Can HCTZ cause hair loss? Hydrochlorothiazide (HCTZ), a thiazide diuretic used primarily in combination antihypertensive products, does list alopecia as a recognised adverse effect in its Summary of Product Characteristics. Whilst the frequency is often recorded as 'not known' in UK product labelling, post-marketing reports and pharmacovigilance data from both the MHRA and EMA confirm it as a possible side effect. Understanding why this occurs, how common it may be, and what steps to take if you notice hair changes whilst taking HCTZ can help you have a more informed conversation with your GP or pharmacist.

Does Hydrochlorothiazide Cause Hair Loss?

Yes, alopecia is recognised as a possible adverse effect of HCTZ in UK product labelling and by the MHRA and EMA, typically presenting as drug-induced telogen effluvium with hair regrowth expected after discontinuation under medical supervision.

Experiencing these side effects? Our pharmacists can help you navigate them →

Hydrochlorothiazide (HCTZ) is a thiazide diuretic used in the UK, most commonly in fixed-dose combination products for hypertension. It is worth noting that, in line with NICE guideline NG136 and the British National Formulary (BNF), thiazide-like diuretics such as indapamide or chlortalidone are generally preferred over HCTZ for hypertension in current UK clinical practice, and loop diuretics are usually first-line for oedema. HCTZ works by inhibiting sodium and chloride reabsorption in the distal convoluted tubule of the kidney, promoting the excretion of water and electrolytes to reduce blood pressure and fluid retention.

Hair loss — medically termed alopecia — has been reported as an adverse effect in the Summary of Product Characteristics (SmPC) for hydrochlorothiazide-containing medicines. For many UK products, the frequency is listed as 'not known' (meaning it cannot be estimated from available post-marketing data), rather than a defined numerical category. The European Medicines Agency (EMA) and the Medicines and Healthcare products Regulatory Agency (MHRA) both recognise alopecia as a possible side effect based on post-marketing reports and pharmacovigilance data.

Hair loss associated with HCTZ is generally considered to represent drug-induced telogen effluvium — a diffuse, non-scarring form of hair shedding rather than permanent hair loss. In most reported cases, hair regrowth occurs after the medication is discontinued or the dose is adjusted, though this should only be done under medical supervision. If you are concerned about hair changes whilst taking HCTZ, speak with your GP before making any changes to your medication.

How Common Is Hair Loss With HCTZ?

The exact prevalence is unknown; UK SmPCs list alopecia with a frequency of 'not known', meaning it has been reported but cannot be reliably estimated from available post-marketing data.

Quantifying the exact prevalence of HCTZ-related hair loss is difficult. Based on post-marketing reports and UK product labelling, alopecia is listed with a frequency of 'not known' in many SmPCs, meaning it has been reported but cannot be reliably estimated from available data. Some product-specific SmPCs may assign a defined frequency category, so it is worth checking the SmPC for the specific product you have been prescribed via the MHRA/EMC database.

Not sure if this is normal? Chat with one of our pharmacists →

Hair loss is frequently under-reported as a drug side effect, as patients may attribute gradual thinning to stress, ageing, or other health conditions rather than connecting it to a medicine they may have been taking for some time. This is a recognised limitation of spontaneous pharmacovigilance reporting, including the MHRA Yellow Card scheme.

Certain factors may increase susceptibility to drug-induced hair loss, including:

• Pre-existing hair or scalp conditions such as androgenetic alopecia

• Nutritional deficiencies, particularly low iron or zinc levels (where clinically confirmed)

• Hormonal imbalances, including thyroid dysfunction

• Concurrent use of other medications known to affect hair growth

A note on biotin: whilst biotin (vitamin B7) deficiency has been associated with hair loss, true deficiency is uncommon in the UK. High-dose biotin supplementation can also interfere with a range of immunoassay-based laboratory tests, including thyroid function tests, and should be disclosed to your clinician and laboratory if you are taking it.

Because HCTZ is often prescribed as part of a combination antihypertensive regimen — for example, alongside ACE inhibitors or angiotensin receptor blockers — it can sometimes be difficult to identify which component, if any, is responsible for hair changes. A thorough medication review with your GP or pharmacist is therefore essential.

Why Some Medicines Affect Hair Growth

Drug-induced hair loss most commonly occurs via telogen effluvium, where a pharmacological stressor prematurely shifts hair follicles into the resting phase, causing diffuse shedding two to four months later.

To understand why HCTZ might contribute to hair loss, it helps to appreciate the normal hair growth cycle. Hair follicles cycle through three phases: anagen (active growth), catagen (transition), and telogen (resting and shedding). At any given time, approximately 85–90% of scalp hairs are in the anagen phase, with the remainder in telogen.

Drug-induced hair loss most commonly occurs via telogen effluvium, where a physiological or pharmacological stressor causes a disproportionate number of follicles to shift prematurely into the telogen phase. This results in diffuse shedding, typically noticed two to four months after the triggering event — which is why patients may not immediately associate hair loss with a medication they started some time ago. This pattern is well described in clinical literature and in guidance from the British Association of Dermatologists (BAD) and NICE CKS.

The precise mechanisms by which HCTZ might trigger telogen effluvium are not fully established. Some hypotheses include effects on electrolyte balance or micronutrient levels, but these remain speculative for HCTZ specifically and are not confirmed by robust clinical evidence. It is important to recognise that causality is often difficult to attribute to a single medicine, particularly when the underlying conditions being treated — such as poorly controlled hypertension — can themselves be associated with hair thinning.

