Chlorothiazide: Uses, side effects, and risks

What is chlorothiazide?

Chlorothiazide is a prescription drug available in the form of a tablet or solution to be taken by mouth. It may also be taken as an injection.

The oral tablets are only available as a generic drug, whereas the oral suspension can be purchased as a brand-name drug called Diuril.

Chlorothiazide may be taken as part of combination therapy with other classes of medication used to control high blood pressure or edema.


Chlorothiazide belongs to a class of drugs called thiazide diuretics. These work in the kidneys to remove sodium and water from the body. This helps to reduce blood pressure, as well as to decrease fluid build-up and swelling.

Side effects

The common side effects of chlorothiazide include:

  • diarrhea
  • more frequent urination
  • loss of appetite
  • dizziness
  • a headache

The body may lose fluid or electrolytes while taking chlorothiazide. Electrolytes need to operate at balanced levels to function correctly. This drug may cause low sodium, low chloride, and low potassium levels in the blood.

Symptoms include:

  • weakness
  • fatigue
  • muscle cramps
  • irregular heart rate
  • confusion
  • seizures
  • coma

Chlorothiazide may raise blood sugar levels. People with diabetes may need to test blood sugar more regularly, and the doctor overseeing diabetes treatment may adjust medications.

Call a doctor if symptoms of high blood sugar become clear, including:

  • intense thirst
  • tiredness
  • blurred vision

Milder side effects of chlorothiazide should resolve without treatment. More severe effects may require intervention from a doctor or pharmacist.

More severe side effects and complications include:

  • Stevens-Johnson syndrome, which can cause flu-like symptoms, aches all over the body, and a red, painful rash that may or may not blister
  • toxic epidermal necrolysis, which can cause severe blistering and peeling of the skin
  • pancreatitis
  • liver and kidney problems
  • lupus, an autoimmune condition that can attack and inflame many parts of the body, causing tiredness, joint pain, a distinctive, butterfly-shaped rash across the middle of the face, and decreased circulation

See a doctor immediately on noticing any of these symptoms. If the drug causes breathing or swallowing difficulties, swelling of the throat or tongue, or hives on the skin, you are experiencing a severe allergic reaction to chlorothiazide that requires emergency treatment.

People with the following conditions should take chlorothiazide[PG2] with caution and discuss the risks with their personal doctor:

  • kidney and liver problems
  • allergy to sulfonamide drugs, or sulfas
  • lupus
  • diabetes
  • gout
  • dehydration

Extra monitoring may be required.

Studies have also shown adverse effects in women who are pregnant, and there is insufficient evidence to confirm whether the medications affect the development of a fetus.

Talk to your doctor when taking chlorothiazide during pregnancy. The benefits of doing so must outweigh any potential fetal risk.


Drinking alcohol while taking chlorothiazide can make the effects of dizziness or faintness worse and is not advised.

Types of medication to use cautiously [PG3] during a course of chlorothiazide include:

  • lithium
  • cholesterol-reducing drugs, such as cholestyramine
  • diabetes medication, including insulin, glimepiride, and glyburide
  • strong pain medications, such as barbiturates and narcotics

In some cases, the dosage of the above medications may require adjustment.

Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, can reduce the effectiveness of chlorothiazide, and corticosteroids, including betamethasone and budesonide, can further impact potassium levels.


The dose of chlorothiazide will vary depending on the following factors:

  • age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

The strength of each dose will be dictated by the product, although the standard starting doses for all forms are as follows:

  • Aged 0 to 5 months: 10 to 30 milligrams (mg) per day taken by mouth in 1 or 2 equally divided doses
  • Aged 6 to 23 months: 10 to 20 mg per day taken by mouth in 1 or 2 equally divided doses
  • Aged 2 to 12 years: 10 to 20 mg per day taken by mouth in 1 or 2 equally divided doses
  • Aged 13 to 17 years: 500 to 1,000 mg by mouth per day in 1 or 2 equally divided doses
  • Aged over 18 years: 500 to 1,000 mg per day taken by mouth in 1 or 2 divided doses

Doctors may prescribe a lower starting dose for people over the age of 65 years. The doctor who prescribed the medicine will monitor symptoms and side effects and adjust the dose where necessary.

Be sure not to exceed the recommended dosage, as this may increase the risk of unwanted side effects.

If you stop this medication your symptoms may return or your blood pressure may not be adequately controlled

Extra information

Here are several extra considerations to bear in mind when transporting, acquiring, or storing chlorothiazide:

  • Take alongside milk or food to reduce the risk of an upset stomach.
  • Do not take the drug before bedtime as it increases urinary frequency.
  • You may cut or crush chlorothiazide to make pills easier to swallow.
  • Do not freeze chlorothiazide.
  • Call the pharmacy ahead of a visit to pick up Diuril. Not all pharmacies stock the solution.
  • If taking chlorothiazide to treat high blood pressure, be sure to monitor blood pressure at home and log the results.
  • You may need to purchase a home blood pressure monitor – click here to find an excellent range, rated by customers [INSERT AFFILIATE LINK].
  • If treatment is for edema, keep track of your weight to gauge fluid buildup.
  • Cut down on salt in the diet, as it can increase both blood pressure and fluid retention, working against chlorothiazide.
  • When traveling, keep this medication at hand. Do not stash it in checked luggage when flying or the glove compartment when driving, and keep the prescription with you. It is usually attached to the box.
  • Shake the oral suspension well before use.

Contact a healthcare professional if you start to notice side effects or note that symptoms are not resolving.

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