Minoxidil for hair loss: how it works and when to use it

What is minoxidil?

Interestingly, minoxidil did not start out as a hair treatment.

It was originally developed as a vasodilator medication to treat high blood pressure. During its use, a striking side effect was observed: some patients developed increased hair growth.

This observation later led to the development of topical minoxidil for the treatment of androgenetic alopecia.

Decades later, it remains one of the cornerstone medications in the treatment of certain types of hair loss. Topical formulations have extensive clinical experience behind them; moreover, in recent years the dermatological use of low-dose oral minoxidil has expanded, although for alopecia this oral use is off-label and requires medical selection and follow-up.

How does minoxidil act on hair?

There is something important to understand here: minoxidil does not create new hair follicles.

It acts on follicles that still exist.

Its hair-related mechanism is complex and cannot be explained simply by saying it 'brings more blood to the scalp'. Among its effects is the modification of the hair follicle cycle, promoting the maintenance of hair in, or its entry into, the growth phase.

This is why it can progressively improve hair growth, diameter, and density in appropriately selected patients.

But if a follicle has been permanently destroyed, as can occur in certain advanced scarring alopecias, minoxidil cannot rebuild it.

For what type of hair loss does it work best?

One of its main indications is androgenetic alopecia, in both men and women.

This is the progressive loss of density that typically appears in a characteristic pattern, in which genetic predisposition and the hormonal sensitivity of the follicle play a role.

In these patients, minoxidil can help maintain and improve hair density.

But this does not mean that every treatment for hair loss should include minoxidil.

A person may be losing hair due to telogen effluvium, alopecia areata, cicatricial alopecia, a scalp condition, certain medications, endocrine disorders, or nutritional deficiencies, among other causes.

And each situation requires a different approach.

Topical minoxidil: the classic form

Topical minoxidil is applied directly to the scalp and remains one of the classic forms of treatment for androgenetic alopecia.

There are different concentrations and formulations.

One of its drawbacks is precisely the consistency it requires: treatment must be applied regularly for months, and some people find it difficult to maintain over the long term.

It can also cause irritation, flaking, or scalp dermatitis in certain patients.

That is why the choice of formulation and regimen must be individualized.

What about oral minoxidil?

This is probably the aspect that generates the most questions at the moment.

In dermatology, low-dose oral minoxidil is increasingly being used for certain patients with hair loss.

However, there is an important difference that patients should be aware of: oral minoxidil used to treat alopecia is prescribed outside its official indication for hair loss (off-label). An international consensus published in JAMA Dermatology established recommendations on patient selection, contraindications, precautions, and follow-up precisely because its dermatological use has become widespread while large studies and very long-term safety data are still lacking.

In Spain, moreover, its use has become very well integrated into the practice of physicians specialized in trichology, although this does not change its off-label regulatory status for alopecia.

Is oral minoxidil better than topical?

We cannot simply say that one is 'better' than the other.

A review and meta-analysis of clinical trials comparing oral and topical minoxidil in androgenetic alopecia found no significant differences in improvement in hair density or diameter between the two routes. Hypertrichosis was more frequent with oral treatment.

The decision therefore depends on the diagnosis, the patient's characteristics, tolerance, preferences, associated treatments and possible risks.

When do results start to become visible?

Hair has slow biological cycles.

That is why minoxidil does not produce immediate results.

Changes must be assessed over months, not days or a few weeks. Photographs taken under comparable conditions and, where indicated, trichoscopy allow progress to be evaluated in a far more objective way.

Furthermore, during the early phases of treatment some patients may temporarily notice increased hair loss.

This can be alarming, but it does not necessarily mean that the treatment is worsening the alopecia. Modification of the follicular cycle can trigger an initial shedding of certain hairs.

What happens if I stop taking minoxidil?

This is another fundamental question.

When we use minoxidil to maintain hair in a chronic condition such as androgenetic alopecia, its effect generally depends on continuing the treatment.

If it is discontinued, the benefits obtained can be progressively lost and the natural alopecia process manifests itself again.

That is why, before starting, I explain to the patient that we should not approach it as a 'three-month cure'.

In many patients, we are talking about a long-term maintenance strategy.

What are the side effects?

They depend fundamentally on the route used.

With topical minoxidil, irritation, itching, flaking, or scalp dermatitis may appear.

With oral minoxidil, one of the most common adverse effects is hypertrichosis — that is, an increase in body or facial hair. Cardiovascular effects such as dizziness, a drop in blood pressure, tachycardia, or fluid retention may also appear in certain patients, which is why the clinical history and possible contraindications must be assessed before prescribing it.

This is especially important because 'low dose' does not mean 'risk-free medication'.

Can it be used for hair loss in women?

Yes. Minoxidil can be used in certain cases of hair loss in women, especially in female androgenetic alopecia.

But again, we must avoid automatic treatment.

A woman who comes in complaining of hair loss may have androgenetic alopecia, telogen effluvium, thyroid disorders, iron deficiency, or other dermatological or systemic problems.

Several causes can even coexist.

That is why, before starting a prolonged treatment, it is worth determining what we are actually treating.

So, minoxidil — yes or no?

The right answer does not depend on how much hair we find in the shower.

It depends on the diagnosis.

When a patient comes to the consultation saying: 'Doctor, my hair is falling out. Should I use minoxidil?', my answer is: 'First, let's find out why it's falling out.'

Because minoxidil can be an excellent tool, but it does not replace a diagnosis.

A dermatological examination and, when indicated, trichoscopy make it possible to determine what is happening at the follicle and to decide whether minoxidil makes sense, which route of administration may be appropriate, or whether we need an entirely different treatment.

That is the true starting point for any hair loss treatment.