Diuretics

Also called 'water pills' or 'water tablets'

Diuretics are medicines that help your body get rid of extra salt (sodium) and water. They work by increasing the amount of urine (pee) you make.

Diuretics are used to treat conditions like high blood pressure (hypertension) and swelling (oedema) in your feet, ankles and stomach caused by heart failure, kidney failure or liver failure

How do diuretics work?

Diuretics help your body get rid of extra salt (sodium) and water. They work by increasing the amount of urine (pee) you make. Getting rid of extra water decreases the strain on your heart and blood vessels, by lowering blood pressure. This effect can also improve symptoms such as trouble breathing and swelling (oedema). Diuretics are often called ‘water tablets’.

Be careful when taking some pain relief medicines
Taking diuretics together with pain relief medicines called ‘non-steroidal anti-inflammatory drugs’ (NSAIDs) and medicines called ACE inhibitors or ARBs can be harmful to your kidneys (this combination of medicines is called the triple whammy). Read more: Be careful when taking some pain relief medicines

Which diuretics are available in New Zealand?

There are a few classes or types of diuretics available in New Zealand: loop, thiazide and potassium-sparing. Each type affects a different part of your kidneys and may have different uses. Your doctor will discuss which diuretic is best for you – this usually depends on your health and the condition being treated. 

Class of diuretic Examples
Loop diuretics
Thiazide diuretics
Potassium-sparing diuretics

Tips for taking diuretics

Time your doses

When you first start taking diuretics, you will pee (urinate) more often and in larger amounts. This will lessen after you have taken the medication for a while. Because diuretics cause you to pee more often, most people prefer to take it in the morning. Some people may need a second dose at lunchtime. 

  • You will get to know how long it takes for your diuretic tablet to work after you have started staking it, then you can plan your day around it. 
  • If you want to go out in the morning and don't want to have to find a toilet, you can delay taking your dose until lunchtime or early afternoon. 
  • Avoid taking your dose within 4 hours of your bedtime to prevent having to get up often to urinate during the night.

Weigh yourself

If you are taking your diuretic for heart failure, the best way to know if it is working is to weigh yourself at the same time each day. Read more about medicines for heart failure

Limit alcohol

Limit or avoid drinking alcohol while you are taking your diuretic. Alcohol may increase your chances of getting side effects such as dizziness.

Have regular blood and urine tests

You may need regular blood and urine tests to check potassium and blood glucose levels. This is to make sure that all the chemicals in your bloodstream are properly balanced.

Precautions – before starting diuretics

  • Are you pregnant or breastfeeding?
  • Do you have difficulty peeing, or do you have prostate problems?
  • Do you have gout or diabetes? These conditions can be made worse by diuretics.
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines and medicines you can buy for pain relief.

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

Possible side effects

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

Side effects What should I do?
  • Dizziness
  • Feeling lightheaded
  • Feeling faint when you stand up
  • Be careful when getting up from either lying down or sitting to avoid falls. These effects put you at risk of falls and injuries, especially if you are elderly
  • Be careful when driving or using tools until you know how this medicine affects you
  • Signs of dehydration (loosing too much salt and water) such as muscle cramps, weakness, dry mouth, thirst or passing reduced amounts of urine
  • Tell your doctor
  • Signs of an allergic reaction such as skin rashes, itching, blisters, peeling skin, swelling of the face, lips, mouth or have problems breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116

Interactions

Diuretics can interact with a number of other medicines and herbal supplements so check with your doctor or pharmacist before starting diuretics or before starting any new medicines.

Be careful when taking some pain relief medicines

Taking the group of pain relief medicines called ‘non-steroidal anti-inflammatory drugs’ (NSAIDs) can be harmful to your kidneys. Examples include: 

Taking NSAIDs together with diuretics and medicines called ACE inhibitors or ARBs can be harmful to your kidneys (this combination of medicines is called the triple whammy). If you are taking ACE inhibitors or ARBs and diuretics, tell your doctor or pharmacist before starting NSAIDs.

  • Examples of ACE inhibitors are captopril, cilazapril, enalapril, lisinopril, perindopril and quinapril.
  • Examples of ARBs are candesartan, irbesartan, valsartan and losartan.

Before buying NSAIDs for pain relief, check with your pharmacist whether these are safe for you.

Read more about NSAIDs, ACE inhibitors, ARBs and The triple whammy SafeRx

Learn more

The following links have more information on diuretics. Be aware that websites from other countries may contain information that differs from New Zealand recommendations. 

Loop diuretics Patient Info, UK
Thiazide diuretics Patient Info, UK
Potassium-sparing diuretics Patient Info, UK

References

  1. Diuretics New Zealand Formulary
Credits: Sandra Ponen, pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 01 Feb 2019