Calcium resonium

Also called calcium polystyrene sulfonate

Calcium resonium is a medicine that is used to treat high potassium levels. Find out how to take it safely and the possible side effects. Calcium resonium is also called calcium polystyrene sulfonate.

What is calcium resonium?

Calcium resonium is used to treat high potassium levels (hyperkalaemia). This is when there is too much potassium in your blood. Calcium resonium works by binding itself to potassium in your digestive tract, mainly the large intestine. This helps prevent your body from absorbing too much potassium. People with severe kidney disease often have high potassium levels as their kidneys can't remove potassium from the body.


In Aotearoa New Zealand, calcium resonium is available as a powder. 

  • The dose of calcium resonium will be different for different people. It depends on your potassium levels, how often you have dialysis and your response to treatment.
  • Adults: The usual dose for adults is 15 grams 3 to 4 times daily, but some people may need less frequent doses, eg, once daily or only on certain days of the week.
  • Children: The dose depends on how much the child weighs.
  • How long you need to take calcium resonium will depend on 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 recently, 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, check with your doctor or pharmacist. 

How to take calcium resonium

Measuring your dose

Use the spoon provided in the jar of powder to measure your dose. The spoon contains 15 grams of powder when filled and levelled. You can use ONE level tablespoon if no scoop is provided in the container.

Mixing the powder

To take the powder, mix it with a little water. If you don't have diabetes, you can mix it with something sweet, such as jam or honey, to make it taste better. DO NOT MIX WITH FRUIT JUICE OR MILK BASED PRODUCTS as these are high in potassium. Once the mixture has been prepared it should be used straight away. If it needs to be stored, it should be stored for no longer than 24 hours. If you have been prescribed lactulose liquid while you are taking calcium resonium, you can mix the lactulose with the calcium resonium (see below).

Taking calcium resonium with lactulose

You may be prescribed lactulose liquid while you are taking calcium resonium.

  • Lactulose liquid helps you pass bowel motions to get rid of potassium from the body once it is bound to resonium.
  • It also helps prevent constipation which is a common side effect of calcium resonium.
  • You will need to keep your bowels working so the potassium can leave your body. Aiming for 1 to 2 soft motions per day is ideal.
  • If you have been advised to restrict your fluid intake, you can mix the lactulose with the calcium resonium. They may not fully mix, and that’s ok.

Taking other medicines

Take calcium resonium at least 3 hours before or 3 hours after other medicines. Discuss with your doctor or pharmacist how best to time your medicines while you are taking calcium resonium. Taking other medicines at the same time as calcium resonium may prevent your body from absorbing the medicine, and it may not work as well as it should. 

Tell your doctor or pharmacist about all the medicines you are taking. This includes over-the-counter medicines, herbal and complementary medicines, Rongoā Māori and recreational drugs. Your doctor or pharmacist will be able to check for any interactions between them.

Avoid products containing sorbitol

Sorbitol is a fruit sugar that is often used as a sweetener in many foods. Avoid eating or drinking anything that contains sorbitol such as chewing gum, diet drinks, baked goods, or frozen desserts. This can increase your risk of side effects.

Missed doses

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 2 doses at one time or close together.

Possible side effects 

Like all medicines, calcium resonium can cause side effects, although not everyone gets them. 

Side effects What should I do?
  • Constipation (unable to poo)
  • Tell your doctor immediately.
  • Nausea (feeling sick)
  • Indigestion
  • Diarrhoea (runny poos)
  • Tummy upset
  • Tell your doctor if these are bothering you.
  • Muscle cramps
  • Loss of appetite
  • Tell your doctor if these are bothering you.
  • Signs of high potassium levels such as muscle weakness, general weakness or tiredness, nausea, muscle pain or cramps, difficulty breathing, unusual heartbeat, chest pains 
  • Tell your doctor immediately or ring Healthline 0800 611 116.
  • Signs of an allergic reaction such as a rash or swelling of the face, lips, mouth or throat
  • Hives or itchy skin
  • Tell your doctor immediately or ring Healthline 0800 611 116.
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

The following link has more information on calcium resonium.
Calcium resonium Medsafe Consumer Information, NZ


  1. Calcium resonium NZ Formulary, NZ
Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, Pharmacist, Auckland Last reviewed: 09 May 2022