Key Takeaways

• There are many reasons for hair loss. But most fit into three categories: genetic, medical, or lifestyle. The most common cause is genetics. Medical hair loss causes include hormonal imbalances, medications, and medical conditions, while lifestyle factors include chronic stress and crash dieting. 
• Hair loss is common, affecting most of us at some point. But it’s not always permanent. Many types of hair loss can recover on their own or with proper treatment. 
• Hair loss is more likely to happen gradually, almost imperceptibly — especially when the cause is related to genetics, hormonal imbalances, or nutritional deficiencies. But it can also strike suddenly, usually when an event like childbirth, a major illness, or extreme stress forces a load of hair follicles into shedding prematurely. 
• Different types of hair loss respond to different treatments, which means getting the right diagnosis is pivotal to addressing the root cause of your hair loss. For example, what works for androgenetic alopecia won’t necessarily help with alopecia areata. 

What Controls Hair Growth?

To understand why hair falls out, it helps to know how it grows in the first place. Your hair doesn’t just grow continuously; it goes through a natural cycle with three main phases: growth, transition, and rest.

First up is the anagen phase: the active growth period. This phase lasts 3–6 years, with about 90% of your hair growing at any given time. It’s also the phase we all want our hair follicles to stay in. But sadly, all good things come to an end. 

Next comes catagen, a transition lasting 2–3 weeks, where growth stagnates. 

Then there’s telogen, the resting phase where hair just hangs out for about 3 months before it eventually sheds to make room for new growth. 

That’s if everything runs smoothly.

But when something disrupts it — whether that’s stress, illness, hormonal changes, or genetics — more hairs can get pushed into that telogen shedding phase. 

The thing is, we all have slightly different cycles based on our genetics, age, and overall health. Some people naturally have longer growth phases, which means thicker, longer hair. Others might be more sensitive to hormones that can shorten these cycles. 

Understanding your hair’s natural rhythm is key to spotting when something’s gone wrong. 

Looking for something else?

• Men’s hair loss treatment
• Women’s hair loss treatment

What Are the Main Causes of Hair Loss?

There are many reasons for hair loss. Genetics is the biggest factor in hair loss, but other causes of hair loss include hormonal changes, medical conditions and treatments, and lifestyle factors, such as smoking or extreme dieting. 

Genetics

Genetics is one of the biggest causes of hair thinning and loss. It’s even got a name: androgenetic alopecia, also known as male pattern baldness and female pattern hair loss. 

An oft-cited 2003 study of twins shows that your genes are about 80% responsible for male pattern baldness. If your dad, mum, or grandparents experienced hair loss, there’s a good chance you will too. 

Hereditary hair loss happens when the anagen phase is shortened and the telogen phase lengthened — usually because of an inherited sensitivity to a hormone called dihydrotestosterone (DHT), which is known to shrink follicles and disrupt the hair growth cycle. 

Common signs of androgenetic alopecia include a receding hairline and balding crown in men, and diffuse thinning and a widening part in women. 

Hormonal changes

We can’t talk about hair loss without acknowledging the essential role hormones play in the process. A rise in DHT or a drop in oestrogen can disrupt your hair follicles and shorten the hair growth cycle, leading to thinning hair.

So naturally, anything that causes hormonal imbalances, including thyroid issues, pregnancy, menopause, and PCOS, can also lead to hair loss. 

Learn more about hormonal hair loss.

Hormonal hair loss can resemble genetic hair loss, with symptoms including a receding hairline and crown thinning for men, and diffuse thinning and a widening part for women. 

Medications and treatments

Various medical treatments can cause hair loss. Take the most obvious example: radiation and chemotherapy. These drugs can cause a type of hair loss called anagen effluvium, in which you experience total or near-total balding. 

Blood thinners, antidepressants, beta-blockers, and even too much vitamin A can also cause hair to thin. Other medications that have hair loss as a side effect include: 

• ACE inhibitors
• Certain antibiotics
• Anti-seizure medications
• Anti-thyroid medications
• Chemotherapy
• Cholesterol-reducing drugs
• Immunosuppressants
• Oral contraceptive pills

Medical conditions

A medical condition, such as a chronic disease, severe illness, fungal infection, or skin disorder, may also be behind your thinning hair. This is because medical conditions can disrupt your hormones, put your body through severe stress, or scar the scalp. 

The medical condition most commonly associated with hair loss is alopecia areata, an autoimmune disease where your immune system attacks your hair follicles, creating circular bald patches. 

Some chronic illnesses, like lupus or diabetes, can also affect hair growth or cause nutritional deficiencies that may trigger hair loss.

Finally, scalp infections, lichen planus, and even severe cases of dandruff have been known to contribute to hair loss. 

Lifestyle factors

What’s happening in your life can affect your hair more than you might think. Chronic stress, crash dieting, smoking, poor nutrition, and over-styling your hair can all trigger hair loss. 

These causes of hair loss are often the easiest to address, but they require some honest reflection about your habits and lifestyle. 

