Minoxidil reaches hair in two ways. It is applied to the scalp as a solution or a foam, or it is taken by mouth as a low-dose tablet. The unwanted effects recorded for the two routes are different, and so are the sources that describe them: product labels and trial counts for the scalp products, and for the tablets a few small trials, one large set of clinic records, a case report and labels written for blood-pressure treatment.
This page sets those out by form. Each count comes with the size of its group, each label statement with its country and product, and each section says where the numbers stop. It is written about adult men with male pattern hair loss, and it does not replace the leaflet that comes with a product.
Two routes and two sets of side effects
In the United States the men's 5% solution and foam are sold over the counter, and in the United Kingdom the men's foam is on general sale. The tablets are authorised in both countries for high blood pressure, so taking them for hair loss is off-label and goes through a prescriber. [1, 2, 3, 4, 5]
Scalp products and tablets, side by side
What our sources recorded for each route. The counts come from one trial, which had no foam group.
| Question | Solution or foam5%, applied to the scalp | TabletsLow dose, taken by mouth |
|---|---|---|
| Where it acts | On the scalp. Some reaches the bloodstream: the UK labels report about twice as much with the 5% solution as with the 5% foam. | The whole body. |
| Highest count we extracted | Unwanted hair growth away from the scalp, in 11 of 45 men on the solution. | Unwanted hair growth, in 22 of 45 men on 5 mg a day. |
| Skin | Scalp eczema in 7 of 45 men. | Scalp eczema in 1 of 45 men. |
| Headache and swelling | Headache in 1 of 45 men. No swollen legs recorded. | Headache in 6 of 45 men and swollen legs in 1 of 45. |
| Label warnings | The US men's labels list symptoms to stop for, among them chest pain and a rapid heartbeat. | The US tablet label, written for blood-pressure treatment, warns of fluid around the heart and worsening angina. |
| Who decides | The user, within the limits on each label. The US products and the UK foam need no prescription. | A prescriber. No label we checked gives a dose for hair loss. |
Counts are from one 24-week trial of 90 men, 45 in each group, comparing 5 mg by mouth once a day with 1 mL of 5% solution twice a day. A man can appear in more than one row. The numbers describe that trial and are not rates for everyone. [6, 7, 3, 1, 2, 4]
The rest of the page takes each column in turn. What minoxidil does for hair is in the full minoxidil profile, and the tablet has a page of its own: minoxidil tablets for hair loss.
Side effects of the solution and foam
The most useful counts for a scalp product come from the solution group of the trial in the table above: 45 men who used 1 mL of 5% solution twice a day for 24 weeks, together with a dummy treatment by mouth. Unwanted hair growth away from the scalp was recorded in 11 of them, scalp eczema in 7 and headache in 1. Three stopped because of side effects. The men were aged 18 to 55 and had been selected for having no heart or kidney disease. [6]
Irritation, itching and eczema
- Also recorded
- In a 48-week trial of 393 men, itching and local irritation were more frequent with the 5% solution than with the 2%. We could read only its published summary, which gives no counts and does not say who funded it. [8]
Hair growing where it is not wanted
- Not in our sources
- Where on the body it appeared in the men on the solution, and how long it lasted.
- On the label
- The US solution label puts unwanted facial hair among the reasons to stop and ask a doctor. [1]
More shedding in the first weeks
Symptoms in the rest of the body
These categories can overlap, so the counts cannot be added up into a number of men affected. A second, smaller source is a 12-week trial of 36 men who all used 5% minoxidil twice a day. Side effects were recorded in 3 of the 18 men on minoxidil alone and in 6 of the 18 who also had microneedling: itching in 8 men in all, and passing redness in 1 man in the microneedling group. The trial was paid for by a university grant. [9] The labels do not cover putting minoxidil on broken skin, and microneedling with minoxidil is a separate subject.
The liquid base and the foam
Irritation can come from the minoxidil or from what it is dissolved in. The UK and US solutions we checked contain propylene glycol, and alcohol, propylene glycol and the condition of the scalp can each limit how well a solution is tolerated. The UK foam contains no propylene glycol, and neither did the foam tested in the men's trial. That does not make a foam free of irritants: the UK foam label carries its own warning about ingredients that can irritate. [7, 1, 3, 10]
The UK labels also report that, in men, the 5% solution led to about twice as much minoxidil in the blood as the 5% foam. That is a measure of absorption. It does not show that the foam causes half the side effects, and our research holds no side-by-side count of side effects for foam and solution in men. [7, 3]
The one direct comparison of tolerability we have was done in women and changes three things at once. In 113 women followed for 24 weeks, 5% foam once a day brought fewer local reactions than 2% solution twice a day. The strength, the frequency and the base all differed, and we could read only the published summary. [11] The practical differences between the two are set out in foam and solution compared.
Shedding in the first weeks
Some men notice more hair coming out soon after starting. Three of our sources say something about it, and they are three different kinds of source.
Early shedding in three sources
A label statement, a trial count and a look back at clinic records.
