Potassium

Potassium is a naturally occurring mineral that is found in many foods and drinks. Your body needs potassium for almost everything it does, including making sure your nerves, muscles and heart work properly.

On this page, you can find the following information:

What is potassium important for?

Potassium is a mineral that is important for the working of your heart, kidneys, liver, muscles and nerves. Getting enough potassium can also help lower your risk of heart disease and stroke. The amount of potassium you need depends on your age, sex and any medical conditions you may have. You should be able to get all the potassium you need by eating a varied and balanced diet. 

Our kidneys help to control the level of potassium in the blood. Potassium not needed by the body is usually passed out in the urine. Low or high potassium is more common in older people and those with other conditions such as kidney problems or heart failure.

Too much potassium
People with kidney problems often have high potassium levels as the kidney is unable to remove potassium from the body. Some medicines can cause your body to hold on to potassium, eg, ACE inhibitors, spironolactone or angiotensin receptor blockers. Too much potassium can cause stomach pain, feeling sick and diarrhoea (runny poo). A high level of potassium can be dangerous, as it can affect your muscles and heart.

Too little potassium
Some conditions may lower your potassium levels, such as ongoing diarrhoea and vomiting, inflammatory bowel disease and medications such as diuretics (water pills), corticosteroids or excessive use of laxatives. Too little potassium can make you feel tired or nauseous (sick). If your potassium levels are low for a long time, this can cause high blood pressure, breathing problems or can cause your heart to beat irregularly. 

How do you test potassium levels?

Your doctor may check your potassium levels by a blood test. If you have too much or too little potassium in your body, your doctor may advise you to change your diet. Your doctor may prescribe a potassium supplement if you cannot get enough potassium from your diet.

It can be harder to have a well-balanced diet when you are changing your diet. You may also find it difficult to follow the advice on this page if you are already following a special diet for another reason. Your doctor may be able to refer you to a dietician if you need extra help.

What foods contain low or high potassium?

  Foods and drinks containing higher levels of potassium Foods and drinks containing lower levels of potassium
Fruits
  • Avocado, banana, orange
  • Dried fruits, eg, raisins, sultanas, prunes
  • All types of nuts, eg, almonds, peanuts.
  • Apple, peach, nectarine, pear
  • Clementine, mandarin, satsuma
  • Kiwifruit
  • Grapes
  • All canned/tinned fruit.
Vegetables
  • Brussels sprouts, spinach, silver beet, broccoli
  • Okra, leek, pumpkin, taro leaves
  • Mushrooms
  • Beans, pulses, tomatoes including tomato paste.
  • Bok choy, cabbage, cauliflower
  • Carrot, capsicum, asparagus, eggplant, corn
  • Celery, cucumber, lettuce, peas.
Carbohydrates
(starchy foods)
  • Potato that is not boiled (roasted, baked, fried)
  • Instant potato products, chips, hot chips
  • Green banana
  • Kumara
  • Fruit bread.
  • Boiled potato, taro, cassava, yam
  • Rice
  • Pasta
  • Couscous
  • Noodles, dumplings
  • Chapatti, pitta bread, bread
  • Plain crackers
  • Chinese steamed buns.
Dairy
  • Milk (limit to 300ml per day)
  • Yoghurt
  • Condensed milk, evaporated milk and milk powders
  • Malted milk drinks (eg, Milo)
  • Cheese, crème fraiche or cream
  • Rice or oat milk
Sweets and snacks
  • Fruit cakes, muesli bars
  • Chocolate, fudge, liquorice.
  • Popcorn
  • Unsalted rice crackers.
Cereals
  • Cereals that contain dried fruits, bran, nuts
  • Coco pops, muesli.
  • Porridge or rolled oats made with water
  • Weet-Bix
  • Puffed wheat, Frosties, Special K.
Fluids
  • Fruit and vegetable juices
  • Most alcohols
  • Coffee.
  • Cordial, soft/fizzy drinks
  • Tea.
Other
  • Salt substitutes, eg, 'Lo-salt'
  • Marmite.
  • Honey
  • Jam/marmalade.

Should I take potassium supplements?

A varied and balanced diet should provide you with the potassium you need. It’s important that you tell your doctor or pharmacist before you start potassium supplements. For some people, supplements can be harmful. 

Learn more

The following links provide further information on potassium. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Potassium Kidney Health NZ
Potassium NIH National Institute of Health
Lowering your potassium levels Kidney Care UK

References

Potassium NZ Formulary
A primary care approach to sodium and potassium imbalance BPAC, NZ, 2011
Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes Ministry of Health, NZ, 2019

Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 26 Nov 2021