What is Hydrochlorothiazide: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Hydrochlorothiazide is a prescription drug used to treat high blood pressure and fluid buildup (edema). As a diuretic (“water pill”), hydrochlorothiazide increases the amount of water and salt that are eliminated from the body through urination, helping to lower blood pressure and eliminate excess fluid. Because of its effectiveness and relative safety, hydrochlorothiazide has been a mainstay of blood pressure treatment for over 60 years.

Hydrochlorothiazide overview

BRAND NAMES:

  • No brand-name versions currently available

Generic Names:

  • Hydrochlorothiazide

Uses:

  • Treats high blood pressure and fluid retention (edema). This medicine is a diuretic (water pill).

Therapeutic Classes:

  • Diuretic, thiazide diuretic, antihypertensive

Forms:

  • Capsule, tablet

How it’s taken:

  • By mouth

What is Hydrochlorothiazide used for?

Hydrochlorothiazide is primarily used alone or with other drugs to control high blood pressure (hypertension). It’s also used along with other drugs to treat body fluid accumulation (edema) due to certain conditions such as heart failure, liver problems, or kidney dysfunction.

What form(s) does Hydrochlorothiazide come in

  • Tablet

    • 12.5 mg

    • 25 mg

    • 50 mg

  • Capsule

    • 12.5 mg

What are common Hydrochlorothiazide doses?

  • For high blood pressure in adults: 25–50 mg taken daily as a single dose or as two divided doses

  • For edema in adults: 25–100 mg taken daily as a single dose or as two divided doses 

  • For edema in children: 0.5–1 mg/lb taken daily as a single dose or as two divided doses

Common Hydrochlorothiazide prescriptions

  • hydroCHLOROthiazide
    12.5mg capsule

  • hydroCHLOROthiazide
    12.5mg tablet

  • hydroCHLOROthiazide
    25mg tablet

  • hydroCHLOROthiazide
    50mg tablet

How to take Hydrochlorothiazide

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.

  • Try to take the daily dose in the morning so its diuretic effects don’t interfere with sleeping.

  • Swallow the tablet or capsule whole.

  • If the tablet can’t be swallowed, it can be crushed, mixed with a small amount of liquid, and taken that way.

  • Store the medicine in a closed container at room temperature.

What to do if you miss a dose of Hydrochlorothiazide

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. 

  • Do not take extra medicine to make up for a missed dose.

Hydrochlorothiazide contraindications

  • This medicine is not right for everyone. 

  • Do not use this medicine if you have had an allergic reaction to hydrochlorothiazide or sulfa drugs.

  • Do not use this drug if you are not able to urinate.

Hydrochlorothiazide warnings

  • Tell any doctor or other healthcare provider who treats you that you are using this medicine.

  • Your doctor will need to perform regular blood tests to monitor the effects of this medicine. Keep all appointments.

  • Tell your doctor if you are pregnant or breastfeeding.

  • Also tell your doctor if you have:

    • Kidney disease

    • Liver disease

    • Electrolyte problems

    • High cholesterol

    • Diabetes

    • Gout

    • Glaucoma

    • Lupus

    • Trouble urinating

  • This medicine may cause the following problems: 

    • Electrolyte imbalance

    • Eye or vision problems, including temporary near-sightedness or rapidly-progressing glaucoma

    • High uric acid in the blood

    • Elevated blood sugar

    • Elevated cholesterol 

    • Increased risk of skin cancer

  • This medicine could lower your blood pressure too much, especially when you first use it or if you are dehydrated. 

  • This medicine may make you dizzy. It can also make you feel faint or lightheaded when changing position or standing up. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

  • This medicine may make your skin more sensitive to sunlight and UV exposure. Consider wearing protective clothing, sunscreen, and sunglasses while using this medicine.

Hydrochlorothiazide interactions

  • To avoid potentially hazardous drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medications, and supplements you use before taking hydrochlorothiazide tablets or capsules.

  • Tell other healthcare providers you are using this medicine before they prescribe new medications.

  • Some medicines can cause problems when combined with hydrochlorothiazide. Tell your doctor if you are also using:

    • Other blood pressure drugs

    • Insulin or diabetes medications

    • Corticosteroids

    • Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen

    • The cholesterol drugs cholestyramine or colestipol

    • Some types of muscle relaxants

    • The heart rhythm drug digoxin

    • The mood stabilizer lithium

  • Alcohol, narcotic pain relievers, or sleeping pills may cause you to feel more lightheaded, dizzy, or faint when used with this medicine. 

  • Tell the doctor if you have any upcoming parathyroid tests. Hydrochlorothiazide can distort the results of a parathyroid test.

Hydrochlorothiazide side effects

Serious side effects

Talk to a doctor if you notice any signs or symptoms of a possible serious side effect, including:

  • Trouble seeing, eye pain, blurred vision, or other vision changes

  • Yellowing of the skin or eyes, abdominal pain, tiredness, clay-colored or light stools

  • Unusual tiredness or weakness

  • Confusion, weakness, and muscle twitching

  • Dry mouth, increased thirst, muscle cramps, nausea or vomiting, uneven heartbeat

  • Lightheadedness, dizziness, or fainting

  • Skin changes like sores, reddish patches, irritated areas, shiny bumps, pink growths, or white, yellow, or waxy scar-like areas on the skin

  • Blistering, peeling, or red skin rash

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Hydrochlorothiazide can cause side effects that don’t have symptoms. The doctor will need to perform regular blood tests to catch these problems. These include:

  • Electrolyte imbalances

  • High blood sugar

  • High cholesterol

  • High uric acid in the blood

Less serious side effects

  • Dizziness

  • Diarrhea

  • Abdominal pain

  • Headache

Find more detailed information about hydrochlorothiazide side effects here.