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Thiazide diuretic (water pill)

Hydrochlorothiazide: uses, side effects & precautions

Also known as Microzide, Esidrex, HydroDIURIL, HCTZ.

Ces informations sont fournies à titre indicatif uniquement et ne constituent pas un avis médical. Consultez toujours un professionnel de santé qualifié pour toute préoccupation médicale personnelle. En cas d'urgence, appelez votre numéro d'urgence local.

What it is used for

  • High blood pressure (hypertension)
  • Fluid retention (oedema) from heart, liver, or kidney conditions

How it works

Hydrochlorothiazide helps the kidneys remove extra salt and water from the body through urine. This lowers the volume of fluid in the blood vessels and relaxes them over time, which reduces blood pressure.

How it is taken

Taken by mouth as a tablet or capsule, usually once a day. It is often taken in the morning so that increased urination does not disturb sleep. Take it exactly as your doctor or pharmacist directs and follow the label; your clinician may check your blood salts and kidney function periodically.

No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.

Common side effects

  • Passing more urine, especially at first
  • Dizziness or light-headedness
  • Low blood potassium or sodium (may cause weakness or cramps)
  • Increased thirst
  • Raised blood sugar or uric acid in some people
  • Increased sensitivity to sunlight

Serious effects — get help

  • Severe dizziness or fainting
  • Muscle weakness, severe cramps, or irregular heartbeat (signs of salt imbalance)
  • Signs of a serious allergic or skin reaction such as rash, blistering, or trouble breathing
  • Sudden eye pain or vision changes
  • A gout attack in people prone to gout

If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.

Interactions to watch

  • Other blood pressure medicines (additive effect)
  • Lithium (levels can rise)
  • Non-steroidal anti-inflammatory drugs such as ibuprofen (may reduce effect)
  • Other medicines that lower potassium, such as some steroids
  • Diabetes medicines (blood sugar may change)

Who should take care

  • Tell your clinician about gout, diabetes, kidney, or liver problems
  • Discuss pregnancy or breastfeeding with your doctor
  • Stay hydrated but follow any fluid advice you are given
  • Use sun protection, as the medicine can increase sunburn risk
  • Report ongoing muscle cramps, weakness, or unusual tiredness

Frequently asked questions

Why do I need to urinate more often?
Hydrochlorothiazide works by helping your kidneys remove extra salt and water, so increased urination is expected, especially early on. Taking it in the morning helps avoid night-time trips.
Do I need extra potassium?
The medicine can lower potassium for some people. Your clinician may check your blood and advise on diet or a supplement — do not start one on your own.
Can it affect my blood sugar or gout?
It can raise blood sugar and uric acid in some people. Tell your clinician if you have diabetes or gout so they can monitor you.
Should I drink less water?
Not unless your clinician tells you to. Follow any specific fluid advice you are given and report excessive thirst or dizziness.
Is Hydrochlorothiazide safe to take?
For most people it is safe when taken exactly as a doctor or pharmacist advises and as printed on the label. Tell your clinician about your other medicines and health conditions, and seek urgent care for any serious reaction.

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