If you are experiencing hair loss whilst taking HCTZ, a structured assessment by your GP is the most reliable way to identify contributing factors.

What to Do If You Notice Hair Thinning on HCTZ

Do not stop HCTZ without medical advice; instead, keep a record of hair changes, review your diet, and consult your GP to investigate potential causes and review your medication.

If you begin to notice increased hair shedding, thinning, or changes in hair texture whilst taking hydrochlorothiazide, the first and most important step is not to stop your medication without medical advice. Abruptly discontinuing an antihypertensive can lead to a rebound rise in blood pressure, which carries its own significant health risks.

Instead, take a measured and methodical approach:

• Keep a record of when you first noticed the hair changes, the pattern of loss (diffuse or patchy), and any other new symptoms

• Review your diet to ensure you are consuming adequate protein, iron, and zinc — nutritional deficiencies are a common and treatable cause of hair loss

• Check for other potential causes, including recent illness, significant stress, hormonal changes (particularly in women around the menopause), or thyroid problems

• Avoid aggressive hair treatments such as bleaching, tight hairstyles, or excessive heat styling, which can worsen fragile hair

If you are considering taking nutritional supplements, discuss this with your GP or pharmacist first rather than starting them unsupervised. Supplementation is most appropriate when a deficiency has been confirmed by a blood test. It is also worth noting that high-dose biotin (vitamin B7) supplements can interfere with thyroid function tests and other immunoassays — always inform your clinician and the laboratory if you are taking biotin before having blood tests.

Bring a complete list of all medicines and supplements to your GP appointment, including any over-the-counter products or herbal remedies, to help ensure a thorough assessment. The NHS Hair loss (alopecia) page also provides useful patient-facing guidance on self-care and when to seek help.

Speaking to Your GP or Pharmacist About Side Effects

Your GP can review your medication, request relevant blood tests including TFTs, FBC, and serum ferritin, and consider a dose adjustment or switch if HCTZ is strongly suspected as the cause.

Your GP or community pharmacist is the most appropriate first point of contact if you suspect HCTZ is contributing to hair loss. In the UK, NICE guidance emphasises shared decision-making in the management of long-term conditions, and discussing side effects openly is an important part of this process.

When you attend your appointment, your GP may:

• Review your current medication regimen to identify any other potential causative agents

• Request blood tests to help rule out common medical causes of hair loss; in line with NICE CKS guidance on telogen effluvium, initial investigations typically include thyroid function tests (TFTs), a full blood count (FBC), and serum ferritin. Further tests — such as vitamin D, vitamin B12, or zinc — may be considered if clinically indicated based on your history and examination

• Refer you to an NHS dermatologist (via GP referral) if the hair loss is significant, patchy, or associated with scalp changes such as redness, scaling, or scarring

• Consider a dose adjustment or medication switch if HCTZ is strongly suspected and an alternative antihypertensive is clinically appropriate

You can also report suspected side effects directly to the MHRA via the Yellow Card scheme (yellowcard.mhra.gov.uk). This voluntary reporting system helps regulators monitor the safety of medicines in real-world use and contributes to ongoing pharmacovigilance.

Seek prompt medical advice if you experience:

• Sudden or rapidly progressive hair loss

• Patchy bald areas rather than diffuse thinning

• Associated scalp pain, itching, or inflammation

• Hair loss alongside other new symptoms such as fatigue, weight changes, or palpitations

These features may indicate an underlying condition requiring investigation beyond a simple medication review.

Alternative Treatments and Next Steps

NICE NG136 recommends indapamide or chlortalidone over HCTZ for hypertension; switching may be considered, and hair regrowth after telogen effluvium typically takes three to six months following removal of the causative factor.

If your GP determines that HCTZ is likely contributing to hair loss and a change in treatment is appropriate, there are several alternative antihypertensive options available. NICE guideline NG136 recommends a stepwise approach to blood pressure management, and thiazide-like diuretics such as indapamide or chlortalidone are preferred over HCTZ in current UK clinical practice, as supported by the BNF, due to their more favourable cardiovascular outcomes data. Switching to one of these alternatives may be considered, though whether this resolves hair loss is based largely on case reports and post-marketing experience rather than robust trial data.

For patients in whom a diuretic remains necessary, your GP may explore whether the lowest effective dose of HCTZ is being used, or whether combination therapy at lower individual doses could achieve the same therapeutic effect with fewer side effects.

In parallel, addressing any confirmed nutritional deficiencies is an important step. If blood tests reveal low ferritin or zinc levels, supplementation under medical guidance may support hair recovery. Hair regrowth following telogen effluvium is typically a slow process — it may take three to six months after the causative factor is removed before noticeable improvement is seen, as described in British Association of Dermatologists (BAD) patient information.

For those experiencing significant or persistent hair loss, a referral to an NHS dermatologist via your GP is the appropriate route. Trichologists are not medically regulated healthcare professionals and are generally accessed privately rather than through the NHS; if you are considering this route, ensure you are aware of this distinction. Treatments such as topical minoxidil are available for certain types of hair loss and can be discussed with a dermatologist. Overall, the outlook for drug-induced telogen effluvium is generally positive, and with appropriate management, most people see meaningful hair recovery in time.

Frequently Asked Questions