Sounds like 'klor-THAL-i-done'

Easy-to-read medicine information about chlortalidone – what it is, how to take chlortalidone safely and possible side effects.

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 causes you to pass out more urine from your kidneys. It helps your body to get rid of extra salt and water.
  • It 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.
  • Chlortalidone is available as tablets.


  • The usual dose of chlortalidone for high blood pressure is 12.5 milligrams or 25 milligrams once a day.
  • The usual dose for the treatment of oedema (excess fluid) is 25 milligrams taken once a day. Some people may require higher doses.
  • 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 that day. However, if it is after 6 pm in the evening, you should skip the forgotten dose and continue as usual the next day. Do not take double the dose.

Possible side effects

Like all medicines, chlortalidone can cause unwanted side effects, although not everyone gets them. Often unwanted 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 chlortalidone, and usually go away after the first few days
  • Tell your doctor if troublesome
  • Dizziness
  • Feeling light headed
  • Feeling faint when you stand up
  • Be careful when getting up from either lying down or sitting to avoid falls. These effects puts you at risk of falls and injuries, especially if your 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 (loosing 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


Chlortalidone may interact with a number of  medications and herbal supplements so check with your doctor or pharmacist before starting chlortalidone or before starting any new medicines. Also check with your pharmacist before taking anti-inflammatories that can be bought over-the-counter, such as diclofenac (e.g. Voltaren Rapid), ibuprofen (e.g. Nurofen), naproxen (e.g. Naprogesic).

Learn more

The following links provide further information on chlortalidone.

Medsafe Consumer Information Sheets: Hygroton

New Zealand Formulary Patient Information: Chlortalidone

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ Last reviewed: 19 Oct 2015