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Chlortalidone 12.5 mg, 25 mg and 50 mg tablets – patient leaflet, side effects, dosage

Last updated: · Text from the MHRA, as of · About this document

Medicine strength:
25 mg
Contains active substance:

Patient leaflet - Chlortalidone 25 mg tablets

1. What Chlortalidone tablets are and what they are used for

Chlortalidone tablets belong to a group of medicines called thiazide diuretics.

Thiazide diuretics help to reduce the amount of water in your body. They do this by increasing the amount of water that you pass as urine. They are sometimes called ‘water tablets’.

Chlortalidone tablets are used to:

  • treat high blood pressure (hypertension)
  • treat heart failure
  • help reduce the fluid retention that occurs

    with some kidney or liver diseases

  • treat diabetes insipidus (a condition in which

    an individual produces large amounts of dilute urine and is constantly thirsty)

2. What you need to know before you take Chlortalidone tablets

Do not take Chlortalidone tablets:

  • if you are allergic to Chlortalidone or

    sulphonamides such as sulfamethoxazole or any of the other ingredients of this medicine (see Section 6. Contents of the pack and other information)

  • if you are not passing any urine at all
  • if you have severe kidney or liver problems
  • if you have low blood levels of potassium

    which can cause muscle weakness, muscle twitching or abnormal heartbeat

  • if you have low blood levels of sodium

    which can cause tiredness, confusion, muscle twitching, fits or coma

  • if you have high blood levels of calcium

    which can cause loss of appetite, tiredness or muscle weakness

  • if you have ever had gout or kidney stones
  • if you have Addison’s disease (which is a

    condition where your adrenal gland is not producing enough steroids)

  • if you are taking lithium

If any of the above applies to you, or if you are not sure, speak to your doctor or pharmacist before you take Chlortalidone tablets. Warnings and precautions

Talk to your doctor, pharmacist or nurse before taking Chlortalidone tablets:

  • if you suffer from any other liver or kidney

    problems

  • if you are on a low-salt diet
  • if you suffer from diabetes mellitus (increased

    levels of sugar in the blood)

  • if you have high cholesterol levels
  • if you have recently had an anaesthetic
  • if you are elderly
  • if you experience a decrease in vision or

    eye pain. These could be symptoms of fluid accumulation in the vascular layer of the eye (choroidal effusion) or an increase of pressure in your eye and can happen within hours to a week of taking Chlortalidone tablets. This can lead to permanent vision loss, if not treated. If you earlier have had a penicillin or sulphonamide allergy, you can be at higher risk of developing this.

If any of the above applies to you, or if you are not sure, speak to your doctor or pharmacist before you take Chlortalidone tablets. Other medicines and Chlortalidone tablets

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. This applies to medicinal products subject to medical prescription or those obtained without prescription, especially:

  • other treatments for high blood pressure or

    heart problems such as:

    • ACE inhibitors (for example, lisinopril)
    • beta blockers (for example propranolol hydrochloride)
    • methyldopa
    • vasodilators (for example bosentan)
    • calcium channel blockers (for example amlodipine)
    • guanethidine
    • corticosteroids such as prednisolone or betamethasone – used to treat allergic and inflammatory diseases and immune reactions
    • adrenocorticotropic hormone (ACTH) – used to treat a number of different conditions, including ulcerative colitis (a form of inflammatory bowel disease), Crohn’s disease (a form of chronic inflammatory bowel disease) and rheumatoid arthritis
    • cytotoxic agents such as cyclophosphamide or methotrexate – used to treat cancer
    • asthma treatments such as salbutamol or formoterol
    • amphotericin – used to treat infections
    • carbenoxolone – used to treat ulcers
    • insulin and other treatments for diabetes such as chlorpropamide or glibenclamide
    • digoxin – for an irregular heartbeat
    • lithium – used to treat mental illness
    • anticholinergics such as atropine sulphate or hyoscine (butylbromide) – for abdominal or stomach spasms or cramps
    • colestyramine – used to reduce cholesterol levels and prevent heart disease
    • amantadine – used to treat Parkinson’s disease or viral infections
    • allopurinol – used to treat gout (a complex type of arthritis)
    • non-steroidal anti-inflammatories (NSAIDs)

      such as aspirin or indometacin – used for pain relief or rheumatism

    • ciclosporin – used to treat rheumatic disease or skin complaints or after a transplant
    • calcium salts or vitamin D – used for

      replacement therapy

Please tell your doctor or pharmacist if you are taking or have recently taken/used any other medicines, including medicines obtained without a prescription.

Chlortalidone tablets with food, drink and alcohol

It is best to take Chlortalidone tablets in the morning with food. Swallow your tablets whole with a drink of water.

