Quick overview

Hydrochlorothiazide is a thiazide diuretic (sometimes called a water pill). In the United States it is available only by prescription. It may be prescribed alone or together with other blood pressure medicines. If you are looking for how to take it, jump to directions; for safety issues, see warnings and side effects; for costs, check pricing; and for US rules, see legal notes.

What it treats

Primary indication: high blood pressure (hypertension). Lowering blood pressure helps reduce the risk of strokes, heart attacks, and kidney problems.

It is also used to manage edema caused by conditions such as heart failure, liver cirrhosis, and some kidney disorders, or swelling related to certain medicines (for example, corticosteroids or estrogen).

How to take it

Use hydrochlorothiazide exactly as your prescriber instructs. It can be taken with or without food, preferably at the same time each day.

Because it increases urination soon after a dose, many people take it in the morning. If you take it twice daily for edema, your clinician may suggest a second dose in the early afternoon. To avoid sleep disruption, try not to take it after about 6 pm.

If you have questions about your schedule, electrolytes, or combining it with other medicines, ask your pharmacist or clinician. For safety pointers, review precautions.

How it works

Hydrochlorothiazide is a thiazide diuretic that reduces sodium reabsorption in the distal renal tubules, increasing the excretion of sodium, chloride, and water. Over time, this leads to a reduction in blood volume and a lowering of blood pressure.

Dosage forms and strengths

Common US strengths include 12.5 mg and 25 mg tablets. Some manufacturers may offer additional strengths. Your prescriber will choose a dose based on your blood pressure goals, kidney function, and other medicines.

If you miss a dose

Take the missed dose when you remember unless it is close to the time of your next dose. If it is almost time for the next dose, skip the missed dose and take the next dose at the regular time. Do not take two doses at once.

Storage

Keep at controlled room temperature 68 to 77 F (20 to 25 C). Short periods between 59 and 86 F (15 to 30 C) are acceptable. Protect from moisture, heat, and light; do not store in the bathroom. Keep out of reach of children and pets.

Important warnings and precautions

Do not use hydrochlorothiazide if

  • you are taking dofetilide or ketanserin (risk of dangerous heart rhythm changes).
  • you are unable to urinate (anuria).
  • you have had an allergic reaction to hydrochlorothiazide or to other sulfonamide-derived medicines.

General cautions

- Dizziness, lightheadedness, and blurred vision can occur, especially after starting or changing dose. Alcohol, hot weather, fever, or exercise may make this worse. Stand up slowly and know how you react before driving or operating machinery.

- Photosensitivity: you may sunburn more easily. Use sunscreen, protective clothing, and avoid tanning booths until you know your sensitivity.

- Electrolyte changes (low sodium, low potassium, low magnesium) may occur. Your prescriber may recommend a potassium supplement or dietary adjustments. Do not start supplements without medical advice.

- Blood sugar can rise; people with diabetes should monitor more closely and consult their clinician before changing diabetes medicines.

- Gout: hydrochlorothiazide may raise uric acid and trigger gout flares in susceptible individuals.

- Tell your doctor or dentist you use hydrochlorothiazide before any surgery or emergency care.

- Heat exposure and heavy sweating increase the risk of low sodium; discuss plans for vigorous exercise or heat exposure with your clinician.

- Pregnancy and breastfeeding: use only if the potential benefits justify potential risk to the fetus; small amounts appear in breast milk. Discuss with your obstetric provider.

- Lab monitoring: your care team may check blood pressure, kidney function, and electrolytes periodically. Keep all appointments and lab visits.

Possible side effects

Common, usually mild

  • temporary blurred vision
  • nausea or reduced appetite
  • lightheadedness, especially when standing
  • constipation or diarrhea
  • dizziness

Serious, seek medical care promptly

  • confusion or severe drowsiness
  • severe skin reactions such as redness, blistering, or peeling
  • irregular, very fast, or faint heartbeat
  • fainting or seizures
  • yellowing of eyes or skin (possible liver issues)
  • shortness of breath
  • very low urination or dark urine
  • fever, chills, or persistent sore throat
  • muscle cramps, severe weakness, or numbness/tingling
  • unusual bleeding or bruising
  • joint pain, warmth, or redness (including big toe, may signal gout)
  • excessive thirst or very dry mouth
  • vomiting or persistent abdominal pain
  • signs of allergy: rash, hives, itching, swelling of face/lips/tongue, or trouble breathing

Not every side effect is listed here. If symptoms are severe or do not improve, contact your clinician. For general precautions, revisit Important warnings.

Alternatives and similar medicines

Several medicines can serve as alternatives or complements to hydrochlorothiazide for blood pressure or edema. Choice depends on your medical history, kidney function, and treatment goals.

  • Chlorthalidone (thiazide-like diuretic): often longer-acting than hydrochlorothiazide and may lower blood pressure more over 24 hours; may slightly increase risk of low potassium.
  • Indapamide (thiazide-like): long duration and effective for hypertension; sometimes preferred in certain patients.
  • Furosemide (loop diuretic): stronger diuresis; commonly used for edema in heart failure or kidney disease rather than for first-line hypertension.
  • Spironolactone (mineralocorticoid receptor antagonist): useful in resistant hypertension and heart failure; may increase potassium levels and can cause breast tenderness.
  • Combination products: many pair hydrochlorothiazide with other antihypertensives (for example, lisinopril-HCTZ, losartan-HCTZ, valsartan-HCTZ, atenolol-HCTZ) to simplify therapy.
  • Other non-diuretic blood pressure options: ACE inhibitors, ARBs, calcium channel blockers, and beta blockers, which may be used alone or with a diuretic based on your clinician's advice.

Ask your prescriber whether an alternative in this list suits your situation, especially if you experience troublesome side effects or need better 24-hour blood pressure coverage.

Typical US prices (rough estimates)

Prices vary widely by pharmacy, location, dosage, and insurance. The ranges below are approximate out-of-pocket monthly costs for common doses using generic products in the United States:

  • Hydrochlorothiazide 12.5-25 mg daily: about $3 to $15 with common discount programs; $10 to $25 cash price at many pharmacies.
  • Chlorthalidone 12.5-25 mg daily: roughly $8 to $25.
  • Indapamide 1.25-2.5 mg daily: about $15 to $40.
  • Furosemide 20-40 mg daily: around $4 to $15.
  • Spironolactone 25-50 mg daily: typically $6 to $20.
  • Combination tablets with hydrochlorothiazide (for example, losartan-HCTZ): often $10 to $50 depending on product and strength.

Tip: Many US pharmacies honor discount cards or price-match; check reputable price-comparison tools. Insurance copays may be lower than cash prices.

More information and practical tips

- Keep adequate hydration, but avoid excessive fluid intake unless directed by your care team. Sudden weight gain or swelling should be reported.

- Some interactions can be significant, including with lithium (risk of toxicity) and other medicines that affect potassium. Provide your pharmacist with a full medication and supplement list.

- Do not share your prescription with others and do not use someone else's medication. Your dose and monitoring plan are individualized.

If you need a refresher on side effects, return to Possible side effects. For safe use, check Important warnings. For cost comparisons, see Typical US prices.