Pattern hair loss, explained

How common it is

Pattern hair loss is the most common reason hair gets thinner over the years. Doctors call it androgenetic alopecia. In men, about half are affected by age 50, and about 80% by age 70 and over.¹

It is common in women too, although it looks different and people talk about it less. In two studies of women in the UK and the USA, it affected 3–6% of those under 30, rising to between 3 and 4 in 10 at age 70 and over.¹

So if you are noticing it, you are far from alone. It is not caused by anything you did, such as washing too often or wearing a hat.

What is happening in the follicle

Each hair grows in cycles: a long growing phase, a short changing phase and a resting phase. At the end, the hair falls and the follicle starts a new one. If this is new to you, The hair cycle, explained covers it in a few minutes.

Pattern hair loss changes that cycle. The key player is dihydrotestosterone, or DHT. The body makes it from testosterone with the help of an enzyme called 5-alpha reductase. Everyone has DHT, women included. What differs is how sensitive your follicles are to it, and that sensitivity is largely inherited.

In sensitive follicles, DHT shortens the growing phase. Each time the cycle starts again, the follicle comes back a little smaller. Doctors call this miniaturisation. A smaller follicle makes a thinner, shorter and paler hair. Over many cycles, thick hairs are replaced by fine ones that barely cover the scalp.

Two more things follow. Because hairs grow for less time, a bigger share of them is resting at any moment. And the pause between one hair falling and the next one appearing can get longer, so some follicles sit empty for a while.

This is why pattern hair loss feels different from shedding. You may not see more hair in the drain. Instead, the hair you have covers less, and the scalp shows through under bright light.

The sensitive follicles sit mostly on the top and front of the head. Follicles at the back and sides are usually spared. That is why even advanced pattern loss tends to leave a band of hair around the back and sides.

How it looks in men and in women

Men

In men, the hairline usually moves back at the temples first, which makes an M shape. Thinning often starts at the crown as well. Over years, the two areas can grow and meet.

Doctors describe these stages with the Hamilton–Norwood scale.^2,3 It runs from stage I, with little or no change, to stage VII, where only a band of hair is left at the back and sides. It is a picture scale for describing the pattern. It is not a test, and it does not tell you how fast your own hair will change.

Women

In women, the front hairline usually stays where it is. Instead, hair thins over the top of the head, and the parting slowly gets wider. Many women first notice more scalp under bright light, or a thinner ponytail.

It can begin from the late twenties and is most common after 50.⁴ Doctors use picture scales for women too, such as the Ludwig scale, which grades how far the parting has widened. Like the scale for men, these scales describe what is there. They do not diagnose anything.

Is it pattern loss or something else?

Pattern hair loss is gradual, over months and years. Sudden heavy shedding all over the head is more likely to be telogen effluvium, which often follows an illness, a birth or a hard time. See Shedding after stress, illness or birth.

Round smooth patches, a sore or red scalp, or hair that breaks off point to other causes. A doctor or dermatologist can usually tell these apart by looking closely at your scalp.

If you are a woman with irregular periods, bad acne or extra facial or body hair, mention it. These can be signs of raised male hormones, and that changes which treatments fit.¹

Why starting early matters

Pattern hair loss does not usually stop by itself. In the large finasteride trials, men who took a placebo kept losing hair over two years.⁵

The general understanding in dermatology is that treatments work on follicles that are still alive and producing hair, even if that hair is thin. A treatment can slow the shrinking, and it can sometimes help a miniaturised follicle grow a thicker hair again. A follicle that has stopped making hair altogether, where the scalp has been smooth and shiny for years, is much less likely to respond. No medicine can make new follicles.

The evidence points the same way. The 2017 European guideline recommends minoxidil and finasteride for men at early to middle stages of the Hamilton–Norwood scale, II to V.¹ In the EU, finasteride 1 mg is authorised for men aged 18 to 41 with early-stage pattern hair loss.⁶ We know much less about how well treatments work at later stages.