You should avoid low salt diets. Taking Chlortalidone tablets may reduce the amount of salt in your body.

If you are on a low salt diet check with your doctor first before taking Chlortalidone tablets. Pregnancy and breast-feeding

If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.

Pregnancy

Do not take Chlortalidone tablets if you are pregnant or trying to become pregnant. Tell your doctor, immediately, if you become pregnant during treatment with Chlortalidone tablets. Breast-feeding

Do not take Chlortalidone tablets if you are breast-feeding because the active substance of Chlortalidone tablets passes into breast milk and could harm your baby.

Driving and using machines

Chlortalidone tablets may cause dizziness. If you feel dizzy when you start taking these tablets, do not drive or work with machinery until these effects have worn off.

Chlortalidone tablets contain lactose

Chlortalidone tablets contain a sugar called lactose. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product. This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially sodium-free.

3. How to take Chlortalidone tablets

Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. Your doctor will choose a suitable starting dose for your particular condition and monitor your progress. If necessary, this dose can be increased or reduced.

Whilst you are taking Chlortalidone tablets, your doctor may want to carry out a number of tests from time to time. This is quite usual and nothing to worry about.

It is best to take Chlortalidone tablets in the morning with food. Swallow your tablets whole with a drink of water.

The tablet can be divided into equal doses (25 mg and 50 mg tablets only).

Adults

The usual doses for adults are as follows:

  • High blood pressure:

    The starting dose is 25 mg a day. Your doctor may increase this to 50 mg a day

    if necessary.

  • Heart failure:

    The starting dose is 25 mg a day. Your doctor may increase this up to 200 mg

    (four 50 mg tablets) a day if necessary.

  • Fluid retention associated with kidney or liver disease:

    Up to 50 mg a day.

  • Diabetes insipidus (a disease in which an individual produces large amounts of dilute urine and is constantly thirsty):

    The starting dose is 100 mg (two 50 mg

    tablets) twice a day. Your doctor may reduce your dose to 50 mg (one 50 mg tablet) a day. Children

Your doctor will choose a suitable dose based on your child’s age and weight.

Elderly patients or those with kidney problems

Your doctor may give you a lower dose because your body may not get rid of Chlortalidone tablets as quickly as normal.

If you are not sure how many tablets to take, ask your doctor or pharmacist. Do not stop taking your tablets suddenly. Ask your doctor first. If you take more Chlortalidone tablets than you should

If you accidentally take more Chlortalidone tablets than you should, tell your doctor immediately or contact your nearest accident and emergency department. Show any left-over medicines or the empty packet to the doctor. If you forget to take Chlortalidone tablets

If you forget to take a dose, take it as soon as possible, unless it is almost time to take the next dose. Do not take a double dose. Then go on as before.

If you have any further questions on the use of this medicine, ask your doctor, pharmacist or nurse.

4. Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them. If you get any of the following effects tell your doctor or pharmacist immediately:

Very common (may affect more than 1 in 10 people):

  • low blood levels of potassium which can

    cause muscle weakness, muscle twitching or abnormal heartbeat

  • increased blood levels of uric acid
  • increased blood levels of cholesterol Common (may affect up to 1 in 10 people):
  • low levels of sodium which can cause

    tiredness, confusion, muscle twitching, fits or coma

  • low levels of magnesium
  • high blood sugar levels which can cause

    tiredness, weakness or feeling thirsty

  • nettle rash
  • skin rash
  • low blood pressure which may make you feel

    dizzy when you stand up

  • dizziness
  • loss of appetite
  • upset stomach
  • impotence in men

Rare (may affect up to 1 in 1,000 people):

  • increased calcium in the blood which can

    cause agitation, sore eyes, abdominal pain

  • sugar in the urine (this would show up when

    your doctor or nurse tests your urine)

  • worsening of diabetes
  • yellowing of the skin or eyes caused by liver

    or blood problems (jaundice)

  • increased sensitivity of your skin to sunlight
  • abnormal heartbeat the symptoms of which

    include palpitations and fainting

  • pins and needles
  • headache
  • feeling or being sick
  • stomach pain
  • constipation
  • diarrhoea
  • reduction in blood platelets which increases

    the risk of bruising or bleeding

  • severe reduction in the number of white blood

    cells which makes infection more likely

  • an abnormally high amount of eosinophils

    (type of white blood cell) in the blood

  • breathing problems
  • problems with your kidneys

Uncommon (may affect up to 1 in 100 people):

  • gout which causes pain and swelling in the

    joints

    Very rare (may affect up to 1 in 10,000 people):

    • low levels of chloride in the blood, symptoms include dry mouth, thirst, gastrointestinal disturbances (including nausea, vomiting), weakness, lethargy, drowsiness, restlessness, seizures, confusion, headache, muscle pains or cramps, hypotension
    • inflammation of the pancreas which causes severe stomach and back pain

Frequency unknown:

  • decrease in vision or pain in your eyes due to high pressure (possible signs of fluid accumulation in the vascular layer of the eye (choroidal effusion) or acute angle-closure glaucoma)

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store Chlortalidone tablets

This medicinal product does not require any special storage conditions.

