Bendroflumethiazide

High blood pressure is a long-term condition that affects a significant proportion of adults in the United Kingdom and significantly increases the risk of stroke, heart attack, and kidney disease when left untreated. Bendroflumethiazide tablets are a prescription thiazide diuretic used to treat hypertension and oedema in adults. They work by increasing urine production to reduce excess fluid in the body and lower blood pressure. Bendroflumethiazide has been used in the treatment of hypertension in the UK for many decades and remains in clinical use, though current NICE guidance identifies other diuretic classes and antihypertensive medicines as first-line options for most patients. A prescription can only be issued following a clinical consultation with a registered prescriber.

Bendroflumethiazide tablets are an oral prescription medicine containing bendroflumethiazide as the active ingredient. Bendroflumethiazide belongs to the thiazide diuretic class of medicines. Thiazides are sometimes informally referred to as water tablets. They act on the kidney to increase sodium and water excretion in urine, which reduces fluid volume in the body and lowers blood pressure over time.

Bendroflumethiazide is licensed in the United Kingdom for the treatment of hypertension (high blood pressure) and oedema (fluid retention) associated with conditions including heart failure, kidney disease, and liver cirrhosis. It is available in two strengths: 2.5mg and 5mg tablets. The 2.5mg dose is the standard dose used for hypertension. The 5mg strength is used for oedema, where a greater diuretic effect may be required.

All clinical information on this page is drawn from the current UK Summary of Product Characteristics for bendroflumethiazide tablets.

Note on current prescribing guidance: NICE guideline NG136 on hypertension in adults does not recommend thiazide diuretics as a first-line treatment for most patients with hypertension. Current NICE guidance recommends thiazide-like diuretics such as indapamide or chlortalidone in preference to older thiazides such as bendroflumethiazide, where a diuretic is indicated. Bendroflumethiazide may still be appropriate for some patients, particularly those already established on it or where another clinical reason supports its use. Your prescriber will assess whether it is appropriate for your circumstances.

Bendroflumethiazide works by acting on the distal convoluted tubule of the kidney, where it inhibits the sodium and chloride co-transporter. This transporter is responsible for reabsorbing sodium and chloride from the filtered urine back into the bloodstream. By blocking it, bendroflumethiazide increases the amount of sodium and chloride that remains in the urine. Water follows sodium osmotically, resulting in increased urine output.

Effect on Blood Pressure

The initial reduction in circulating fluid volume lowers blood pressure by reducing the amount of fluid the heart must pump. With continued use, peripheral vascular resistance also decreases, contributing further to the antihypertensive effect. Bendroflumethiazide is taken once daily in the morning and provides a sustained reduction in blood pressure throughout the day. It is used alone or in combination with other antihypertensive medicines as part of a broader blood pressure control strategy.

Effect on Fluid Retention

In oedema, the increased excretion of sodium and water reduces the accumulation of fluid in tissues. This can relieve swelling in the legs and ankles, reduce breathlessness caused by fluid in the lungs, and improve overall fluid balance in conditions such as heart failure or liver disease. The diuretic effect of bendroflumethiazide is milder and more sustained than that of loop diuretics such as furosemide, making it suitable for the management of mild to moderate oedema.

Always take bendroflumethiazide exactly as your prescriber instructs. The information below summarises key points from the current UK SmPC. Read the Patient Information Leaflet supplied with your medicine before starting treatment.

• Take bendroflumethiazide once daily in the morning. Taking it in the morning means the increase in urine production occurs during the day rather than disrupting your sleep.
• Bendroflumethiazide can be taken with or without food.
• Swallow the tablet whole with a glass of water.
• If you miss a dose, take it as soon as you remember on the same day. If you only remember the following day, skip the missed dose and continue with your normal schedule. Do not take two doses on the same day.
• Do not stop taking bendroflumethiazide without speaking to your prescriber first. Stopping a diuretic suddenly may cause fluid to accumulate again and blood pressure to rise.
• Attend all monitoring appointments arranged by your prescriber. Bendroflumethiazide can affect electrolyte levels and kidney function, and these require periodic review during treatment.

