Hydrochlorothiazide 12.5mg Tablets (HCTZ) | Order Online

Hydrochlorothiazide 12.5mg Tablets, commonly abbreviated as HCTZ 12.5mg, are a prescription thiazide diuretic used primarily in the treatment of hypertension (high blood pressure) and oedema (fluid retention) associated with certain medical conditions. Hydrochlorothiazide is one of the most widely prescribed diuretics in the world and is available in multiple strengths, with HCTZ 12.5mg representing the lowest commonly available oral dose. Generic hydrochlorothiazide 12.5mg tablets are marketed internationally across the USA, UK, Australia, UAE, Germany, France, Russia, South Korea and worldwide under multiple brand and generic names.

Product Information

What Is Hydrochlorothiazide 12.5mg Used For?

Hydrochlorothiazide 12.5mg (HCTZ 12.5mg) is prescribed for the following conditions depending on market-specific approved labeling:

Hypertension (High Blood Pressure)
HCTZ 12.5mg is widely used as a first-line or adjunct antihypertensive agent, either as monotherapy or in combination with other blood pressure medicines such as ACE inhibitors, angiotensin receptor blockers (ARBs), beta-blockers or calcium channel blockers. The 12.5mg dose is frequently used to initiate thiazide diuretic therapy, particularly in patients who may be sensitive to higher doses.

Oedema (Fluid Retention)
Hydrochlorothiazide is indicated for oedema associated with congestive heart failure, hepatic cirrhosis and renal dysfunction, including nephrotic syndrome, where approved by local labeling.

United States: HCTZ is indicated for hypertension and oedema. The 12.5mg dose is available as capsules and tablets from multiple generic manufacturers and is commonly used in combination antihypertensive products.

United Kingdom / EU: Hydrochlorothiazide is indicated for hypertension and oedema. The 12.5mg strength is available both as a standalone product and as a component of fixed-dose combination medicines (e.g. with losartan, valsartan, irbesartan, olmesartan or lisinopril).

Australia: Hydrochlorothiazide 12.5mg Australia products are listed on the Australian Register of Therapeutic Goods (ARTG). PBS subsidisation depends on the specific indication, product and patient eligibility.

UAE / Gulf: Hydrochlorothiazide products are registered with the UAE Ministry of Health. Availability of the specific 12.5mg strength varies by registered product and emirate. Consult a UAE-licensed physician or pharmacist.

Germany: Hydrochlorothiazid 12,5mg is available in Germany as standalone tablets and as a component of fixed-dose antihypertensive combinations. All products are prescription-only (rezeptpflichtig).

France: Hydrochlorothiazide 12,5mg is available in France as standalone and fixed-dose combination products, subject to prescription and reimbursement rules.

Russia: Гидрохлоротиазид 12,5 мг is available in Russia under multiple brand and generic names, all requiring a valid prescription.

South Korea: 히드로클로로티아지드 12.5mg is registered for prescription use in South Korea per MFDS-approved labeling.

Always follow the prescribing information for your country and the guidance of your licensed healthcare professional.

How Hydrochlorothiazide 12.5mg Works

Hydrochlorothiazide is a thiazide diuretic that acts on the distal convoluted tubule of the kidney. It works by inhibiting the sodium-chloride symporter (NCC), reducing reabsorption of sodium and chloride ions. This increases urinary excretion of sodium, chloride and water, reducing blood volume and — as a consequence — lowering blood pressure.

Secondary effects of HCTZ include increased excretion of potassium and magnesium and reduced excretion of calcium. These electrolyte effects underlie several of the most important safety considerations with hydrochlorothiazide therapy.

At the 12.5mg dose, hydrochlorothiazide delivers antihypertensive efficacy with a reduced risk of electrolyte disturbance compared to the 25mg and 50mg doses, making it a preferred starting dose in many clinical guidelines.

HCTZ 12.5mg vs 25mg — What Is the Difference?

Both strengths contain hydrochlorothiazide as the active ingredient. The key differences are:

• 12.5mg is the lower starting dose, associated with a reduced risk of hypokalaemia (low potassium) and metabolic disturbance while still delivering meaningful antihypertensive effect
• 25mg provides a greater diuretic and antihypertensive effect but carries a higher risk of electrolyte imbalance
• Most current hypertension guidelines recommend starting at the lowest effective dose, making HCTZ 12.5mg the preferred initiation dose in many patients
• Dose titration to 25mg may be considered if blood pressure control is inadequate at 12.5mg

Do not change your hydrochlorothiazide dose without guidance from your prescriber.

Hydrochlorothiazide 12.5mg in Combination Products

HCTZ 12.5mg is a common component of many fixed-dose combination antihypertensive tablets. Widely available combinations include:

• Losartan / HCTZ 12.5mg — ARB + thiazide combination
• Valsartan / HCTZ 12.5mg — ARB + thiazide combination
• Irbesartan / HCTZ 12.5mg — ARB + thiazide combination
• Olmesartan / HCTZ 12.5mg — ARB + thiazide combination
• Lisinopril / HCTZ 12.5mg — ACE inhibitor + thiazide combination
• Telmisartan / HCTZ 12.5mg — ARB + thiazide combination
• Candesartan / HCTZ 12.5mg — ARB + thiazide combination

Combination products allow patients to achieve blood pressure targets with fewer tablets. Availability of specific combinations varies by country.

