Hydrochlorothiazide
Pronunciation: (hye-droe-klor-oh-THYE-a-zide).
- Generic name
- Hydrochlorothiazide
- Drug class
- Thiazide diuretic (antihypertensive, diuretic)
Availability and supply rules vary by country
Trade names by country: United States · Canada
Australia: · Full directory
What Hydrochlorothiazide is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how Hydrochlorothiazide works
Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubules of the kidney, increasing the excretion of sodium and water along with potassium and hydrogen ions. This leads to decreased plasma volume, reduced cardiac output, and ultimately lower blood pressure. The antihypertensive effect is also partly due to a reduction in peripheral vascular resistance. (1)
What Hydrochlorothiazide is used for
Management of hypertension (high blood pressure), used alone or together with other antihypertensive medicines.
Management of hypertension (high blood pressure), used alone or together with other antihypertensive medicines. (2)
Adjunctive therapy for edema (fluid retention) associated with congestive heart failure, hepatic cirrhosis, corticosteroid or estrogen therapy, or various forms of renal dysfunction (e.g., nephrotic syndrome, acute glomerulonephritis, chronic renal failure).
Adjunctive therapy for edema (fluid retention) associated with congestive heart failure, hepatic cirrhosis, corticosteroid or estrogen therapy, or various forms of renal dysfunction (e.g., nephrotic syndrome, acute glomerulonephritis, chronic renal failure). (2)
Before taking Hydrochlorothiazide
Do not take / not appropriate for
- Anuria, hypersensitivity to hydrochlorothiazide or sulfonamide-derived drugs, severe renal or hepatic impairment. (Contraindication) (2)
Tell your clinician about
(2)How to take Hydrochlorothiazide
- General Instructions: Take hydrochlorothiazide exactly as prescribed, usually once daily in the morning to avoid nighttime urination. Swallow the tablet or capsule whole with water.. Adult Dosing: For hypertension: 12.5–25 mg once daily; for edema: 25–100 mg daily in single or divided doses. Dosing may be adjusted based on response and tolerability.. Pediatric Dosing: Children: 1–2 mg/kg/day (maximum 37.5 mg/day), given in single or divided doses. Always follow pediatric specialist guidance.. Administration: Take with or without food. Take at the same time each day. If you are prescribed more than one dose, take the last dose no later than mid-afternoon to reduce nighttime urination.. When To Stop: Do not stop taking hydrochlorothiazide without consulting your doctor, even if you feel well. Stopping suddenly may worsen your condition.. Storage: Store at room temperature (68–77°F or 20–25°C), away from moisture, heat, and light. Keep out of reach of children.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2)
Missed dose
If you miss a dose of hydrochlorothiazide, contact your prescriber or pharmacist for guidance on how to proceed, since the right approach can depend on how much time has passed and your individual health situation. Do not take an extra dose to make up for the one you missed without first checking with a healthcare professional.
Overdose
Symptoms of overdose may include severe dehydration, electrolyte imbalance, confusion, muscle weakness, or fainting. Seek emergency medical attention or call your local poison control center immediately. (2)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Weakness, dizziness, or low blood pressure (hypotension), especially on standing up
Incidence: Common
Electrolyte imbalance (low potassium, low sodium, low chloride)
Incidence: Common
Gastrointestinal upset (nausea, vomiting, diarrhea)
Incidence: Common
Raised blood sugar (hyperglycemia) or raised uric acid (hyperuricemia), which may trigger a gout flare
Incidence: Uncommon
Increased sensitivity to sunlight (photosensitivity reaction)
Incidence: Uncommon
Rare blood-count effects such as aplastic anemia or low platelets (thrombocytopenia) — unusual bleeding/bruising, infections, or persistent fatigue should be reported promptly
Incidence: Rare
Eye pain or sudden blurred/decreased vision, which can signal acute myopia or acute angle-closure glaucoma
Incidence: Rare
Serious warnings
May cause significant changes in electrolyte levels (potassium, sodium, magnesium) — serious
Symptoms: May cause significant changes in electrolyte levels (potassium, sodium, magnesium). Use with caution in patients with diabetes, gout, or kidney/liver disease. Can increase sensitivity to sunlight—use sunscreen and protective clothing. May worsen or unmask existing diabetes or gout. Monitor for signs of allergic reactions, especially if you have a sulfa allergy.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Contraindications recorded in the clinician database — serious
