How does this medication work? What will it do for me?

Hydrochlorothiazide belongs to the group of medications called diuretics. It is also an antihypertensive. It is used to decrease fluid retention (edema) caused by congestive heart failure, certain kidney or liver problems, and medications such as corticosteroids (e.g., prednisone) and estrogen. It is also used to lower high blood pressure. Hydrochlorothiazide works by making the body lose excess water and salt.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

25 mg
Each round, peach, scored tablet with "PRO" over "25" on one side contains hydrochlorothiazide 25 mg. Nonmedicinal ingredients: colloidal silicon dioxide, FD&C Yellow No. 6, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and corn starch.

How should I use this medication?

To reduce fluid retention (edema), the usual recommended adult dose of hydrochlorothiazide is 25 mg to 200 mg daily. Some people may only need to take this medication every other day, or for 3 to 5 days per week, as directed by their doctor. For infants and children, the dose is based on body weight and is given in 2 divided doses.

For the treatment of high blood pressure, the usual recommended adult dose of hydrochlorothiazide is 12.5 mg to 50 mg daily.

When taken once daily, this medication should be taken in the morning to prevent the need to urinate during nighttime.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take hydrochlorothiazide if you:

  • are allergic to hydrochlorothiazide, sulfonamide medications (e.g., sulfamethoxazole), or any of the ingredients of the medication
  • are unable to urinate
  • have kidney disease that is worsening and reduced urine production while taking this medication

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • constipation
  • decreased sexual ability
  • diarrhea
  • dizziness or lightheadedness when getting up from a lying or sitting position
  • headache
  • increased sensitivity of skin to sunlight (skin rash, itching, redness, other discoloration of skin, or severe sunburn after exposure to sunlight)
  • nausea
  • loss of appetite
  • upset stomach
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • black, tarry stools
  • blistering, peeling skin
  • blood in urine or stools
  • cough
  • joint pain
  • lower back or side pain
  • painful or difficult urination
  • pinpoint red spots on skin
  • signs of too much potassium loss (dryness of mouth, increased thirst, irregular heartbeat, mood or mental changes, muscle cramps or pain, nausea or vomiting, unusual tiredness or weakness, weak pulse)
  • signs of too much sodium loss (confusion, convulsions, decreased mental activity, irritability, muscle cramps, unusual tiredness or weakness)
  • skin rash or hives
  • stomach pain (severe) with nausea and vomiting
  • tingling or burning sensation
  • unusual bleeding or bruising
  • vision changes
  • yellow eyes or skin

Seek immediate medical attention if any of the following occur:

  • difficulty breathing (sudden)
  • fever and chills
  • hoarseness

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Cholesterol: Increases in cholesterol and triglyceride levels may occur when taking hydrochlorothiazide. Your doctor will monitor your cholesterol and triglyceride levels with blood tests while you are taking this medication.

Diabetes: Hydrochlorothiazide may make it more difficult for people with diabetes to control their blood sugar. If you have diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Fluid and electrolyte balance: The levels of electrolytes such as potassium, sodium, magnesium, and chloride can be reduced with hydrochlorothiazide. Your doctor will monitor your electrolyte levels with blood tests while you are taking this medication. Warning signs or symptoms of fluid and electrolyte imbalance include:

  • confusion
  • drowsiness
  • dry mouth
  • low blood pressure
  • muscle pains or cramps
  • muscular fatigue
  • nausea and vomiting
  • racing heartbeat
  • restlessness
  • seizures
  • thirst
  • unusual tiredness
  • weakness

If you experience any of these symptoms, contact your doctor. To prevent low potassium levels, eat foods that are high in potassium (e.g., bananas, dried figs, dates, prunes, nuts). If your potassium level is low, your doctor may suggest a potassium supplement.

Gout: This medication may aggravate or cause gout. People with high levels of uric acid in the blood or a history of gout should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney function: If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver disease: If you have reduced liver function or progressive liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Low blood pressure when standing: This medication can cause low blood pressure when standing from a sitting or lying position (also called orthostatic hypotension). Alcohol and other medications such as phenobarbital and other medications to treat high blood pressure can increase the chances that this will happen. If you are taking these medications, your doctor may change the dose of these medications and increase them slowly to reduce the chance of you experiencing this.

Systemic lupus erythematosus: This medication can worsen or activate the symptoms of lupus. If you experience swollen and painful joints, fever, fatigue, or rash on the nose and cheeks while taking this medication, contact your doctor.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking hydrochlorothiazide, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

What other drugs could interact with this medication?

There may be an interaction between hydrochlorothiazide and any of the following:

  • alcohol
  • allopurinol
  • amphotericin B
  • anesthetics
  • anticholinergic medications (e.g., oxybutinin)
  • barbiturates (e.g., phenobarbital)
  • calcium supplements
  • cholestyramine
  • colestipol
  • corticosteroids (e.g., prednisone) and ACTH
  • digoxin
  • insulin
  • lithium
  • medications that lower blood pressure
  • medications that reduce potassium levels (e.g., other diuretics such as furosemide)
  • narcotics (e.g., codeine, oxycodone, morphine)
  • nonsteroidal anti-inflammatory drugs (NSAIDS; e.g., ibuprofen, naproxen, diclofenac)
  • norepinephrine
  • oral diabetes medications (e.g., glyburide, gliclazide, metformin, pioglitazone)
  • pseudoephedrine
  • quinidine
  • rituximab
  • tetracyclines (e.g., tetracycline, minoclycline, doxycycline)
  • topiramate
  • warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.