Potassium (Hypo-hyperkalaemia)

What is Hypokalaemia?

Hypokalaemia means potassium < 3.5 mmol/L.

It can cause muscle weakness and heart rhythm problems. Severe hypokalaemia (< 2.5 mmol/L) is life-threatening.

Severity Guide

  • Mild: 3.0-3.4 mmol/L
  • Moderate: 2.5-2.9 mmol/L
  • Severe: < 2.5 mmol/L or ECG changes

Primary Care Management

  • Step 1: Review and context
    • Check symptoms: weakness, cramps, palpitations
    • Review previous potassium levels
  • Step 2: Check for common causes
    • Diuretics (e.g. furosemide, bendroflumethiazide)
    • Vomiting or diarrhoea
    • Poor intake
    • Recent insulin use or beta-agonists
  • If Mild (3.0-3.4 mmol/L) and well
    • Try oral potassium replacement (e.g. Sando-K 1-2 tablets TDS for 3-5days to begin with)
    • Repeat U&Es + magnesium in 3-7 days (if possible)
    • Stop Sando K once potassium ≥3.5 mmol/L and cause addressed
  • If Moderate (2.5-2.9 mmol/L)
    • Check magnesium urgently and correct if low
    • If asymptomatic and no cardiac disease → try sando-k 2 tablets QDS (≈96 mmol/day) for 3-5 days
    • Repeat u&es within 2-3 days
    • If heart disease, symptoms, ECG changes or unable to tolerate oral → same-day hospital referral
  • Severe (< 2.5 mmol/L) or palpitations/chest symptoms
    • Same-day hospital referral
    • Do not delay waiting for oral replacement

Secondary Care Management

  • Continuous ECG monitoring if K+ < 3.0 mmol/L
  • Check magnesium and replace if low
  • IV potassium chloride if unable to take orally or severe
  • Typical IV rate: 20-40 mmol in 1L sodium chloride over 4-6 hours (ensure you follow local protocol)
  • Recheck potassium every 4-6 hours in severe cases

Common Causes

  • Medications: diuretics, steroids, beta-agonists
  • GI losses: vomiting, diarrhoea
  • Low magnesium: prevents potassium correction
  • Renal losses: hyperaldosteronism, tubular disorders
  • Shift into cells: insulin, alkalosis, refeeding

Prevention and Follow-Up

  • Correct underlying cause
  • Review need for diuretics
  • Encourage dietary potassium if appropriate
  • Recheck U&Es after treatment until stable

What is Hyperkalaemia?

Hyperkalaemia means potassium is raised. Clinically significant hyperkalaemia is usually ≥ 5.5 mmol/L.

Risk of dangerous heart rhythm problems increases as potassium rises.

Severity Guide

  • Mild: 5.5-5.9 mmol/L
  • Moderate: 6.0-6.4 mmol/L
  • Severe: ≥ 6.5 mmol/L or ECG changes

Primary Care Management

Mild Hyperkalaemia (5.5-5.9 mmol/L) and Patient Well
  • Check for haemolysis on lab report (spurious result common)
  • Review previous potassium levels (trend important)
  • Stop or review potassium-raising medicines where safe:
    • ACE inhibitors / ARBs
    • Spironolactone / eplerenone
    • Potassium supplements
    • NSAIDs
    • Trimethoprim
  • Assess for dehydration and encourage fluids if appropriate
  • Arrange repeat U&Es in 1-2 weeks
  • Escalate earlier if CKD stage 4-5, AKI suspected, or rising trend

Potassium ≥ 6.0 mmol/L

  • Urgent GP/clinician review required
  • With a view to referral to A&E
  • Do not delay waiting for routine repeat blood tests
  • If symptomatic (chest pain, palpitations, weakness, collapse) → call 999
  • Higher risk if CKD stage 4-5, suspected AKI, or rising potassium trend

Secondary Care Management (Overview)

Initial Assessment
  • Immediate ECG
  • Repeat potassium urgently
  • Continuous cardiac monitoring if ≥ 6.0 mmol/L
If ECG changes or potassium ≥ 6.5 mmol/L
  • IV calcium gluconate to stabilise myocardium
Shift potassium into cells
  • Insulin + glucose infusion (per local protocol)
  • Nebulised salbutamol
Remove potassium from body
  • Treat underlying cause
  • Loop diuretics if appropriate
  • Potassium binders as per local guidance
  • Dialysis if refractory or severe renal failure

Common Causes

  • Reduced excretion: AKI, CKD
  • Medications: ACE inhibitors, ARBs, spironolactone, NSAIDs, trimethoprim
  • Metabolic acidosis
  • Tissue breakdown: rhabdomyolysis
  • Spurious result: haemolysed sample

Follow-Up in Primary Care

  • Repeat U&Es 1-2 weeks after medication changes
  • Review long-term need for RAAS inhibitors
  • Consider renal referral if recurrent or CKD progressing
  • Document trigger and escalation plan clearly
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