Symptoms: Contraindications recorded in the clinician database: Contraindications: Anuria, hypersensitivity to hydrochlorothiazide or sulfonamide-derived drugs, severe renal or hepatic impairment. Precautions: Use with caution in patients with diabetes, gout, electrolyte imbalances, renal or hepatic dysfunction, or a history of hypersensitivity reactions.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Hydrochlorothiazide can cause acute transient myopia and acute angle-closure glaucoma, with symptoms typically starting within hours to weeks of starting the medicine — serious
Symptoms: Hydrochlorothiazide can cause acute transient myopia and acute angle-closure glaucoma, with symptoms typically starting within hours to weeks of starting the medicine; untreated angle-closure glaucoma can cause permanent vision loss. Seek prompt medical attention for eye pain or sudden vision changes after starting this medicine.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Long-term, cumulative use of hydrochlorothiazide has been associated with an increased risk of non-melanoma skin cancer — serious
Symptoms: Long-term, cumulative use of hydrochlorothiazide has been associated with an increased risk of non-melanoma skin cancer. Minimize unnecessary sun/UV exposure and use sun protection while taking this medicine; discuss any new or changing skin lesions with a clinician promptly.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Hydrochlorothiazide may interact with other blood pressure medications, lithium, digoxin, corticosteroids, antidiabetic drugs, NSAIDs, and certain supplements. These interactions can increase the risk of side effects or reduce effectiveness. Always inform your healthcare provider about all medicines and supplements you are taking. | (1) |
| Lithium | Reduced renal clearance of lithium increases the risk of lithium toxicity; lithium generally should not be given together with diuretics like hydrochlorothiazide unless closely monitored by a clinician. | (2) |
| Cholestyramine or colestipol (cholesterol-binding resins) | Can reduce absorption of hydrochlorothiazide by up to 85% (cholestyramine) or 43% (colestipol); these medicines should be taken several hours apart from hydrochlorothiazide, on a clinician's or pharmacist's advice. | (2) |
| NSAIDs (e.g., ibuprofen, naproxen) | May reduce the diuretic and antihypertensive effect of hydrochlorothiazide. | (2) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Historic FDA Pregnancy Category B. Animal studies at high doses showed no evidence of fetal harm, but there are no adequate, well-controlled studies in pregnant women. Hydrochlorothiazide should be used during pregnancy only if clearly needed; it crosses the placenta and has been associated with fetal or neonatal jaundice, low platelets (thrombocytopenia), and electrolyte disturbances. Routine use of diuretics during pregnancy is not recommended. Anyone who is pregnant or planning pregnancy should discuss risks and alternatives with their clinician. (2)
Breastfeeding
Thiazides such as hydrochlorothiazide pass into breast milk. A breastfeeding parent and their clinician should weigh the expected benefit of treatment against the potential risk to the infant before continuing this medicine while nursing. (2)
Children
The usual pediatric dose is 0.5-1 mg per pound (1-2 mg/kg) per day, given as a single dose or in two divided doses, under pediatric specialist guidance. The label caps this at a maximum of 37.5 mg/day for infants under 2 years old, and a maximum of 100 mg/day for children aged 2-12 years. (2)
Renal_impairment
Renal impairment: contraindicated in anuria (absence of urine production); use with caution in other renal disease, as thiazides may precipitate azotemia and cumulative drug effects can develop with impaired kidney function. Hepatic impairment: use with caution, since fluid and electrolyte imbalance caused by this medicine may precipitate hepatic coma in patients with liver disease; severe hepatic impairment is a contraindication recorded in the clinician database. (2)
Hepatic_impairment
Renal impairment: contraindicated in anuria (absence of urine production); use with caution in other renal disease, as thiazides may precipitate azotemia and cumulative drug effects can develop with impaired kidney function. Hepatic impairment: use with caution, since fluid and electrolyte imbalance caused by this medicine may precipitate hepatic coma in patients with liver disease; severe hepatic impairment is a contraindication recorded in the clinician database. (2)
Monitoring
(2)Storage
Store at 20-25 degC (68-77 degF) — USP Controlled Room Temperature — away from moisture, heat, and light, in a well-closed, child-resistant container, out of reach of children.
Study the drug class: Thiazide and thiazide-like diuretics
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Hypertension and edema (see uses)
Dose summary: Edema: 25-100 mg/day as a single or divided dose. Hypertension: initial 25 mg once daily, may be increased to 50 mg once daily; doses above 50 mg are often associated with marked reductions in serum potassium.
