Hyperkalaemia: recognising and managing high potassium in general practice

Hyperkalaemia — a serum potassium above 5.0 mmol/L — is one of the most consequential electrolyte findings in Australian general practice. Most cases are discovered incidentally on routine blood tests in patients taking potassium-raising medications, particularly against a background of chronic kidney disease, heart failure, or diabetes. The clinical spectrum runs from a mild, manageable outpatient problem to a life-threatening cardiac emergency that requires immediate hospital transfer.

Understanding severity grading, identifying the cause, ruling out pseudohyperkalaemia, and choosing the right management pathway are the core GP skills this article addresses.

A. Core clinical — the AU general-practice framework

Severity classification

Therapeutic Guidelines (eTG) — Renal defines three severity tiers, each with a distinct management approach:

Grade	Serum potassium	Clinical implications
Mild	5.0–5.5 mmol/L	Typically asymptomatic; address cause and monitor
Moderate	5.6–6.0 mmol/L	Outpatient management with ECG; medication adjustment
Severe	≥6.1 mmol/L, or any level with ECG changes	Medical emergency — call ambulance

Critical rule: any potassium level — even 5.5 mmol/L — combined with ECG changes is a medical emergency regardless of the absolute number.

Pseudohyperkalaemia — exclude before treating

The most common cause of an apparently elevated potassium in general practice is a poor-quality sample. Haemolysis during venepuncture — from a tight tourniquet, prolonged stasis, a difficult draw, or delayed sample processing — releases intracellular potassium and produces a falsely elevated result. The laboratory usually flags haemolysed specimens, but not always.

Repeat with a careful venous sample — brief tourniquet, no fist clenching, same-day processing — before treating any asymptomatic patient with a plausible haemolysis history. Other causes of pseudohyperkalaemia include thrombocytosis above 1,000 × 10⁹/L and severe leukocytosis from chronic lymphocytic leukaemia or another haematological malignancy.

Symptoms — unreliable but important to ask

Mild and moderate hyperkalaemia is frequently asymptomatic. When symptoms do occur, they reflect impaired muscle and nerve membrane function: generalised weakness, fatigue, limb heaviness, perioral or extremity paraesthesia, and palpitations. At severe levels — usually above 6.5 mmol/L — cardiac conduction abnormalities can precipitate ventricular fibrillation or asystole, sometimes without any preceding warning.

Never use the absence of symptoms to reassure that potassium is safe; always obtain an ECG at or above 6.0 mmol/L or when any new symptom is reported.

Causes in Australian general practice

Drug-induced (most common). The term “triple whammy” — an Australian-coined description — refers to the high-risk combination of an ACE inhibitor or ARB, an NSAID, and a diuretic taken together. This combination reduces renal blood flow, blocks aldosterone simultaneously from multiple angles, and impairs potassium excretion. In practice, any stacking of potassium-raising agents against reduced kidney function is a risk. The key culprits:

• ACE inhibitors (ramipril, perindopril, lisinopril) — raise potassium approximately 0.5 mmol/L; the effect is amplified as kidney function declines.
• ARBs (irbesartan, telmisartan, candesartan, olmesartan) — similar effect to ACE inhibitors.
• Aldosterone antagonists (spironolactone, eplerenone) — raise potassium 0.5–1.0 mmol/L; additive with ACE inhibitors or ARBs.
• Potassium-sparing diuretics (amiloride, triamterene).
• NSAIDs (ibuprofen, naproxen, diclofenac, celecoxib) — reduce renal blood flow via afferent arteriolar vasoconstriction.
• Trimethoprim (co-trimoxazole / Bactrim) — competes with aldosterone at the renal tubular level; a frequently overlooked cause in older patients with CKD on short-course antibiotics.
• Salt substitutes (LoSalt, “lite salt”) — contain potassium chloride; patients are often unaware these are pharmacologically equivalent to supplemental potassium.

Chronic kidney disease. As eGFR falls below 30 mL/min/1.73m², potassium excretion capacity declines significantly. CKD stage 4–5 combined with RAAS blockade is the highest-risk combination routinely encountered in general practice.

Mineralocorticoid deficiency. Primary adrenal insufficiency (Addison’s disease) presents with hyponatraemia, hyperkalaemia, and hypotension. This triad should always prompt a 9 AM cortisol and short Synacthen test.

Cellular potassium release. Rhabdomyolysis, tumour lysis syndrome, severe metabolic acidosis (including diabetic ketoacidosis), and massive blood transfusion all shift intracellular potassium into the circulation acutely.

Assessment

A thorough medication review is the single most important step. Establish the complete list — including over-the-counter NSAIDs, herbal products, and potassium-containing salt substitutes. Assess kidney function history, recent illness, dietary habits, and symptoms (weakness, palpitations, paraesthesia).

Examination: vital signs, volume status, neuromuscular strength, reflexes, and skin pigmentation (Addison’s).