- UK foam label
- Weeks 2 to 6A temporary rise in shedding, which the label says usually settles within a couple of weeks.
- Men on 5% solution, one trial
- 7 of 45Temporary shedding in the first two months. On 5 mg by mouth in the same trial it was 4 of 45.
- People starting tablets, clinic records
- 6 of 115New shedding after starting low-dose tablets: 2 of 37 who kept a scalp product going and 4 of 78 who had not been using one.
The clinic records look back at 115 people with pattern hair loss, 63 women and 52 men, seen about 125 days apart on average. Shedding was what patients reported, the two groups were not randomly assigned and they differed before starting, so the figures do not show whether keeping the scalp product going prevents shedding. No funding was declared, and two authors reported ties to drug companies. [3, 6, 12]
The UK foam label goes one step further than describing it. If the extra shedding carries on for more than two weeks, the label says to stop and get advice. That wording belongs to that product, and one trial does not set a timetable for everyone. None of these sources is a reason to treat shedding that keeps getting worse as expected. [3, 6]
How shedding sits against each label's timeline is part of how to use minoxidil.
What the labels say to do when a symptom appears
A label does more than list effects. It says what the user is expected to do. The wording below is paraphrased from four men's labels checked on 29 September 2026, two from the US and two from the UK. [7, 3, 1, 2]
The UK solution label says to stop and see a doctor for body-wide symptoms that include chest pain, a rapid heartbeat, faintness or dizziness, sudden weight gain or swollen hands or feet, and for redness or irritation of the scalp that persists. The UK foam label says the same of its own listed body-wide symptoms and of persistent redness or irritation. Our research does not record the foam label's symptoms one by one, so the leaflet in the pack is the reference. [7, 3]
Chest pain, a rapid heartbeat, faintness or dizziness, unexplained weight gain or swelling
US labels and UK solutionThe US labels say to stop using the product and ask a doctor. The UK solution label says to stop and see a doctor. The UK foam label says the same of its own list, which our research does not record symptom by symptom.The product is swallowed
US solutionThe label says to get medical help or contact a poison control centre straight away.Redness or irritation of the scalp
US solution and both UK labelsThe US solution label says to stop and ask a doctor about scalp irritation or redness. The two UK labels say to stop and see a doctor when redness or irritation persists.Unwanted facial hair
US solutionThe label says to stop and ask a doctor.Extra shedding that lasts more than two weeks
UK foamThe label says to stop and get advice.A scalp that is already inflamed, infected, irritated or painful
All four labelsThe US labels exclude an inflamed scalp, and the solution label spells out a red, inflamed, infected, irritated or painful one. The two UK labels say not to apply the product to an inflamed, infected, irritated or painful scalp, and the foam label asks for a normal, healthy scalp.No regrowth by the label's review point
All four labelsThe US labels say to stop and see a doctor at 4 months. The UK foam label says to stop at 16 weeks, and the UK solution label after one year.
Each line paraphrases a named product: Men's Rogaine Extra Strength 5% solution and Minoxidil 5% (For Men) foam in the US, Regaine for Men Extra Strength solution and foam in the UK. They are instructions on those packs, not advice from us, and they are not a reason to stop a medicine that a doctor has prescribed. [7, 3, 1, 2]
The amounts and review points of the same four products are in the label table of the minoxidil profile.
Side effects of minoxidil tablets
Taken as a tablet, minoxidil acts on the whole body. None of the labels we checked gives a dose for hair loss. The trials below used 1 mg, 2.5 mg or 5 mg once a day, which describes what was tested and not where anyone should start. [4, 5, 6, 13, 14]
The head-to-head trial in men
Ninety men were randomly given a 5 mg capsule by mouth once a day or 1 mL of 5% solution twice a day for 24 weeks, each with a dummy version of the other. Side effects were counted in all 45 men of each group. [6]
Recorded over 24 weeks, 45 men in each group
Unwanted hair growth
22 of 4511 of 45Headache
6 of 451 of 45Scalp eczema
1 of 457 of 45Swollen legs
1 of 450 of 45Temporary shedding, first two months
4 of 457 of 45Stopped because of side effects
1 of 453 of 45
One trial of 90 men aged 18 to 55 at a single centre, selected for having no heart or kidney disease. A man can appear in more than one row. A trial of this size describes its own groups and cannot show how often less frequent events happen. It was funded by the support fund of the Brazilian dermatology society, which the article says had no role in the design, the analysis or the decision to publish. [6]
The differences showed up mostly as hair growing where it was not wanted, and as headaches. Blood pressure and heart rate did not differ significantly between the two groups, a finding that applies to men screened for heart and kidney disease and followed for 24 weeks. Sixty-eight of the 90 finished. Most of those who left did so because the pandemic made attendance difficult, and four because of side effects. [6]
Two tablet doses compared