• Stress and hair loss
• Keto hair loss
• Smoking and hair loss
• Malnutrition and hair loss
• Sleep and hair loss

Can Hair Loss Happen Suddenly?

Absolutely, and it can be pretty hair-raising when it does. What causes sudden hair loss is usually different from the gradual thinning most people think of when they hear ‘hair loss’. 

The most common cause of sudden shedding is something called telogen effluvium, which happens when a big number of hair follicles are ‘shocked’ into the resting phase all at once. 

Common triggers include childbirth, major illness, significant weight loss, or extreme stress. 

The hair loss usually starts 2–3 months after the triggering event, which is why people often can’t figure out what caused it. 

The autoimmune condition alopecia areata is another cause of sudden hair loss, but this creates distinct bald patches rather than overall thinning.

The patches can appear overnight, which may understandably freak you out. According to the US National Institute of Arthritis and Musculoskeletal and Skin Diseases, in most cases, the hair typically regrows naturally. 

Another cause of sudden hair loss is traction alopecia from tight hairstyles like braids, ponytails, or extensions. Hair loss typically occurs around the hairline and temples. 

If you’ve recently changed your hairstyle or started wearing your hair in a way that pulls on the follicles, this could be the culprit. 

The key thing to remember about sudden hair loss is that it often recovers on its own, especially if it’s caused by stress or illness. 

But it’s worth seeing a professional if you notice sudden or patchy hair loss, since early intervention can make a big difference to your recovery. 

The Most Common Hair Loss Diagnoses

When you see a specialist about hair loss, they’ll likely diagnose you with androgenetic alopecia, alopecia areata, telogen effluvium, or some kind of scarring alopecia. 

It’s important to get the right diagnosis because each condition responds to different treatments. For example, what works for androgenetic alopecia won’t necessarily help with alopecia areata, or vice versa. 

Androgenetic alopecia

Androgenetic alopecia is by far the most common diagnosis. A 2025 cross-sectional study using the US National Health Institute’s All of Us dataset confirms that androgenetic alopecia affects up to 80% of men and 50% of women by the age of 70. 

In men, androgenetic alopecia is often called male pattern baldness and typically shows up as a receding hairline and thinning crown. 

In women, it’s usually called female pattern hair loss and presents as diffuse thinning across the top of the head while the hairline stays intact. The part may also start to widen.

This type of hair loss is gradual and progressive, meaning it gets worse over time without treatment. 

Alopecia areata

Though rare, this autoimmune condition affects nearly 2% of the general population at some point in their lives, making it the second most common type of non-scarring hair loss after androgenetic alopecia. 

It can occur at any age, creating smooth, round patches of hair loss. In a tiny percentage of people, it can progress to total scalp loss (called alopecia totalis) or complete body hair loss (alopecia universalis). 

The unpredictable nature of this condition makes it particularly challenging to treat. 

Telogen effluvium

Telogen effluvium is temporary hair loss caused by disruption to the hair growth cycle. Acute telogen effluvium comes on suddenly and usually resolves within 6 months. 

Chronic telogen effluvium can persist for months or years and is often related to ongoing stress, nutritional deficiencies, or hormonal imbalances. 

Scarring alopecias

Scarring alopecias — a type of hair loss caused by damage to the scalp hair follicles — are less common but more serious, as they permanently destroy hair follicles. 

These include conditions like lichen planopilaris, central centrifugal cicatricial alopecia, and frontal fibrosing alopecia. Early diagnosis and treatment are essential to prevent further hair loss. 

Treatments that Target the Root Cause

The key to successful hair loss treatment is to match the treatment to the underlying causes of hair loss. There’s no one-size-fits-all solution here, which is why proper diagnosis is so important. 

The Hairy Pill® takes the same approach, providing a personalised treatment tailored to your needs, with a customised blend of medical-grade ingredients to help halt hair loss and stimulate regrowth. Take the quiz to find out if you’re eligible.

Hair Loss Medications

For androgenetic alopecia, minoxidil is often the first line of treatment for both men and women. It’s an over-the-counter hair growth medication that’s usually used as a topical solution and works by increasing blood flow to the hair follicles. 

Finasteride is another option for men. This prescription hair loss medication is an oral treatment and works by blocking the production of DHT — the hormone responsible for shrinking hair follicles. It’s typically considered unsafe for premenopausal women as it can cause congenital disabilities in male babies. 

Learn more about finasteride. 

Hair Growth Supplements

If a nutritional deficiency contributes to your hair loss, targeted supplementation can make a huge difference. 

Iron deficiency is prevalent in women with hair loss, while low levels of vitamin D, B12, or zinc can also play a role. 

If you suspect you may have a deficiency, it’s worth getting a blood test. It can help identify and treat the deficiency — which may lead to noticeable improvement in hair thickness and growth. 

Learn more about hair growth supplements vs medication.

Topical Steroids or Immunotherapy

For autoimmune conditions like alopecia areata, treatments might include topical corticosteroids, immunotherapy, or newer JAK inhibitors. These treatments work by suppressing the immune system’s attack on the hair follicles. 

