Sounds like 'klor-THAL-i-done'

Chlortalidone is a diuretic, which means it helps your body get rid of extra salt (sodium) and water. Find out how to take it safely and possible side effects. Chlortalidone is also called Hygroton.

Type of medicine Also called
  • Diuretic (causes you to pass more urine)
  • Thiazide diuretic
  • 'Water' tablet or 'water pill'
  • Hygroton®
  • Chlorthalidone

What is chlortalidone?

Chlortalidone is a diuretic, which means it helps your body get rid of extra salt (sodium) and water. It works by increasing the amount of urine (pee) you make. Chlortalidone is used to treat high blood pressure (hypertension), and is also used to lessen extra fluid in the body (called oedema) caused by conditions such as heart failure, liver disease, or kidney disease. This can reduce symptoms such as swelling in your ankles or feet, or shortness of breath. In New Zealand, chlortalidone is available as tablets (25 mg). 


  • High blood pressure: the usual dose is half to one tablet (12.5 mg to 25 mg) a day.
  • Oedema (excess fluid): the usual dose is 25 mg once a day. Some people may need higher doses.
  • Your doctor will advise you how long to take chlortalidone for.
  • Always take your chlortalidone exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much chlortalidone to take, how often to take it, and any special instructions.

How to take chlortalidone

  • Take chlortalidone once a day, in the morning. 
  • It is best taken in the morning, so it works during the day and your sleep is not disturbed by you needing to get up to go to the toilet during the night.
  • You can take chlortalidone with or without food.
  • Limit or avoid drinking alcohol while you are taking chlortalidone. Alcohol may increase your chances of getting side effects such as dizziness.
  • If you forget to take your dose, take it as soon as you remember. But, if it is late in the afternoon, skip the missed dose and continue as usual the next day. Do not take double the dose.
Be careful when taking some pain relief medicines
Taking diuretics together with pain relief medicines called ‘non-steroidal anti-inflammatory drugs’ (NSAIDs), such as ibuprofen and diclofenac and medicines called ACE inhibitors or ARBs can be harmful to your kidneys. Read more about NSAIDs and blood pressure medicines.

What to consider before starting chlortalidone

  • Are you pregnant or breastfeeding?
  • Do you have difficulty peeing, or do you have prostate problems?
  • Do you have problems with your liver or kidneys?
  • Do you have gout or diabetes? These conditions can be made worse by bendroflumethiazide.
  • 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 chlortalidone. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of chlortalidone?

Like all medicines chlortalidone can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Feeling sick (nausea)
  • Stomach upset

  • These are quite common when you first start taking chlorthalidone, and usually go away after the first few days
  • Tell your doctor if troublesome
  • 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 and symptoms of gout
  • Chlortalidone may raise serum uric acid levels and cause an acute attack of gout in some people
  • Tell your doctor
  • Signs of dehydration (losing too much salt and water) such as muscle cramps, weakness, dry mouth, thirst or passing unusually 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
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


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 chlortalidone.

Medsafe Consumer Information Sheets: Hygroton 
New Zealand Formulary Patient Information: Chlortalidone


  1. Chlortalidone New Zealand Formulary

Additional resources for healthcare professionals

Interactions checker NZ Formulary
Hygroton Medsafe, NZ
How low can the potassium and sodium go with commonly prescribed blood pressure medications? Tools for Practice Alberta College of Family Physicians (ACFP), Canada, 2016
Hypertension in adults – the silent killer BPAC, NZ, 2013

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 13 Feb 2019