Understanding your diuretic medicines

Having a good understanding of the medicines you take can help you get the most benefit from them and avoid harm. This brochure provides practical advice for how to safely take your diuretic medicine and what you might need to talk with your GP about.

What are diuretics?

Medicines that you take for heart failure or other heart-related conditions, such as high blood pressure, might include a diuretic medicine.

• Diuretic medicines are often referred to as water or fluid pills because they increase the amount of urine you pass which helps remove retained fluid (water and salt) from your body. Having retained fluid in your body can make you feel breathless and tired, and can cause swelling in your feet and ankles.
• Diuretic medicines also allow muscles in your blood vessels to relax, widening them and making it easier for blood to flow through, which lowers your blood pressure. When prescribed at doses to treat high blood pressure, diuretics don’t have the same effect as when they are prescribed to treat heart failure.

Why do I need monitoring while taking a diuretic?

If you take a diuretic medicine, you will need to see your GP or nurse for blood tests and have your blood pressure checked from time to time

• These blood tests check electrolyte levels (such as potassium and sodium) in your body and your kidney function. If your electrolyte balance is altered, or your kidneys are not functioning properly, you can feel unwell, tired or weak, or have muscle cramps and a headache.
• Your GP will also check your blood pressure. If your blood pressure is too low, it can make you feel dizzy on standing and unsteady on your feet. This can make you more likely to have a fall.
• In some cases, the dose of your diuretic medicine might need to be adjusted.
• Talk with your GP about how often you might need a test to monitor your electrolytes, especially your sodium and potassium levels, and your kidney function. A good time to ask your GP is when your prescription for a diuretic or any other medicine is being renewed. Ongoing monitoring is required while taking a diuretic medicine.

What do I need to know about taking a diuretic medicine?

Your GP or pharmacist will explain the best time to take your diuretic

• If you take a diuretic that substantially increases the amount of urine you pass, such as frusemide (e.g. Lasix), it is generally recommended that you take it in the morning as most people pass urine within an hour of taking it.
• If you take this diuretic twice a day, it is usually best to take the first dose in the morning and the second dose no later than mid-afternoon.
  • If you take this diuretic medicine too late in the day, it might cause you to get up to go to the toilet several times during the night.
• Taking a diuretic on an ‘as needed’ basis is not recommended. Talk with your GP about whether you need a regular dose or whether the diuretic can be stopped.

If you have any concerns about your diuretic medicine, talk with your GP or pharmacist

• Like all medicines, diuretics can cause side effects in some people. Feeling dizzy, particularly when you stand up, can be a side effect of diuretics. If you feel dizzy, get up from your chair or bed gradually. If the dizziness persists, talk with your GP; your diuretic dose might need to be adjusted.
• Always check with your GP or pharmacist before taking any medicines or supplements not prescribed for you, such as products purchased from a supermarket, pharmacy, health food store or online. Some medicines should not be taken with diuretics; for this reason, it is best to talk with your GP first.

Talk with your GP about whether you need to alter what you eat or drink

• Consult your pharmacist or GP before starting any supplements that might contain potassium to see whether they are suitable for you.
• Consuming excess salt might stop your diuretic medicine from working properly. As a general rule, use no more than a teaspoon (6 grams) of salt (sodium chloride) per day. Check with your GP about how much salt is too much for you.

What else do I need to know while taking a diuretic medicine?

Talk with your GP about how much fluid you should have

• If you are taking a diuretic medicine, it can be easier to become dehydrated, especially during hot weather.
• Knowing how much fluid you should have each day can help you stay hydrated. Fluids might come from water, soup, tea and coffee, or foods that have a high water content, such as watermelon, strawberries, oranges, cucumbers and tomatoes.
• Talk with your GP about how much fluid you should have on hot days.
• In some cases, your GP might suggest you take a lower dose of your diuretic or temporarily stop taking your diuretic on hot days.
• If you are feeling dehydrated (see Box 1 for common signs) for more than two days or your symptoms worsen, call your GP practice or go to your closest emergency department.

Have a plan for what to do if you become unwell with fever, vomiting or diarrhoea

• Talk with your GP about situations when you might need to temporarily stop taking your diuretic medicine. For example, if you are unwell with symptoms such as vomiting, diarrhoea or fever you might be at a higher risk of becoming dehydrated. Your GP might suggest you stop taking your diuretic until you are eating and drinking normally again.

Keep an up-to-date list of your medicines that you can access easily

• Take your medicines list with you whenever you visit your GP, pharmacist and other healthcare team members. This will help you identify your diuretic medicines that might be packed in a dose administration aid or as a single-dose combination tablet.
• If you don’t have a medicines list, ask your pharmacist for an up-to-date list or download the free MedicineWise app at: www.nps.org.au/medicinewiseapp

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