Potassium chloride

Potassium chloride is a potassium supplement used to increase the amount of potassium in your body. Find out how to take it safely and possible side effects. Potassium chloride is also called Span-K or Chlorvescent.

Type of medicine Also called
  • Potassium supplement
  • Increases the amount of potassium in your blood
  • Span-K®
  • Chlorvescent®
  • Potassium chloride

What are potassium supplements?

Potassium supplement are used to increase the amount of potassium in your body. Having the right amount of potassium in your body is important for the working of your heart, kidneys, liver, muscles and nerves. 

Most people get enough potassium by eating a balanced diet. However, some conditions may lower your potassium levels, such as ongoing diarrhoea and vomiting, hormone problems (such as hyperaldosteronism) and medications such as diuretics (water pills), or corticosteroids.  

In New Zealand, potassium supplements are available as tablets or can be given as an injection in the hospital. 


  • The dose of potassium tablets will be different for different people. It will depend upon the level of potassium in your blood. Your doctor will check your potassium levels to make sure you are taking the right dose, especially if your other medicines have changed, or if you have been unwell.
  • Always take your medicine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions. If you are not sure of the right dose to take, or if your dose changes check you are taking the right amount with your doctor or pharmacist. 

How to take potassium supplements

  • You may be given potassium supplements as tablets (Span K) or as effervescent tablets (Chlorvescent).
  • They best taken with or after food, to prevent stomach upset.  
  • Tablets (Span K): swallow your tablets whole with a glass of water. Do not crush or chew them.
  • Effervescent tablets (Chlorvescent): dissolve each tablet in half a glass of cold water before swallowing. Make sure the tablets are completely dissolved before drinking the solution. 
  • If you forget to take your dose, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Precautions before starting potassium supplements

  • Do you have problems with your kidneys, liver or heart?
  • Do you have stomach ulcers?
  • Are you pregnant or breastfeeding?
  • Are you taking any other medicines? This includes any medicines you are taking that you can buy without a prescription, as well as herbal and complementary medicines. Some vitamins, mineral supplements and salt substitutes may contain potassium.

If so, it’s important that you tell your doctor or pharmacist before you start potassium supplements. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of potassium chloride?

Like all medicines, potassium supplements can cause side effects, although not everyone gets them. 

Side effects What should I do?
  • Feeling sick or vomiting
  • Take potassium after meals
  • Make sure the effervescent tablets are dissolved completely in water before taking them
  • Tell your doctor if troublesome
  • Loose stool or diarrhoea
  • Bloating or gas in the stomach  
  • Tell your doctor if troublesome
  • Muscle weakness
  • Changes in your heartbeat
  • Tell your doctor immediately
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product

Learn more

Potassium supplements New Zealand Formulary
Potassium salts Patient Info, UK.  


  1. Potassium salts (oral) New Zealand Formulary

Additional resources for healthcare professionals

Potassium chloride NZ Formulary
Span-K Medsafe, NZ
A primary care approach to sodium and potassium imbalance BPAC, NZ, 2011

Credits: Sandra Ponen, pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 29 May 2019