Keep this medicine out of the sight and reach of children.

Do not use this medicine after the expiry date which is stated on the carton after ‘EXP’. The expiry date refers to the last day of that month.

Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.

6. Contents of the pack and other information

What Chlortalidone tablets contain

The active substance is Chlortalidone Chlortalidone 12.5 mg tablet: Each tablet contains 12.5 mg of chlortalidone

Chlortalidone 25 mg tablet: Each tablet contains 25 mg of chlortalidone

Chlortalidone 50 mg tablet: Each tablet contains 50 mg of chlortalidone

The other ingredients are: cellulose

microcrystalline, lactose monohydrate, sodium starch glycolate (Type A), povidone K30, silica colloidal anhydrous, magnesium stearate, purified water

What Chlortalidone tablets look like and contents of the pack

Chlortalidone 12.5 mg tablets are:

White to off-white, round shaped (diameter 5.60 mm approx.), flat uncoated tablet engraved with Y on one side and 37 on other side. Chlortalidone 25 mg tablets are:

White to off-white, round shaped (diameter 7.00 mm approx.), flat uncoated tablets with plain on one side and on other side engraved with Y and 53 on either side of the break line Chlortalidone 50 mg tablets are:

White to off-white, round shaped (diameter 8.30 mm approx.), flat uncoated tablets with plain on one side and on other side engraved with Y and 55 on either side of the break line Chlortalidone 12.5 mg tablets are available in PVC/PVDC or Alu-Alu blister packs of 20, 30, 50 and 100 tablets.

Chlortalidone 25 mg tablets are available in PVC/PVDC or Alu-Alu blister packs of 20, 30, 50 and 100 tablets.

Chlortalidone 50 mg tablets are available in PVC/PVDC or Alu-Alu blister packs 20, 30, 50 and 100 tablets.

Not all pack sizes may be marketed. Marketing Authorisation Holder and Manufacturer

Marketing Authorisation Holder

Glenmark Pharmaceuticals Europe Limited Laxmi House, 2-B Draycott Avenue

Kenton, Middlesex

HA3 0BU

United Kingdom

Manufacturer

Glenmark Pharmaceuticals Europe Limited Building 2, Croxley Green Business Park Croxley Green, Hertfordshire

WD18 8YA, United Kingdom

Glenmark Pharmaceuticals s.r.o.

Fibichova 143

56617 Vysoké Mýto

Czech Republic

This leaflet was last revised in August 2024

About this document

Source: MHRA - Medicines and Healthcare products Regulatory Agency (products.mhra.gov.uk) · Marketing authorisation: PL 25258/0400

Last revision stated in the text: August 2024 · MHRA data as of 13 October 2026

Found a mistake? Tell us on the contact page.

The information on this site does not replace the advice of a doctor or pharmacist.

Facts about Chlortalidone 25 mg tablets

Active substance Chlortalidone
Strength 25 mg
Pharmaceutical form Oral tablet
White to off-white, round shaped (diameter 7.00 mm approx.), flat uncoated tablet with plain on one side and on other side engraved with Y and 53 on either side of the break line.
The tablet can be divided into equal doses.
How is it taken Oral
Excipients Cellulose, microcrystalline, Lactose monohydrate, Sodium starch glycolate (Type A), Povidone K30, Silica, colloidal anhydrous, Magnesium stearate, Purified water
Is it available? Listed as available (NHS Dictionary of Medicines and Devices – not a record of current supplies)
Shelf life 2 years
Storage This medicinal product does not require any special storage conditions
Drug group (ATC)
  1. C Cardiovascular system drugs
    1. C03 Diuretics
      1. C03B Low-ceiling diuretics, excl. thiazides
        1. C03BA Sulfonamides, low-ceiling diuretics, plain
          1. C03BA04 chlortalidone
Marketing authorisation PL 25258/0400 (first authorised 3 October 2024)
Marketing authorisation holder Glenmark Pharmaceuticals Europe Limited Laxmi House, 2-B Draycott Avenue

Sources: the MHRA product information (products.mhra.gov.uk) and the NHS Dictionary of Medicines and Devices (dm+d), release 10.1.0 of 12 October 2026, NHS Business Services Authority. Contains public sector information licensed under the Open Government Licence v3.0.