Renal context: Contraindicated in anuria. Use with caution in other renal impairment: thiazides may precipitate azotemia, and drug effects can accumulate with reduced kidney function. (1) (2)
Frequently asked questions
How long does it take for hydrochlorothiazide to start working?
Hydrochlorothiazide usually begins to lower blood pressure within 2 hours, with peak effects seen in about 4–6 hours. Its diuretic effect may be noticed within hours of the first dose.
Can I take hydrochlorothiazide if I have diabetes?
Hydrochlorothiazide can be used in people with diabetes, but it may increase blood sugar levels. Regular monitoring of blood glucose is recommended, and your doctor may adjust your diabetes medications as needed.
What foods should I avoid while taking hydrochlorothiazide?
Avoid foods high in sodium and licorice, as these can reduce the effectiveness of the medication. Your doctor may also advise you to monitor potassium intake, depending on your blood test results.
Is it safe to use hydrochlorothiazide during pregnancy?
Hydrochlorothiazide is generally not recommended during pregnancy unless clearly needed, as it may affect fetal development. Discuss risks and benefits with your doctor.
Can hydrochlorothiazide cause dehydration?
Yes, hydrochlorothiazide increases urine output and can lead to dehydration, especially if you do not drink enough fluids or during hot weather. Watch for signs such as dry mouth, extreme thirst, or confusion.
What should I do if I develop muscle cramps or weakness?
Muscle cramps or weakness may be a sign of low potassium or other electrolyte imbalances. Contact your healthcare provider promptly for evaluation and possible blood tests.
Can I drink alcohol while taking hydrochlorothiazide?
Alcohol can increase the risk of low blood pressure and dizziness. It is best to limit or avoid alcohol while taking hydrochlorothiazide.
What happens if I take too much Hydrochlorothiazide?
Taking too much Hydrochlorothiazide can lead to severe dehydration, electrolyte imbalances (like low potassium), dizziness, weakness, and confusion. In extreme cases, it may cause dangerously low blood pressure or kidney problems. If you suspect an overdose, seek immediate emergency medical attention or contact poison control. Do not attempt to self-treat.
Is Hydrochlorothiazide safe during pregnancy?
Hydrochlorothiazide carries a historic FDA Pregnancy Category B classification. Animal studies at high doses did not show fetal harm, but there are no adequate, well-controlled studies in pregnant women, and the drug crosses the placenta — it has been associated with fetal or neonatal jaundice, low platelets, and electrolyte disturbances. Routine diuretic use in pregnancy is not recommended. It is important to consult your doctor to discuss the risks, benefits, and alternative treatments if you are pregnant or planning to become pregnant.
What is the mechanism of action of Hydrochlorothiazide?
Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubules of the kidney, increasing the excretion of sodium and water along with potassium and hydrogen ions. This leads to decreased plasma volume, reduced cardiac output, and ultimately lower blood pressure. The antihypertensive effect is also partly due to a reduction in peripheral vascular resistance. (1)
What is the generic name of Hydrochlorothiazide?
The generic name is Hydrochlorothiazide.
What class of drug is Hydrochlorothiazide?
Hydrochlorothiazide is classed as: Thiazide diuretic (antihypertensive, diuretic).
References
- Hydrochlorothiazide – clinician-authored medicine recordMedGuideGlobal clinician-authored medicine record · Global (internal database) · accessed 2026-08-06 · source 1
- Hydrochlorothiazide Tablet – full prescribing informationU.S. Food and Drug Administration (DailyMed) · United States · accessed 2026-08-06 · source 2
- Hydrochlorothiazide Pregnancy Category BDrugs.com (secondary confirmation) · United States · accessed 2026-08-06 · source 3
- LOSARTAN POTASSIUM AND HYDROCHLOROTHIAZIDE TABLET, FILM COATED [REMEDYREPACK INC.] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 4
- Hydrochlorothiazide — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 5
- Lisinopril and Hydrochlorothiazide — FDA approval record (Drugs@FDA ANDA076230)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 6
- Hydrochlorothiazide — RxNorm normalized drug concept (RXCUI 5487)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 7
Brand names by country
Single-ingredient Hydrochlorothiazide names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- INZIRQO10 mg/mL · ani pharmaceuticals, inc.
Canada
- UROZIDE
- APO-HYDRO