Melatonin and hair loss is a topic attracting growing interest, particularly as more people in the UK are prescribed melatonin for sleep disorders and begin to question its effects on other bodily processes. Melatonin is a prescription-only hormone in the UK, regulated by the MHRA, and is licensed primarily for sleep-related conditions. Whilst research suggests hair follicles contain melatonin receptors, the clinical evidence linking oral melatonin to hair loss or growth remains limited. This article explores what the current science says, which other factors commonly cause hair loss, and when to seek professional advice.

What Is Melatonin and How Is It Used in the UK?

Melatonin is a prescription-only hormone in the UK, licensed for sleep disorders in adults and children via products including Circadin and Slenyto; it is not legally available over the counter without a prescription.

Melatonin is a naturally occurring hormone produced by the pineal gland in the brain, primarily in response to darkness. It plays a central role in regulating the body's circadian rhythm — the internal clock that governs sleep-wake cycles. Endogenous melatonin levels typically rise in the evening, peak during the night, and fall in the early morning hours.

In the UK, melatonin is a prescription-only medicine (POM). The Medicines and Healthcare products Regulatory Agency (MHRA) has approved the following licensed indications:

• Circadin (melatonin 2 mg prolonged-release tablets) — for the short-term treatment of primary insomnia characterised by poor quality of sleep in adults aged 55 years and over

• Slenyto (melatonin prolonged-release tablets) — for sleep disturbances in children and adolescents aged 2–18 years with autism spectrum disorder or Smith-Magenis syndrome, where sleep hygiene measures have been insufficient

• Melatonin 1 mg/mL oral solution (e.g., Colonis) — licensed for the short-term treatment of jet lag in adults

Unlike in some other countries, melatonin supplements are not legally available over the counter in the UK without a prescription. Patients who obtain melatonin through unofficial channels — such as online retailers or from abroad — may be using products that have not been assessed for quality, safety, or efficacy by UK regulators. The MHRA advises caution when purchasing any medicine online from unregistered sources.

Melatonin works by binding to MT1 and MT2 receptors in the brain, helping to shift or reinforce the body's natural sleep timing. It is generally considered to have a mild side-effect profile. Commonly reported effects include daytime drowsiness, headache, and dizziness. Patients should be aware that next-day drowsiness may impair the ability to drive or operate machinery. Melatonin may also interact with certain medicines, including fluvoxamine (which can markedly increase melatonin plasma levels) and other central nervous system depressants. Patients taking other medicines should seek advice from a pharmacist or prescriber before starting melatonin.

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Because of its hormonal nature, there has been growing patient interest in whether melatonin might influence other hormone-dependent processes in the body — including hair growth and hair loss.

If you experience a suspected side effect from melatonin or any other medicine, you can report it via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk.

What the Evidence Says About Melatonin and Hair Growth

Hair follicles contain melatonin receptors, and one small RCT found topical melatonin increased anagen-phase follicles, but evidence is preliminary; oral melatonin prescribed for sleep is not clinically linked to hair loss or growth.

The relationship between melatonin and hair biology is an area of genuine scientific interest, though the evidence base remains limited and should be interpreted with caution. Hair follicles are known to be photoperiod-sensitive structures, and research has demonstrated that melatonin receptors are present in human hair follicles, suggesting the hormone may play a role in regulating the hair growth cycle.

The hair growth cycle consists of three main phases:

• Anagen (active growth phase)

• Catagen (transitional phase)

• Telogen (resting and shedding phase)

Some early-stage studies have explored topical melatonin as a potential intervention for hair loss. A randomised controlled trial by Fischer et al., published in the British Journal of Dermatology (2004), found that a 0.1% topical melatonin solution applied to the scalp was associated with a significantly higher proportion of hair follicles in the anagen phase compared to placebo in women with androgenetic alopecia or diffuse hair loss (n=40). Whilst these findings are of scientific interest, the study was small and further replication in larger, well-designed trials is needed before any clinical recommendations can be made.

It is important to note several key points:

• Topical melatonin formulations studied for hair loss are not licensed for this indication in the UK and are not routinely available on the NHS. They should be considered investigational.

• Oral melatonin taken for sleep is not equivalent to topical melatonin studied for hair loss. There is currently no robust clinical evidence that oral melatonin as prescribed for sleep disorders causes or prevents hair loss in humans.

• A review of the Summary of Product Characteristics (SmPC) for licensed oral melatonin products (Circadin, Slenyto) does not identify alopecia as a recognised adverse reaction, and no regulatory link between oral melatonin use and hair loss has been established.

Some individuals report noticing changes in hair texture or shedding when starting or stopping melatonin, but these observations are largely anecdotal. Patients should be cautious about interpreting preliminary research findings as definitive guidance, and should discuss any concerns with a clinician.

Other Medications and Factors That May Affect Hair Loss

Hair loss is multifactorial; well-established causes include thyroid disorders, iron deficiency anaemia, androgenetic alopecia, and medications such as anticoagulants, retinoids, and chemotherapy agents.

Hair loss — medically termed alopecia — is a multifactorial condition, and it is important not to attribute changes in hair density or shedding to a single cause without proper clinical assessment. A wide range of medications, health conditions, and lifestyle factors are well-established contributors to hair loss.

