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Thiazide diuretic (water tablet): metolazone

Patient information A-Z

What is metolazone and what does it do?

Metolazone is thiazide diuretic or a water tablet. If your heart or kidneys are not working properly water might build up in your body. You might get swollen ankles or feel short of breath. Water tablets help to get rid of the extra water from your body. They help your heart and kidneys to work better.

Why am I prescribed metolazone?

Diuretics or water tablets are used to help your kidneys remove extra fluid. If you have extra fluid in your body, you may notice that you have swollen ankles or difficulty breathing. Diuretics work by helping your kidneys to remove more water and salt from your bloodstream.

Metolazone works together with other diuretics such as furosemide or bumetanide (which your doctor may have prescribed for you before as well) to help to remove extra fluid.

How do I take my metolazone?

Your doctor or pharmacist will explain to you how and when to take your tablets. Always follow the instructions on the label of your medicine very carefully.

You will pass more urine than usual for about four hours after taking the dose.

Do I need to have any tests or be monitored because I am taking metolazone?

Your doctors will monitor your kidneys and the salts such as potassium and sodium in your blood to make sure that you are not loosing too much water and are becoming dehydrated. They may advise you to adjust the doses of your diuretics based on the results of these tests.

Your doctors will also check your weight as this will tell them how much fluid you have lost from your body and will also check your ankles to check for swelling caused by extra fluid.

Are there any side effects?

  • Metolazone can make your blood pressure a bit too low. You might feel dizzy when you first stand up. Take care to stand up slowly and get your balance before setting off walking.
  • Metolazone can cause problems with control of your blood sugar or your blood cholesterol. Your doctor might want to do blood tests to check for this.
  • Metolazone can cause side effects. Tell your doctor if you have problems with:
    • An upset stomach
    • A skin rash or skin which is more sensitive to the effects of the sun

Tell your doctor if you notice any strange effects from taking your metolazone.

Special warnings or precautions you need to be aware of:

Water tablets can make you lose too much water from your body which is known as dehydration. If this happens you will feel thirsty and your mouth will feel dry. If you become dehydrated it is important that you contact your doctor or specialist nurse immediately.

Signs of dehydration include:

  • Feeling thirsty
  • Dry mouth
  • Dry eyes
  • Dry skin

Are there any problems taking thiazide diuretic tablets with any other medications?

If you take lithium tablets the levels of lithium in your blood can be affected by diuretic tablets. If you take lithium please check with your doctor before starting the diuretic tablets.

Only take tablets prescribed for you by your doctor and check with your pharmacist before taking any new medicines.

Further information

Further information about your tablet can be found in the patient information leaflet found in the tablet/capsule box or on the container.

If you have any other questions about your medication, please contact the medicines helpline on 01223 217502.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

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Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151