Potassium - Hypokalaemia

Hypokalaemia is defined as a serum potassium of

Hypokalaemia generally means hypomagnesaemia, measure and replace Mg2+ as required.



  • Usually asymptomatic, but…

  • Weakness, lethargy, paralysis, tetany

  • Cardiac dysrhythmias if severe:

    • VT, VF, heart block, asystole


Bloods EUC ideally via Venous Blood Gas.

ECG done early on suspicion of electrolyte abnormalities:

  • Normal, flattened T waves, peaked P waves

  • U wave.


Cardiac monitoring and treatment of cause are the underlying principles. The rate of replacement and methods are highly dependent on the symptoms and signs and degree of deficit.

If mild

  • Oral K replacement - 40mmol in 4-6 hours with K+ tablets, SlowK and SpanK ( swallowede whole and 8mmol per tablet) Chlorvescent (dissolved, 14 mmol/L)

  • Slow K not as effective as effervescent immediate release and less K+

  • Oral is usually best but can lead to GI upset

Replacement of magnesium - 10mmols over 20 minutes which is invariably low in hypokalaemia.

If moderate to severe K 2.5- 3.0mmol/L and asymptomatic

  • Replace as per mild if can take oral

  • Consider IV replacement as for severe

If moderate to severe K

  • IVI Potassium Chloride ideally use preloaded infusions e.g. 30mmol/L in 1000 mLs, or 10mmol/100 mLs, usually at rates of 10-20mmols per hour

  • Via central or large peripheral IV line, greater than 10 mmol/hr can cause discomfort and vein damage in peripheral lines

  • Maximum 40mmol per hour

  • Cardiac monitoring whilst infusing

  • Concurrent oral can be used if conscious

Note: 20mmol K will raise serum K by 0.5-0.75mmol l-1, this can vary and is only a guide depending on the cause ongoing losses and state of hydration.

If severe K

  • 10mmol as a push dose

What's New

© Agency for Clinical Innovation 2021