If you’re diagnosed with an autoimmune disease, you’ll work with your specialist to determine the right treatment plan for your condition. 

Hair Growth Procedures

More advanced options like hair transplants or platelet-rich plasma (PRP) therapy can be effective for the right candidates. 

Hair transplants work best for stable pattern baldness, while PRP involves injecting your own concentrated platelets into the scalp to stimulate hair growth. 

How to Support Healthy Hair and Reduce Loss

While you can’t change your genes, there’s plenty you can do to give your hair the best chance of staying healthy and strong, including improving your nutrition, practising gentle hair care, cleaning your scalp, reducing stress, and getting enough sleep. 

But first, a warning: You might start strong, but it’s normal to lose momentum as time goes on. 

Consistency is key with all these approaches. Hair grows slowly, so it often takes 3–6 months of consistent healthy habits to see improvements. 

Nutrition

Nutrition forms the foundation of healthy hair growth. Just think about it. Your hair follicles are some of the most active cells in your body, so they need a steady supply of nutrients to function properly. 

Protein is essential, since hair is mostly made up of keratin, a protein. Iron, zinc, vitamin D, and B-complex vitamins all play important roles in hair growth, too. 

Learn more about the best vitamins for healthy hair.

Gentle hair care

This is all about preventing unnecessary damage and breakage. Gentle hair care involves avoiding excessive heat styling, harsh chemicals, and aggressive brushing. 

That means cool it (literally!) on the hairdryer, straightener, curling wands, bleaching, and colouring. 

When your hair is wet, it’s particularly vulnerable to damage, so be extra gentle during washing and styling — and wait for it to fully dry before brushing!

Scalp hygiene

Scalp health is often overlooked, yet it’s essential. After all, it’s where your hair follicles live! 

A clean, healthy scalp provides the best environment for hair growth. Gentle cleansing 2–3 days a week is usually enough, helping to remove product buildup and excess oil. 

Meanwhile, gentle scalp massages can improve blood circulation to the scalp. Some people also benefit from gentle exfoliation to remove dead skin cells. 

Managing stress and sleep

Chronic sleep and stress can cause hair loss! Many things are happening behind the scenes that can link severe stress and sleep deprivation to hair loss. 

But a common thread is that these conditions can increase cortisol levels, which can push hair follicles into the resting phase prematurely. 

Naturally, managing your stress and making sure you get enough sleep may help. 

Stress management is about making sure you have systems in place to reduce stress, such as yoga, meditation, deep breathing, or exercise. 

Getting a good night’s sleep is important, too. Aim for 7–8 hours per night, reducing screentime and caffeine intake before bed if you struggle to get to sleep or stay asleep. 

What to Avoid If You’re Experiencing Hair Loss

The list of things that can worsen hair loss or slow down your recovery is quite long, but harsh chemical treatments, tight hair dos, crash dieting, and heavy haircare products are all right up there.

Harsh chemical treatments, such as bleaching, perming, or straightening, can weaken already vulnerable hair. These processes strip the hair shaft of natural protective oils and can cause breakage that may make your hair look thinner. 

Tight ponytails, braids, buns, and hair extensions all put stress on the hair follicles and may cause traction alopecia. Rapunzel, it might be time to let your hair down!

Crashing dieting or skipping meals can trigger telogen effluvium. Your hair follicles need a steady supply of nutrients, and sudden dietary restrictions can shock them into the resting phase. 

Heavy oils, pomade, and products with harsh ingredients can create buildup that clogs follicles, irritates your scalp, and interferes with healthy hair growth. 

You’ll hear many myths about what works and what doesn’t for hair growth, such as the idea that cutting your hair or shaving encourages hair growth. 

Just remember, hair growth happens at the follicle level. That means trimming your hair to make it grow faster or reduce hair loss won’t do a thing. 

When in doubt, it’s best to consult a doctor. 

When to See a Professional

While some hair loss is normal — we all lose 50–100 hairs per day — certain signs warrant professional attention. These include:

• Sudden or patchy hair loss — including distinct bald patches or significant thinning over weeks rather than months
• Scalp irritation, itching, or scaling
• No noticeable improvement after 3–6 months of self-care

So who should you see?

Your GP is a good starting point — they can run blood tests to check for nutritional deficiencies, thyroid problems, or hormonal imbalances. 

A dermatologist specialises in conditions affecting the hair and scalp and can provide more specialised treatments, while trichologists are hair and scalp specialists who can offer detailed analysis and treatment. 

Any of these practitioners may run tests, such as blood work to check iron levels, thyroid function, vitamin D, and hormones. Sometimes, a practitioner may also want to conduct a scalp biopsy or trichoscopy (a magnified scalp exam) to get a definitive diagnosis. 

The most important thing is not to suffer in silence. Hair loss can take a hit to your confidence and wellbeing, and there are more treatments available now than ever before. 

But the sooner you understand what’s causing your hair loss, the sooner you can start doing something about it.