloodwork. As levels climb, patients may notice muscle weakness or fatigue, cramps, tingling in the hands or feet, palpitations, or nausea. Severe hyperkalemia (above 6.5 mmol/L) can produce bradycardia, ventricular fibrillation, or cardiac arrest with little warning.

Diagnosis involves several steps:

  1. Serum potassium — the primary test; repeat if haemolysis is suspected.
  2. ECG — mandatory when potassium exceeds approximately 6.0 mmol/L; classic findings progress from tall peaked T waves to widened QRS to a sine-wave pattern.
  3. Renal function panel (creatinine, eGFR) — to assess kidney contribution.
  4. Aldosterone and plasma renin activity — to identify aldosterone deficiency or resistance.
  5. Cortisol and ACTH stimulation test — if Addison's disease is suspected.
  6. Medication review — to identify drug-related causes before attributing the finding to a primary disease.

Treatment options

Treatment is scaled to severity and directed at the underlying cause.

Acute / severe hyperkalemia (typically ≥ 6.0–6.5 mmol/L or symptomatic):

  • Calcium gluconate IV — stabilizes the cardiac membrane within minutes; does not lower potassium but buys time.
  • Insulin plus dextrose IV — drives potassium into cells, lowering serum levels by roughly 0.5–1.0 mmol/L within 30–60 minutes.
  • Salbutamol (nebulized) — beta-2 agonist that also shifts potassium intracellularly; used as an adjunct.
  • Sodium bicarbonate — corrects acidosis and aids transcellular shift in acidotic patients.
  • Potassium binders (patiromer, sodium zirconium cyclosilicate) — newer agents that bind potassium in the gastrointestinal tract and increase faecal excretion; both are available in Canada and listed on several provincial formularies.
  • Dialysis — reserved for severe refractory cases or patients with advanced kidney failure.

Hormonal cause (Addison's disease): Fludrocortisone replacement restores mineralocorticoid activity at the renal tubule, directly correcting the excretory defect. Potassium typically normalizes within days of adequate dosing.

Long-term management: Dietary potassium restriction (limiting bananas, oranges, avocados, potatoes, tomatoes, beans, and dairy), medication review and adjustment, and regular serum potassium monitoring in at-risk patients are the cornerstones of ongoing care.

When to see a clinician in Canada

Call 911 or go to the nearest emergency department immediately if you experience palpitations, an irregular heartbeat, sudden significant muscle weakness, or near-fainting — these can signal dangerous potassium levels requiring IV treatment.

See a physician or nurse practitioner promptly (within 24–48 hours) if a blood test has returned a potassium level above 5.5 mmol/L, even without symptoms. An ECG and repeat bloodwork are typically needed before a management plan can be confirmed.

If you have Addison's disease, diabetes, or CKD, or take ACE inhibitors, ARBs, or potassium-sparing diuretics such as spironolactone, you are at elevated baseline risk. Canadian patients in this group should discuss a monitoring schedule with their primary care provider; many provincial labs allow standing orders for periodic electrolyte panels through LifeLabs or Dynacare without a repeat clinic visit. Virtual care platforms — including Maple, Felix, Cleo, and others — can facilitate prescription reviews and requisition renewals between in-person appointments, though any potassium result above 6.0 mmol/L warrants in-person or emergency assessment.

Limitations and open questions

Research is still emerging on the optimal long-term use of newer potassium binders (patiromer and sodium zirconium cyclosilicate) in Canadian outpatient settings, and provincial formulary coverage varies. The precise potassium threshold at which to initiate dietary restriction versus pharmacological treatment in asymptomatic patients with mild hyperkalemia (5.0–5.5 mmol/L) is not firmly established, and practice varies across Canadian nephrology and endocrinology centres. Health Canada has not issued a standalone clinical guideline specific to hyperkalemia management; clinicians currently rely on international guidance from the Kidney Disease: Improving Global Outcomes (KDIGO) group and the Endocrine Society. The relationship between recurrent mild hyperkalemia and long-term cardiovascular outcomes in patients without CKD also remains incompletely characterized.

FAQs

What is the difference between hyperkalemia and hypokalemia?

Hyperkalemia means blood potassium is too high (above 5.0 mmol/L), while hypokalemia means it is too low (below 3.5 mmol/L). Both disrupt the electrical potential across muscle and heart cell membranes, but through opposite mechanisms. Hypokalemia is most often caused by diuretics, vomiting, or diarrhea, whereas hyperkalemia is most commonly driven by kidney disease, aldosterone deficiency, or medications that block the renin-angiotensin-aldosterone system. Both conditions require medical evaluation and, depending on severity, can be life-threatening.

Can Addison's disease cause dangerously high potassium?

Yes. In Addison's disease (primary adrenal insufficiency), the adrenal glands fail to produce adequate aldosterone, the hormone that signals the kidneys to excrete potassium. Without this signal, potassium accumulates in the blood. During an untreated adrenal crisis, potassium can rise to levels above 6.5 mmol/L, where the risk of ventricular fibrillation and cardiac arrest becomes real. Fludrocortisone — the synthetic mineralocorticoid used to replace aldosterone — is a non-negotiable part of Addison's disease treatment precisely because it corrects this excretory defect.

Which foods are highest in potassium and should I avoid them?

Foods with the highest potassium content include bananas, oranges, avocados, potatoes (especially the skin), tomatoes, beans and lentils, spinach, nuts, and dairy products. Whether you need to restrict these depends on your individual potassium level and kidney function — blanket avoidance is not recommended for people with normal kidneys. For patients with CKD, aldosterone deficiency, or other conditions that impair potassium excretion, a registered dietitian can set a personalized daily potassium target, typically in the range of 2,000–3,000 mg per day for those with moderate restriction needs.

Can high potassium cause muscle weakness?

Yes. Potassium maintains the resting electrical potential across muscle cell membranes; when blood levels are significantly elevated, that potential is disrupted and muscles cannot contract normally. Patients typically notice generalized weakness, fatigue, and sometimes cramping or tingling in the limbs. In severe cases, skeletal muscle paralysis can occur. The heart muscle is particularly sensitive: at potassium levels above roughly 6.5 mmol/L, the risk of life-threatening arrhythmias rises sharply, which is why an ECG is a standard part of the workup for significant hyperkalemia.

How is hyperkalemia from a hormonal problem different from hyperkalemia caused by kidney disease?

The distinction matters for treatment. In hormonal causes such as Addison's disease or isolated hypoaldosteronism, the kidney tissue itself is structurally intact but lacks the aldosterone signal needed to secrete potassium into the urine — replacing fludrocortisone corrects the problem directly. In CKD, the filtering capacity of the kidney is physically reduced, so potassium accumulates regardless of hormone levels; management focuses on dietary restriction, potassium binders, and sometimes dialysis. Blood tests showing low aldosterone with normal or elevated renin point toward a hormonal cause, while a reduced eGFR (typically below 30 mL/min/1.73 m²) points toward a renal cause — though both can coexist.

Sources

All glossary termsUpdated 2026-05-22