This medication is used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Hydrochlorothiazide belongs to a class of drugs known as diuretics/"water pills." It works by causing you to make more urine. This helps your body get rid of extra salt and water.

This medication also reduces extra fluid in the body (edema) caused by conditions such as heart failure, liver disease, or kidney disease. This can lessen symptoms such as shortness of breath or swelling in your ankles or feet.

Take this medication by mouth as directed by your doctor, usually once daily in the morning with or without food. If you take this drug too close to bedtime, you may need to wake up to urinate. It is best to take this medication at least 4 hours before your bedtime.

The dosage is based on your medical condition and response to treatment.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. Keep taking this medication even if you feel well. Most people with high blood pressure do not feel sick.

If you also take certain drugs to lower your cholesterol (bile acid-binding resins such as cholestyramine or colestipol), take hydrochlorothiazide at least 4 hours before or at least 4 to 6 hours after these medications.

Tell your doctor if your condition does not get better or if it gets worse (for example, your blood pressure readings remain high or increase).

Upset stomach, dizziness, or headache may occur as your body adjusts to the medication. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication may cause dehydration and electrolyte imbalance. Tell your doctor right away if you have any symptoms of dehydration or electrolyte imbalance, including unusual dry mouth/thirst, muscle cramps/weakness, slow/fast/irregular heartbeat, or confusion.

Tell your doctor right away if you have any serious side effects, including:

• fainting
• signs of kidney problems (such as change in the amount of urine)
• decrease in vision
• eye pain

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking hydrochlorothiazide, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients (such as sulfites found in some brands), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• diabetes
• gout
• kidney disease
• liver disease
• lupus
• skin cancer

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Severe sweating, diarrhea, or vomiting may cause dehydration and cause you to feel lightheaded. Tell your doctor if you have severe diarrhea or vomiting. To prevent dehydration, drink plenty of fluids unless your doctor tells you not to.

If you have diabetes, hydrochlorothiazide may affect your blood sugar. Check your blood sugar regularly as directed by your doctor. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

This drug may decrease your potassium levels. Ask your doctor about foods high in potassium (such as bananas, orange juice) or about using a salt substitute containing potassium. A potassium supplement may be prescribed by your doctor.

This medication may make you more sensitive to the sun. It may also increase your risk for skin cancer, especially if you take it for a long time. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned, have skin blisters/redness, or notice new or changed moles/skin lesions.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the effects of this drug, especially dizziness.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This drug passes into breast milk, but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.

See also How To Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• dofetilide
• lithium

Some products have ingredients that could raise your blood pressure or worsen your swelling. Tell your pharmacist what products you are using, and ask how to use them safely (especially cough-and-cold products, diet aids, or NSAIDs such as ibuprofen/naproxen).

This medication may interfere with certain lab tests (such as parathyroid function), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, weakness, fainting.

Do not share this medication with others.

Lifestyle changes that may help this medication work better include exercising, stopping smoking, and eating a low-cholesterol/low-fat diet. Consult your doctor for more details.

Lab and/or medical tests (such as potassium levels, kidney function, skin exams) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

Check your blood pressure and pulse (heart rate) regularly while taking this medication. Learn how to check your own blood pressure and pulse at home, and share the results with your doctor.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.