So the honest message is not "hurry or lose everything". It is this: if you have noticed thinning and it bothers you, look at your options now rather than in a few years. Keeping hair is easier than getting it back.

The main options

These are the treatments people ask about most. The last column sums up, in plain words, how sure the 2017 European guideline and the best reviews let us be. For a side-by-side view on the same measures, see the pattern hair loss comparison.

Minoxidil is recommended for both women and men by the 2017 European guideline.¹ It is sold without a prescription in many European countries, for example Poland and Czechia.^7,8 It can cause scalp itching or irritation, and some extra shedding in the first weeks.^9,1

Finasteride lowers DHT, so it acts on the cause described above. The guideline recommends finasteride 1 mg for men.¹ It needs a prescription, for example in Poland and Ireland.^7,10 In 2025 the European Medicines Agency confirmed suicidal thoughts as a side effect of finasteride tablets, with unknown frequency. Anyone on it who notices mood changes should stop and get medical advice.⁶

Red light devices (low-level laser) shine red light on the scalp. The guideline suggests them as an add-on to other treatment, for both women and men.¹

Microneedling uses a roller or pen with fine needles, usually together with minoxidil. Pooled trials found higher hair counts than with minoxidil alone, but results varied a lot between studies, and mild side effects were more common.¹¹ The guideline says more studies are needed.¹

PRP (platelet-rich plasma) means injecting a concentrate made from your own blood into the scalp, usually at a clinic. A pooled analysis found more hair than with placebo, but the authors rated the evidence as low quality.¹² The guideline makes no recommendation for or against it.¹

Hair transplant moves follicles from the back of the head to thin areas. The guideline says it can be considered when there is enough donor hair.¹

Two rules apply to almost everything here. First, give a treatment about 6 months before you judge it.¹ Second, the effect lasts only while you keep using it. After stopping minoxidil, for example, extra hair loss usually starts about 3 months later.¹

For women: what is different

Our guide to hair loss in women covers shedding after birth, iron, thyroid and PCOS too. Here is the short version for pattern hair loss.

The cause in women is less clear than in men. DHT plays a part for many, but many women with pattern hair loss have normal hormone levels. Some treatments that work in men do not carry over.

Minoxidil is the main treatment. A Cochrane review of trials in women found that those using minoxidil were nearly twice as likely as those on placebo to report moderate or marked regrowth.¹³ The 2% and 5% strengths did about the same.¹³ The guideline recommends 2% solution twice a day or 5% foam once a day.¹

Red light devices have also been tested in women, and the guideline suggests them as an add-on for both sexes.¹

Finasteride is a different story. In the same Cochrane review, finasteride 1 mg did no better than placebo in women, although the evidence was weak.¹³ The guideline suggests not using it after menopause.¹ It must not be used by women who are or could become pregnant.

Spironolactone is a tablet that blocks the effect of male hormones. Some doctors prescribe it for women, but the evidence is early. In a small pilot trial, 48 premenopausal women used minoxidil together with either spironolactone or a placebo for 24 weeks.¹⁴ More women on spironolactone improved moderately or markedly (38% against 9%). But the difference in hair counts was not clear, and over a third had irregular periods.¹⁴

The guideline makes no recommendation for or against spironolactone in women with normal hormone levels, and the Cochrane review lists it among treatments that need more trials.^1,13 It is not used in pregnancy, so a doctor will talk about contraception before you start.

What to do first

• Get it confirmed. A doctor or dermatologist can check that this is pattern hair loss and not another cause. This matters most if your loss is sudden, patchy or comes with other symptoms.
• Take photos. Photograph your hairline, crown or parting in the same light every month or two. It is the fairest way to judge slow change.
• Pick something you can keep doing. Every option here works only while you use it. A treatment you can live with for years beats a stronger one you stop after a month.
• Judge it at 6 months, not 6 weeks. Early shedding on minoxidil is expected, and real change takes time.¹