Medications associated with hair loss include:

• Beta-blockers (e.g., propranolol) — used for heart conditions and anxiety; rarely associated with hair thinning

• Anticoagulants (e.g., warfarin, heparin)

• Retinoids (e.g., isotretinoin for acne)

• Antithyroid drugs (e.g., carbimazole)

• Certain mood stabilisers (e.g., lithium) and, rarely, some antidepressants including SSRIs — though the association with individual agents such as fluoxetine is not well established and should be interpreted cautiously

• Hormonal contraceptives, particularly those with higher androgenic activity

• Chemotherapy agents, which commonly cause anagen effluvium — a diffuse, usually reversible loss of scalp and body hair that occurs because rapidly dividing hair follicle cells are affected by cytotoxic treatment

Beyond medication, several underlying health conditions are strongly associated with hair loss, including:

• Thyroid disorders (both hypothyroidism and hyperthyroidism)

• Iron deficiency anaemia — one of the most common reversible causes, particularly in women

• Polycystic ovary syndrome (PCOS)

• Autoimmune conditions such as alopecia areata or lupus

• Nutritional deficiencies — iron deficiency and low ferritin are the best-evidenced nutritional contributors; associations with zinc or vitamin D deficiency are less well established and should be interpreted with caution

Psychological stress and significant physical illness — including post-viral syndromes such as those seen following COVID-19 — can trigger telogen effluvium, a temporary but distressing form of diffuse hair shedding that typically resolves within several months.

If a patient notices hair loss after starting any new medication, including melatonin, it is worth discussing this with a GP or pharmacist. However, it is equally important to consider the full clinical picture before assuming a causal link, as coincidental timing is common. Suspected drug-related hair loss can be reported via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk.

When to Speak to a GP or Pharmacist About Hair Loss

You should see a GP promptly if you experience sudden, patchy, or scarring hair loss, or hair loss accompanied by systemic symptoms; a pharmacist can review medicines for known hair-loss associations.

Hair loss can be a distressing experience, and whilst it is often benign and self-limiting, there are circumstances in which it warrants prompt medical attention. Knowing when to seek professional advice is an important aspect of patient safety.

You should speak to your GP if you notice:

• Sudden or rapid hair loss over a short period

• Patchy hair loss, particularly in well-defined circular areas (which may suggest alopecia areata)

• Hair loss accompanied by scalp redness, scaling, itching, pain, pustules, or scarring — scarring alopecia requires urgent dermatology referral to prevent permanent hair loss

• Loss of eyebrows or eyelashes alongside scalp hair loss

• Suspected scalp infection, including ringworm (tinea capitis), particularly in children

• Hair thinning alongside other symptoms such as fatigue, weight changes, or feeling unusually cold or warm (which may indicate a thyroid disorder)

• Hair loss following a new prescription medicine, including melatonin

• Significant emotional distress related to hair changes

A pharmacist can also be a valuable first point of contact. They can review your current medicines for known hair-loss associations, advise on whether any over-the-counter products are appropriate, and help determine whether a GP referral is needed.

For patients already taking prescribed melatonin who are concerned about hair changes, it is advisable to discuss any concerns with a clinician before making changes to prescribed treatment, rather than stopping or altering the dose independently. The potential benefit of the medicine must be weighed against any reported side effects in a shared decision-making conversation.

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In most cases, a GP will begin with a focused history and examination, followed by targeted blood tests to rule out common reversible causes. Typical first-line investigations include a full blood count (FBC), serum ferritin, and thyroid-stimulating hormone (TSH). Where female-pattern hair loss or signs of hyperandrogenism are present, androgen levels may also be checked. Early investigation often leads to more effective management.

NHS Guidance on Managing Hair Loss Safely

NHS and NICE guidance supports topical minoxidil and prescription finasteride (in men) as evidence-based treatments for androgenetic alopecia; melatonin has no licensed indication for hair loss in the UK.

The NHS provides clear, accessible guidance on hair loss, recognising it as a condition that can significantly affect quality of life and psychological wellbeing. According to NHS resources, the most common form of hair loss is androgenetic alopecia (male- or female-pattern baldness), which is largely genetic and hormonal in origin. This type of hair loss is gradual and follows a predictable pattern.

For those seeking treatment, NHS and NICE Clinical Knowledge Summaries (CKS) outline several evidence-based options:

• Minoxidil (available over the counter as a topical solution or foam) is licensed for androgenetic alopecia in both men and women and is a well-evidenced option supported by NHS guidance. It is typically used without a prescription and is not routinely provided on the NHS for cosmetic hair loss.

• Finasteride (prescription only, for men) works by inhibiting the conversion of testosterone to dihydrotestosterone (DHT), a key driver of androgenetic alopecia. Important cautions apply: finasteride is contraindicated in women who are pregnant or may become pregnant due to the risk of harm to a male foetus; potential sexual side effects (including reduced libido and erectile dysfunction) should be discussed before starting treatment; and it is not routinely available on the NHS for androgenetic alopecia, with many patients accessing it via private prescription.

• Referral to a dermatologist is recommended for complex, scarring, or rapidly progressive alopecia, or where the diagnosis is uncertain.

The NHS also emphasises the importance of psychological support for those significantly affected by hair loss. Conditions such as alopecia areata can have a profound impact on self-esteem and mental health, and referral to counselling or support groups (such as Alopecia UK) may be appropriate.

Regarding melatonin specifically, there is currently no licensed indication for melatonin in the treatment of hair loss in the UK. Topical melatonin formulations for hair loss are unlicensed and not routinely available on the NHS. Patients should be cautious about purchasing unregulated topical or oral melatonin products online, as these may not meet UK safety standards.

Ultimately, safe management of hair loss begins with an accurate diagnosis. Self-treating without professional guidance — whether with melatonin or any other product — risks delaying the identification of a treatable underlying cause. If you suspect a medicine is causing hair loss, you can report this via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk.

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