Bendroflumethiazide tablets are available in two strengths through this service. The appropriate strength will be determined by your prescriber based on the condition being treated and your clinical response.

Bendroflumethiazide 2.5mg Tablets

The 2.5mg tablet is the standard dose used for the treatment of hypertension in adults. For blood pressure management, bendroflumethiazide 2.5mg once daily produces a clinically effective antihypertensive effect with a relatively low risk of electrolyte disturbance compared to higher doses. Increasing the dose above 2.5mg does not generally provide a meaningfully greater reduction in blood pressure but does increase the risk of side effects such as low potassium. Your prescriber will advise on the appropriate dose for your circumstances.

Bendroflumethiazide 5mg Tablets

The 5mg tablet is used primarily for the treatment of oedema, where a greater diuretic effect is required. For oedema, doses of 5mg to 10mg once daily may be used initially, with the dose adjusted depending on clinical response. For longer-term maintenance, a lower dose or an intermittent dosing schedule may be used. All dosing decisions are made by your prescriber. Do not increase your dose or change your dosing frequency without medical advice.

Like all medicines, bendroflumethiazide can cause side effects, although not everyone experiences them. The information below is based on the current UK SmPC. Refer to the Patient Information Leaflet for the full list.

Common Side Effects (may affect up to 1 in 10 people)

• Increased frequency of urination, particularly in the first few hours after taking the tablet. This is an expected effect of the medicine.
• Low potassium levels (hypokalaemia), which can cause muscle cramps, weakness, tiredness, and an irregular heartbeat. Regular blood tests help to detect and manage this.
• Low sodium levels (hyponatraemia), which may cause fatigue, confusion, headache, or nausea.
• Dizziness or lightheadedness, particularly when standing up quickly (postural hypotension).
• Raised blood uric acid levels, which may trigger or worsen gout in susceptible patients.

Uncommon Side Effects (may affect up to 1 in 100 people)

• Raised blood glucose levels, which may be relevant for patients with or at risk of diabetes.
• Raised blood cholesterol or triglyceride levels with longer-term use.
• Nausea, loss of appetite, or stomach discomfort.
• Skin rash or increased sensitivity to sunlight (photosensitivity).
• Impotence (erectile dysfunction) in male patients.

Serious Side Effects: Seek Urgent Medical Attention

Contact your prescriber or go to your nearest accident and emergency department promptly if you experience any of the following:

• Severe muscle weakness, significant cramps, or an irregular heartbeat, which may indicate a serious drop in potassium levels
• Significant reduction in urine output, which may indicate worsening kidney function
• Signs of severe dehydration such as extreme thirst, very dark urine, dizziness, and confusion
• Signs of a serious allergic reaction such as sudden swelling of the face, lips, tongue, or throat, difficulty breathing, or a severe skin reaction
• Sudden severe joint pain, redness, and swelling, which may indicate a gout attack

Report any suspected side effect to your prescriber or pharmacist or via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Bendroflumethiazide Tablets May Be Suitable If You:

• Are an adult already established on bendroflumethiazide for hypertension or oedema and require a repeat prescription
• Have been assessed by a prescriber as requiring a thiazide diuretic as part of your treatment plan
• Have hypertension or oedema and have been clinically assessed as suitable for this medicine

Bendroflumethiazide Tablets Are Not Suitable If You:

• Have severe kidney impairment or are anuric (producing no urine)
• Have severe liver disease or hepatic encephalopathy
• Have low potassium or low sodium levels that have not been corrected
• Have hypercalcaemia (raised blood calcium levels) or are taking calcium or vitamin D supplements in doses that may raise calcium
• Have gout or a history of gout attacks
• Have Addison's disease (adrenal insufficiency)
• Are pregnant or breastfeeding - thiazide diuretics are not recommended during pregnancy and pass into breast milk
• Have a known allergy or hypersensitivity to bendroflumethiazide, other sulfonamide-derived medicines, or any excipient listed in the SmPC
• Are under 18 years of age (this service is for adults only)

Cautions

Caution is required in patients with diabetes mellitus, as thiazide diuretics can impair glucose tolerance and raise blood glucose levels. Patients with mild to moderate kidney impairment may use bendroflumethiazide with care, but regular monitoring of kidney function and electrolytes is essential. Patients with systemic lupus erythematosus (SLE) should be aware that thiazide diuretics may exacerbate this condition. Elderly patients are at greater risk of electrolyte disturbances and postural hypotension.

