Hydrochlorothiazide (HCTZ) 12.5 mg / 25 mg / 50 mg Tablets: Prescription Thiazide Diuretic for Hypertension, Oedema, and Fluid Retention — Often Combined with ACE Inhibitors or ARBs

Information last reviewed: May 2026 — for educational purposes only.

What Is Hydrochlorothiazide?

Hydrochlorothiazide — commonly abbreviated HCTZ — is a thiazide diuretic (water pill) that works by inhibiting sodium-chloride co-transport in the kidney's distal convoluted tubule. This reduces sodium and water reabsorption, increasing urine output and lowering blood volume and pressure. HCTZ is frequently prescribed alone or in fixed-dose combinations with ACE inhibitors, ARBs, or beta-blockers for the management of hypertension.

Prescription (Rx) Status

Hydrochlorothiazide is a prescription-only medication in the United States and most countries. It is available as an inexpensive generic tablet. It requires a licensed healthcare provider's evaluation because thiazide therapy can alter serum electrolytes (particularly potassium, sodium, and magnesium), affect blood glucose levels, and is contraindicated in anuria or severe renal impairment.

What Is HCTZ Used For?

Primary uses include: hypertension (high blood pressure), oedema associated with heart failure, hepatic cirrhosis, and corticosteroid/oestrogen therapy, as well as nephrolithiasis (calcium kidney stones — HCTZ paradoxically reduces urinary calcium excretion and is used for stone prevention). It may be combined in pills such as Lisinopril/HCTZ, Losartan/HCTZ, or Bisoprolol/HCTZ.

Tablet Strengths

Hydrochlorothiazide oral tablets are available in: 12.5 mg, 25 mg, and 50 mg. Capsule formulations (12.5 mg) also exist. Typical starting dose for hypertension: 12.5–25 mg once daily in the morning. Maximum dose: 50 mg/day (oedema doses can be higher under specialist supervision).

Price

HCTZ is one of the most affordable prescription medications available. Generic 25 mg tablets cost approximately $4–$10 for a 30-day supply at most major pharmacies, and many discount programs offer it at no charge with qualifying insurance.

Frequently Asked Questions

Q: Does hydrochlorothiazide deplete potassium?
A: Yes. HCTZ can cause hypokalaemia (low potassium). Your doctor may advise potassium-rich foods, a supplement, or a potassium-sparing co-prescription (e.g. triamterene/HCTZ as Dyazide).

Q: When should I take HCTZ?
A: Usually in the morning to avoid nocturia. Take with or without food. Avoid taking in the evening.

Q: Can HCTZ be taken long-term?
A: Yes, for chronic hypertension management, but routine monitoring of electrolytes, kidney function, and glucose is recommended.

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