Minoxidil for women: what the trials found, how long it takes, and side effects

If your part is getting wider or your crown is thinning, minoxidil is probably the first treatment you will hear about. It is also the one with the most research in women. This guide explains what minoxidil does, what the trials in women measured, how long it takes, why some women notice extra shedding, what happens if you stop, and the side effects to watch for.

What minoxidil is and how it works

Minoxidil is a drug that widens blood vessels ^[7]. Applied to the scalp, it is FDA-approved to treat androgenetic alopecia in women, also called female pattern hair loss ^[8]. A review of women with this condition describes topical minoxidil as the only FDA-approved treatment for it ^[11].

Exactly how it regrows hair is still not fully understood ^[7]. It seems to work through several pathways at once, including widening blood vessels and affecting how long hairs stay in their growth phase ^[8]. Minoxidil is a prodrug: enzymes in the hair follicle, called sulfotransferases, convert it to its active form, minoxidil sulfate ^[8]. People with more of this enzyme activity may respond better ^[8]. That is one reason results vary so much from woman to woman.

Very little of it reaches the rest of the body. About 1.4% of topical minoxidil is absorbed through the skin ^[8].

2% solution vs 5% foam

Two forms are sold over the counter for women in the US. Their FDA Drug Facts labels give different directions ^{[1, 2]}.

Is 5% stronger in practice? The evidence is mixed. A Cochrane review found no clear difference between 2% and 5% in women ^[3]. One 48-week trial found that women on 5% rated their own benefit higher than women on 2%, but 5% also caused more itching, irritation, and unwanted facial hair ^[4]. In a 24-week trial of 113 women, once-daily 5% foam was as effective as twice-daily 2% solution and caused less itching and dandruff ^[5].

What the trials in women found

The strongest summary comes from a Cochrane review of treatments for female pattern hair loss ^[3]. Pooling six trials, it found that 157 of 593 women using minoxidil reported a moderate to marked increase in regrowth, compared with 77 of 555 using a placebo, about twice the rate ^[3]. Across eight trials, total hair count rose by about 13 more hairs per square centimeter with minoxidil than with placebo ^[3]. The reviewers rated most of this evidence as moderate to low quality ^[3].

The 2% solution's label reports results from its own clinical studies, in mostly white women aged 18 to 45 with mild to moderate hair loss, after 8 months of use ^[2]:

Notice two things. Even on minoxidil, moderate regrowth was the less common result, and some women on placebo also reported regrowth ^[2]. MedlinePlus puts it plainly: minoxidil may help about 1 in 4 or 5 women grow hair, and may slow or stop loss in most ^[10].

How long the trials ran

• 48 weeks: 381 women aged 18 to 49 compared 5% solution, 2% solution, and placebo, twice daily ^[4].
• 24 weeks: 113 women compared once-daily 5% foam with twice-daily 2% solution ^[5].
• 52 weeks: 322 women compared once-daily 5% foam with twice-daily 2% solution. Both increased hair counts by about 24 hairs per square centimeter at 24 weeks ^[6].

It is worth knowing who was studied. The 48-week trial enrolled women aged 18 to 49 ^[4], and the 2% label's studies were mostly in women aged 18 to 45 ^[2]. If you are past menopause, ask your clinician how these results apply to you.

Shedding in the first months

Some women notice more hair in the brush or drain after starting minoxidil. In one 24-week trial in women, hair shedding was reported as a side effect by 12.5% of those using 5% foam and 17.5% of those using 2% solution ^[7]. The women's labels do not list shedding, and the reasons for it are not settled in the sources we reviewed.

If shedding worries you, tell your clinician rather than stopping on your own. They can check whether something else, such as illness, a new medicine, or a thyroid or iron problem, is causing it. Learn more in hair thinning after menopause.

What happens if you stop

Minoxidil works only while you use it. Both women's labels say continued use is needed to increase and keep regrowth, or hair loss will begin again ^{[1, 2]}. A review states that stopping leads to shedding within 3 to 4 months and recommends continuing treatment indefinitely ^[7]. MedlinePlus adds that newly grown hair falls out after stopping ^[10].

This is the single most important thing to know before you start: minoxidil is a long-term commitment, not a course of treatment. If cost or routine makes that hard, talk it through with your clinician first.

Side effects and safety

The most common side effect is irritant contact dermatitis, with itching and scaling, and it is less common with 2% than with 5% ^[7]. Some people have a true allergy. A systematic review of 99 patch-tested patients with allergic reactions to minoxidil products found minoxidil itself was the main allergen in 74.7%, and propylene glycol, an ingredient in many solutions, in 17.1% ^[9].

The women's labels tell you to stop and ask a doctor if any of these occur ^{[1, 2]}:

• Chest pain, rapid heartbeat, faintness, or dizziness
• Sudden, unexplained weight gain
• Swelling of the hands or feet
• Scalp irritation or redness
• Unwanted facial hair growth

The labels also say to ask a doctor first if you have heart disease, and they warn minoxidil may be harmful if used when pregnant or breastfeeding ^{[1, 2]}. Some people notice changes in hair color or texture ^[1]. Using more, or more often, will not improve results ^{[1, 2]}.

The over-the-counter labels say not to use them if your hair loss is sudden or patchy, linked to childbirth, of unknown cause, or if your scalp is red, inflamed, infected, irritated, or painful ^{[1, 2]}. These are reasons to see a clinician first.

If minoxidil alone is not enough

Clinicians sometimes use off-label options, including low-dose oral minoxidil and anti-androgens such as spironolactone and finasteride ^[11]. These are less studied in women than topical minoxidil, and there are few randomized trials that include women ^[11]. Read about one of them in topical finasteride for women.

Minoxidil through WarriorBabe Health

WarriorBabe Health offers four prescription scalp sprays, each combining minoxidil with other ingredients. The Minoxidil + Tretinoin Hair Spray contains minoxidil, finasteride, and tretinoin, and is applied once daily at bedtime. The Minoxidil + Biotin Hair Spray contains minoxidil, tretinoin, fluocinolone, biotin, and melatonin. You can see all four on our hair treatments page, and we explain each add-on ingredient in minoxidil combination sprays.

These sprays are compounded by a licensed pharmacy, with the strength set on your prescription. Compounded drugs are not FDA-approved, and the FDA does not review their safety, effectiveness, or quality before they are marketed ^[12]. The trials in this article tested minoxidil on its own, not these combinations. Three of the four sprays contain finasteride, which must not be used during pregnancy.

To see whether a hair treatment might suit you, take the 2-minute quiz. A licensed clinician reviews your answers and health history and decides whether a prescription is appropriate.

This article is for general information. It is not medical advice and does not replace a visit with a licensed clinician who knows your history. Do not start, stop or change a medication without talking to your clinician. If you think you are having a medical emergency, call 911.