Important Drug Interactions

Bendroflumethiazide can interact with a number of commonly prescribed medicines. Tell your prescriber about all medicines you take, including over-the-counter products and herbal supplements. The following interactions are of particular clinical importance:

• ACE inhibitors and angiotensin receptor blockers (ARBs): combining these with bendroflumethiazide can cause a significant fall in blood pressure, particularly with the first dose. This combination is common in hypertension management but should be initiated with care.
• Digoxin: low potassium caused by bendroflumethiazide increases the risk of digoxin toxicity. Electrolyte monitoring is especially important in patients taking both medicines.
• Lithium: bendroflumethiazide can increase lithium levels, raising the risk of lithium toxicity. Close monitoring is required.
• NSAIDs such as ibuprofen: these can reduce the diuretic and antihypertensive effects of bendroflumethiazide and increase the risk of kidney problems. Avoid regular use of NSAIDs while taking bendroflumethiazide.
• Antidiabetic medicines: bendroflumethiazide may raise blood glucose levels, potentially requiring an adjustment to the dose of insulin or oral antidiabetic medicines.
• Corticosteroids: concurrent use may increase potassium loss, heightening the risk of hypokalaemia.

This is not a complete list of interactions. Your prescriber will carry out a full clinical assessment, including a review of your current medicines, before any prescription is considered.

Bendroflumethiazide is a prescription-only medicine. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber determines, based on their individual assessment of your circumstances, that bendroflumethiazide is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review your clinical information. This includes your blood pressure readings or fluid balance history; current medicines; relevant medical conditions, including kidney function, diabetes status, gout history, and electrolyte levels where available. Because bendroflumethiazide requires periodic monitoring, the prescriber will also assess whether adequate monitoring is in place before considering whether to issue a prescription.

Not all consultations will result in a prescription being issued. The prescriber may recommend a different dose, a different medicine, or suggest that a face-to-face appointment with your GP is more appropriate. This process is designed to ensure your safety.

If you are already being managed for hypertension or oedema by your GP or a hospital team, please keep them informed of all medicines you are taking, including any prescribed through online services.

• Store below 25°C.
• Store in the original packaging to protect from light and moisture.
• Keep out of the sight and reach of children.
• Do not use after the expiry date printed on the packaging.
• Do not dispose of medicines via household waste or wastewater. Return unused or out-of-date tablets to your pharmacist for safe disposal.

Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

The table below compares diuretic tablets available at Pharmacy Planet. Diuretics lower blood pressure and reduce fluid retention by increasing urine production. Different classes of diuretic work at different sites in the kidney.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Pharmacy Planet is a GPhC-registered online pharmacy providing prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, responsible prescribing, and accurate patient information. We follow GPhC standards, MHRA guidance, and ASA advertising regulations in all aspects of our service.

Our pharmacy team is available to answer questions about bendroflumethiazide, diuretic therapy, or cardiovascular health more broadly. We are committed to providing clear, honest information to support you in managing your health safely and with confidence.

References

1. Electronic Medicines Compendium (eMC). Bendroflumethiazide 2.5mg and 5mg Tablets — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed August 2026.
2. National Institute for Health and Care Excellence (NICE). Hypertension in adults: diagnosis and management. NICE guideline NG136. https://www.nice.org.uk/guidance/ng136. Accessed August 2026.
3. NHS. Bendroflumethiazide. https://www.nhs.uk/medicines/bendroflumethiazide. Accessed August 2026.
4. Joint Formulary Committee. British National Formulary (BNF). Bendroflumethiazide. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed August 2026.
5. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed August 2026.