Investigations: obtain an ECG for any potassium ≥6.0 mmol/L or symptoms. ECG changes in hyperkalaemia progress predictably: peaked or tented T waves appear first (typically at 5.5–6.5 mmol/L), followed by prolonged PR interval and flattened P waves (6.5–7.5), widened QRS (7.5–8.0), then sine-wave pattern and ventricular fibrillation or asystole. Blood tests: U&E, eGFR, glucose, magnesium, calcium, phosphate, FBC, and CK if rhabdomyolysis is possible.

B. Managing by severity

Mild hyperkalaemia (5.0–5.5 mmol/L, asymptomatic, no ECG changes)

Per eTG Renal and AMH, management is outpatient:

1. Confirm the result is not pseudohyperkalaemia.
2. Medication review — identify the offending drug; consider dose reduction or cessation under GP supervision. Communicate with the prescribing cardiologist or nephrologist before stopping heart-failure or CKD medications.
3. Dietary advice — reduce high-potassium foods (bananas, potatoes, tomatoes, dried fruit, mushrooms, spinach) and ask specifically about potassium-containing salt substitutes.
4. Recheck electrolytes in 1–7 days depending on clinical context and the degree of elevation.

Moderate hyperkalaemia (5.6–6.0 mmol/L, asymptomatic, no ECG changes)

Outpatient management is appropriate when the patient is asymptomatic, the ECG is normal, and close follow-up is reliably achievable:

1. All steps for mild hyperkalaemia.
2. Cease or reduce the offending potassium-raising agent if clinically safe — discuss dose reduction of ACE inhibitor or ARB rather than abrupt cessation when prescribed for heart failure or proteinuric CKD.
3. Oral potassium binders if dietary and medication adjustments are insufficient:
   • Sodium polystyrene sulfonate (Resonium A) — PBS general schedule, no authority required; 15–30 g two to four times daily; historically the first-line option; GI side effects (constipation, nausea) are common; rare colonic necrosis if given to bowel-obstructed patients.
   • Patiromer (Veltassa) — Authority Required (Written) for chronic hyperkalaemia in patients on RAAS therapy where RAAS continuation is clinically necessary; 8.4–25.2 g daily; better GI tolerability; preferred for long-term management.
   • Sodium zirconium cyclosilicate (Lokelma) — Authority Required for the same indication; rapid onset (within one hour); 5–10 g one to three times daily.
4. Recheck electrolytes within 48 hours.

Severe hyperkalaemia (≥6.1 mmol/L, or any ECG changes, or symptomatic)

This is a medical emergency. Call an ambulance and arrange immediate hospital transfer. While awaiting transfer, begin in-clinic stabilisation per AMH emergency guidance:

1. IV calcium gluconate 10 mL of 10% solution over 2–3 minutes — stabilises the cardiac cell membrane; does not lower serum potassium; onset within minutes; lasts 30–60 minutes; repeat at 5–10 minutes if ECG changes persist.
2. IV short-acting insulin 10 units + 50 mL 50% glucose — drives potassium into cells via the sodium-potassium-ATPase pump; onset 15–30 minutes; lasts 4–6 hours; monitor blood glucose hourly; give glucose first in non-diabetic patients to prevent hypoglycaemia.
3. Salbutamol nebuliser 10–20 mg — β2-adrenergic receptor stimulation drives intracellular potassium shift; additive effect with insulin; use with caution in tachyarrhythmia or ischaemic heart disease.
4. Sodium bicarbonate 50–100 mmol IV if metabolic acidosis with pH below 7.2.
5. Continuous ECG monitoring until serum potassium normalises.

C. The RAAS dilemma — chronic management

The most clinically important long-term question is whether to continue ACE inhibitor or ARB therapy in a CKD or heart failure patient who develops persistent hyperkalaemia. Stopping RAAS therapy removes a medication with substantial mortality benefit — approximately 25% reduction in cardiovascular events in heart failure with reduced ejection fraction, and meaningful renoprotection in proteinuric CKD, per KDIGO 2024 guidelines.

The current evidence-informed approach:

• Where RAAS continuation is clinically critical (heart failure with reduced ejection fraction, proteinuric diabetic kidney disease): continue RAAS at the lowest effective dose and add a potassium binder to enable chronic management. This is supported by the PEARL-HF trial (Bakris NEJM 2015), which demonstrated patiromer allowed continuation of spironolactone in heart failure patients who had previously been intolerant, and by the HARMONIZE study (Spinowitz CJASN 2019) for sodium zirconium cyclosilicate.
• Where RAAS is prescribed primarily for blood pressure and an alternative agent is available: consider switching to a calcium channel blocker or thiazide-type diuretic.
• Sick-day rules for all CKD + RAAS patients: pause ACE inhibitor or ARB, potassium-sparing diuretic, and NSAIDs during diarrhoea, vomiting, or fever lasting more than 24 hours, then restart when well.

D. Australian operations

MBS items

Standard general practice consultation items apply: 23, 36, and 44. When hyperkalaemia occurs in the context of CKD or diabetes managed under a GP Management Plan and Team Care Arrangement, items 965 and 967 apply. In-clinic ECG: item 11700.

