Minoxidil is the most widely used hair loss medicine in the world and the only one you can buy without a prescription in most countries. For decades that meant a liquid or foam rubbed into the scalp. In the last few years more dermatologists have started prescribing it as a small daily tablet instead. Both forms use the same drug, but they behave differently, and the side effects are not the same either.
A blood pressure pill that grew hair
Minoxidil was first approved in the United States in 1979 as a tablet for severe high blood pressure. Doctors soon noticed that many patients grew extra hair on the face and body. That side effect led to a scalp solution, approved by the FDA for male pattern baldness in 1988 and later for women. Today 2% and 5% liquids and a 5% foam are sold over the counter.
Nobody knows exactly how minoxidil makes hair grow. It widens blood vessels and seems to lengthen the growth phase of the hair cycle and enlarge shrunken follicles. To work, it has to be converted in the follicle by an enzyme called sulfotransferase. People whose scalp has little of this enzyme respond poorly to the topical form, which is one reason some of them do better on tablets.
Topical minoxidil
The usual dose is 1 ml of liquid or half a capful of foam on a dry scalp, twice a day for men. Women are often advised to use the 5% foam once a day. It goes on the thinning area, not on the hair, and needs a few hours to absorb before washing.
- Most common side effects: itching, dryness, flaking and redness of the scalp. The liquid contains propylene glycol, which causes much of the irritation. The foam does not, so it is a good switch for sensitive skin.
- Unwanted hair on the forehead or cheeks, usually from the product running down or from touching the face after applying it.
- Extra shedding in the first two to eight weeks. It looks alarming but usually means old resting hairs are being pushed out to make room for new ones.
Low-dose oral minoxidil
Hair doctors began using very small doses of the tablet, a fraction of what was used for blood pressure, after studies in the 2010s showed good results in women and men. Typical doses are 0.25 to 2.5 mg a day for women and 1.25 to 5 mg for men. The use is off-label, which means the tablet is not officially approved for hair loss and must be prescribed by a doctor.
A 2021 review in the Journal of the American Academy of Dermatology looked at 17 studies with more than 600 patients and concluded that low-dose oral minoxidil was effective and generally well tolerated for several types of hair loss. People like it because it takes a second to swallow, there is no greasy residue and it covers the whole scalp evenly.
Side effects of the tablets
- Extra hair growth on the face, arms or body is the most frequent problem, more noticeable in women. It is dose-dependent and goes away after stopping.
- Fluid retention, such as swollen ankles or a puffy face.
- Faster heartbeat, palpitations, dizziness or headache, especially at the start.
- Rarely, more serious heart problems such as fluid around the heart. This is why doctors ask about heart disease and blood pressure before prescribing and may check them during treatment.
Oral minoxidil is not suitable during pregnancy or breastfeeding, and people with heart conditions, low blood pressure or a pheochromocytoma (a rare adrenal tumor) should not take it.
Which one is better
There is no single answer. Small head-to-head trials suggest the two forms give broadly similar results in pattern hair loss. Topical minoxidil has fewer whole-body effects and you can start it today without seeing a doctor. Tablets are easier to stick to and help people whose scalp reacts badly to the liquid or who do not respond to it.
Whichever form you choose, the rules are the same. Expect to wait three to six months before you see a difference and up to a year for the full effect. Minoxidil only works while you use it. If you stop, the hair it kept or regrew is usually lost again within a few months.
Questions to ask your doctor
- Is my hair loss pattern hair loss, or could it be shedding, alopecia areata or a scalp problem?
- Should I start with foam, liquid or tablets, and at what dose?
- Do I need my blood pressure or heart checked first?
- Would it help to combine minoxidil with another treatment, such as finasteride for men?
Sources
- Randolph M., Tosti A. Oral minoxidil treatment for hair loss, a review of efficacy and safety. Journal of the American Academy of Dermatology, 2021. PubMed
- American Academy of Dermatology, Hair loss diagnosis and treatment. aad.org
- MedlinePlus, Minoxidil topical. medlineplus.gov