Key Safety Information — HCTZ 12.5mg

Electrolyte Monitoring
Hydrochlorothiazide affects electrolyte balance. The most important monitoring parameters are:

• Serum potassium — HCTZ can cause hypokalaemia (low potassium), increasing the risk of cardiac arrhythmias, particularly in patients also taking digoxin
• Serum sodium — hyponatraemia (low sodium) can occur, particularly in elderly patients
• Serum magnesium — HCTZ increases urinary magnesium excretion
• Serum calcium — HCTZ reduces urinary calcium excretion; hypercalcaemia has been reported

Contraindications
Hydrochlorothiazide 12.5mg must not be used in patients with:

• Anuria (absence of urine production)
• Severe renal impairment (creatinine clearance below threshold specified in local prescribing information)
• Severe hepatic impairment
• Refractory hypokalaemia or hyponatraemia
• Hypercalcaemia
• Known hypersensitivity to hydrochlorothiazide, other sulfonamide-derived medicines or any excipient

Important Drug Interactions
Significant interactions include:

• Digoxin — hypokalaemia increases digoxin toxicity risk
• Lithium — HCTZ reduces lithium excretion, increasing lithium toxicity risk
• NSAIDs — may reduce antihypertensive effect of HCTZ
• ACE inhibitors — combination increases risk of first-dose hypotension
• Antidiabetic medicines — HCTZ can impair glucose tolerance
• Corticosteroids — additive potassium loss

Metabolic Effects
HCTZ can affect glucose metabolism (risk of new-onset diabetes with long-term use), uric acid levels (risk of gout), and lipid profiles. These effects are dose-dependent and are less pronounced at the 12.5mg dose.

Sun Sensitivity
Hydrochlorothiazide has been associated with an increased risk of non-melanoma skin cancer with long-term use, and photosensitivity reactions. Patients should use appropriate sun protection during treatment.

Always read the patient information leaflet (PIL) and prescribing information applicable to your country before taking hydrochlorothiazide.

Hydrochlorothiazide 12.5mg — Availability by Country

Frequently Asked Questions — Hydrochlorothiazide 12.5mg

What is Hydrochlorothiazide 12.5mg used for?
Hydrochlorothiazide 12.5mg (HCTZ 12.5mg) is used to treat hypertension and oedema. It is a thiazide diuretic that reduces blood pressure by lowering blood volume through increased urinary sodium and water excretion.

What is HCTZ 12.5mg?
HCTZ is the abbreviation for hydrochlorothiazide. HCTZ 12.5mg refers to a tablet or capsule containing 12.5mg of hydrochlorothiazide — the lowest commonly prescribed oral dose of this thiazide diuretic.

Is Hydrochlorothiazide 12.5mg a water pill?
Yes. Hydrochlorothiazide is a thiazide diuretic, commonly referred to as a water pill, because it increases urine production to reduce fluid retention and lower blood pressure.

What is the difference between HCTZ 12.5mg and 25mg?
Both contain hydrochlorothiazide. The 12.5mg dose is the lower starting dose with a reduced risk of electrolyte disturbance. The 25mg dose provides greater diuretic effect but increases the risk of low potassium and other electrolyte changes. Most guidelines recommend starting at 12.5mg.

Does Hydrochlorothiazide 12.5mg lower blood pressure?
Yes. HCTZ 12.5mg reduces blood pressure by decreasing blood volume through increased urinary excretion of sodium and water. It is used alone or in combination with other antihypertensive medicines.

Can Hydrochlorothiazide 12.5mg cause low potassium?
Yes. HCTZ can cause hypokalaemia (low potassium). The risk is lower at the 12.5mg dose compared to higher doses, but potassium monitoring is still recommended, particularly in patients also taking digoxin or other medicines affected by potassium levels.

Is Hydrochlorothiazide 12.5mg available in Australia?
Yes. Hydrochlorothiazide 12.5mg products are registered on the ARTG. PBS subsidisation depends on indication and eligibility. Consult your prescriber or pharmacist.

Is Hydrochlorothiazide 12.5mg available in the UAE?
Hydrochlorothiazide products are registered in the UAE. Availability of the specific 12.5mg strength depends on the registered product. Consult a UAE-licensed pharmacist or physician.

Can I buy Hydrochlorothiazide 12.5mg online?
Hydrochlorothiazide 12.5mg is a prescription-only medicine in the USA, UK, Australia, UAE and most markets worldwide. A valid prescription from a licensed prescriber is required.

What medicines contain HCTZ 12.5mg?
HCTZ 12.5mg is available as a standalone tablet and as a component of fixed-dose combination medicines including losartan/HCTZ, valsartan/HCTZ, lisinopril/HCTZ, irbesartan/HCTZ and others.

Medical Disclaimer

This information is provided for educational and commercial reference purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Hydrochlorothiazide 12.5mg is a prescription cardiovascular medicine with important electrolyte, renal, metabolic and drug-interaction considerations. Always use it according to the applicable prescribing information and the advice of a qualified healthcare professional licensed in your country.

Last Updated: September 25, 2026