PBS

• Resonium A (sodium polystyrene sulfonate) — general schedule; no authority required.
• Veltassa (patiromer) — Section 85 Authority Required (Written); indication is chronic hyperkalaemia in patients on RAAS inhibitor therapy with CKD or heart failure with reduced ejection fraction, where RAAS continuation is clinically necessary.
• Lokelma (sodium zirconium cyclosilicate) — Authority Required for the same indication as patiromer.

Referral pathways

• Emergency department (same day or ambulance): K+ ≥6.5 mmol/L; K+ ≥6.0 mmol/L with ECG changes; symptomatic at any level.
• Nephrology (within one week): recurrent moderate hyperkalaemia despite medication optimisation; CKD stage 4–5 requiring chronic potassium binder; suspected type 4 renal tubular acidosis (mild metabolic acidosis + hyperkalaemia + normal anion gap in diabetic nephropathy).
• Endocrinology: suspected primary adrenal insufficiency or isolated hypoaldosteronism.

Medico-legal notes

The clinical record should capture: the potassium result, whether pseudohyperkalaemia was considered, the ECG findings, the management plan, and the arranged follow-up interval. Failure to recognise severe hyperkalaemia and arrange timely emergency transfer carries medico-legal risk. The triple-whammy combination (ACE inhibitor or ARB + NSAID + potassium-sparing diuretic) should be documented as contraindicated in the patient’s record, with specific patient counselling about avoiding over-the-counter ibuprofen and naproxen.

E. Special populations

Older adults are at substantially higher risk because of frequent polypharmacy combining multiple potassium-raising agents — antihypertensives, heart failure medications, anti-inflammatory analgesics — combined with reduced renal reserve from ageing and lower muscle mass. Medication review at every chronic-disease consultation is essential. Trimethoprim-based antibiotic prescriptions in older patients with CKD warrant a potassium check 5–7 days after initiation.

Chronic kidney disease. As eGFR falls below 30 mL/min/1.73m², even small changes in dietary intake or medication can push potassium into moderate or severe territory. Quarterly to six-monthly electrolyte monitoring is standard for CKD stage 4–5 on RAAS therapy. Shared care with nephrology is appropriate when binder therapy is initiated or RAAS management becomes complex.

Diabetes. Type 4 renal tubular acidosis — characterised by mild metabolic acidosis, hyperkalaemia, and normal anion gap — is particularly common in diabetic nephropathy from hyporeninaemic hypoaldosteronism. These patients may develop moderate hyperkalaemia on modest RAAS doses with only mildly reduced eGFR.

Heart failure. The combination of ACE inhibitor, spironolactone, and reduced eGFR from poor cardiac output is a high-risk triad in general practice. Monthly electrolyte monitoring for three months, then quarterly, is appropriate after any dose change in this group. Consider nephrology or cardiology shared care.

Pregnancy. ACE inhibitors and ARBs are absolutely contraindicated in pregnancy because of foetal renal toxicity (oligohydramnios, renal tubular dysgenesis, limb contractures, death). A woman found to be pregnant while on these agents requires immediate cessation and urgent obstetric review.

When to escalate

• Potassium ≥6.5 mmol/L — emergency department immediately, call ambulance.
• Any potassium level with ECG changes — emergency department immediately.
• Symptomatic hyperkalaemia (palpitations, chest pain, syncope, severe weakness) — triple zero (000).
• Suspected adrenal insufficiency (hyperkalaemia + hyponatraemia + hypotension + skin pigmentation) — urgent same-day assessment; do not delay empirical hydrocortisone if the diagnosis is suspected clinically.
• Suspected rhabdomyolysis (markedly elevated CK, dark brown urine, muscle pain post-trauma or strenuous exercise) — emergency department.
• Recurrent moderate hyperkalaemia despite full medication optimisation — nephrology referral within one week.

What this article is and is not

This is general health information based on current Australian clinical guidelines — Therapeutic Guidelines (eTG), Australian Medicines Handbook (AMH), RACGP, and KDIGO 2024 — written for patients who want to understand what a raised potassium result means and how a general practitioner approaches it. It is not personal medical advice and does not substitute for review by your own GP or specialist. Decisions about medication changes — including adjusting or stopping ACE inhibitors, ARBs, or spironolactone — should always be made in consultation with your treating clinician.

If you are experiencing palpitations, chest pain, severe weakness, or feel faint, call triple zero (000) immediately.

For Australian health information: HealthDirect, Better Health Channel.

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Sources cited

1. Therapeutic Guidelines (eTG) — Renal and Electrolytes
2. Australian Medicines Handbook (AMH)
3. RACGP — Hyperkalaemia management in general practice
4. PBS — Resonium A, Veltassa, and Lokelma listings
5. MBS Online — ECG item 11700
6. MBS Online — GPCCMP item 965
7. KDIGO 2024 — Chronic kidney disease clinical practice guideline
8. BMJ Best Practice — Hyperkalaemia
9. HealthDirect — Potassium and electrolytes
10. Better Health Channel — Blood tests: electrolytes
11. Bakris GL et al. — Patiromer for hyperkalaemia in CKD — PEARL-HF (NEJM 2015)
12. Spinowitz BS et al. — Sodium zirconium cyclosilicate in hyperkalaemia (CJASN 2019)