A second trial gave 100 men either 2.5 mg or 5 mg a day for 24 weeks. The higher dose did not show an advantage on hair counts, which the page on minoxidil tablets covers. Its side effects were recorded at two visits, at week 12 and at week 24. [13]
Recorded at study visits, 50 men on each dose
Unwanted hair growth, week 24
31 of 5039 of 50Swollen lower legs, week 24
0 of 502 of 50Dizziness, week 12
0 of 502 of 50Headache, week 12
5 of 502 of 50Fast heartbeat, week 12
1 of 501 of 50Stopped because of side effects
2 of 501 of 50
One trial of 100 men aged 25 to 55 without heart or kidney disease. Each row except the last is the count at one visit, not a running total for the whole trial. We read the trial's thesis and its supplement, not the journal article, and the thesis is not consistent throughout: its summary says no fast heartbeat was seen, while its table records one case on each dose. The thesis declares no funding, and the trial registry lists institutional support. [13]
Unwanted hair growth was the most reported effect on both doses. According to the thesis, the three men who stopped because of side effects did so for nausea or headache. We give the counts as they stand and draw no conclusion from them about which dose is safer. [13]
What 1,404 clinic records add
The largest source is not a trial. Clinics pooled the records of 1,404 people taking low-dose minoxidil tablets for hair loss, at doses from 0.03 mg to 15 mg, for 7.9 months on average. Of these, 1,065 had their dose adjusted along the way, and the analysis counted each dose separately, which gives 2,469 dose records. The percentages in the paper are shares of those records. [15]
Side effects in clinic records of low-dose tablets
Unwanted hair growth374 of 2,469 dose records
15.1% of dose records
Lightheadedness43 of 2,469
1.7% of dose records
Fluid retention in the legs32 of 2,469
1.3% of dose records
Fast heartbeat21 of 2,469
0.9% of dose records
Headache9 of 2,469
0.4% of dose records
Swelling around the eyes7 of 2,469
0.3% of dose records
Shares of 2,469 dose records from 1,404 people, as published. They are not the chance that one person has the effect, because the same person can be counted at more than one dose. There was no comparison group and other illnesses were not recorded. The authors declared no funding and no conflicts of interest. [15]
The paper reports that 43 patients stopped treatment, 14 because of unwanted hair growth and 29 because of effects elsewhere in the body. Its text calls them patients while its table sets them against the 2,469 dose records, so we give the count and no percentage. No life-threatening events were seen in these records. That is an observation about this group over these months, not proof that such events do not happen. [15]
A small trial in women counted the same kinds of effect. Among 52 women followed for 24 weeks, unwanted hair growth was recorded in 7 of the 26 on a 1 mg tablet and in 1 of the 26 on 5% solution once a day, with swollen shins in 1 woman on the tablet and itching in 5 on the solution. Nobody stopped because of side effects. These are not men's figures. They come from the trial's thesis. The publisher's page names a Brazilian dermatology fund, FUNADERSP, as funder, and one author is a shareholder and director of a company that holds patents on minoxidil tablets. [14]
Minoxidil and the heart
Minoxidil tablets are a blood-pressure medicine, so questions about the heart come with them. Our sources say four different things, and they cannot be merged into one number.
| Source | What it says | What limits it |
|---|---|---|
| US tablet label | A boxed warning about fluid around the heart, which can go on to press on the heart, and about angina getting worse. | Written for resistant high blood pressure. Its doses and frequencies do not carry over to hair-loss use. |
| Trials at hair-loss doses | No significant difference in blood pressure or heart rate between 5 mg by mouth and the solution in 90 men. A fast heartbeat in 1 of 50 men on each dose at week 12 of the dose trial. In the women's trial, average resting heart rate went from 72 to 77 beats a minute on 1 mg, with no fast heartbeat recorded. | Small groups, 24 weeks, and heart or kidney disease kept out of both men's trials. |
| Clinic records | Lightheadedness in 1.7% of dose records, fluid retention in the legs in 1.3% and a fast heartbeat in 0.9%. | No comparison group. Shares of dose records, not of people. Other illnesses not recorded. |
| One case report | Fluid around the heart and lungs, with widespread swelling, in a 40-year-old woman three weeks after starting 0.25 mg a day. She had fibrosing alopecia, which is not pattern hair loss, and was taking several other medicines. It cleared after the tablets were stopped and she was treated in hospital. | One case shows that something can happen. It does not show how often, and it does not prove the tablet was the cause. |
The UK tablet label is also for high blood pressure. How often serious events happen at hair-loss doses is not known from these sources. [4, 5, 6, 13, 14, 15, 16]
For the scalp products, the heart comes up on the labels and not in the trial counts. The two US men's labels put chest pain and a rapid heartbeat among the symptoms to stop for, and the labels we checked call for a professional assessment before use by anyone with known heart disease. [1, 2, 7, 3]
Who the labels say should not use it
Each label defines who the product is for, and the definitions differ by country.
Limits on the men's scalp labels
Two US and two UK products, checked on 29 September 2026.
| On the label | USMen's 5% solution and 5% foamMen's Rogaine Extra Strength; Minoxidil 5% (For Men) | UKRegaine for Men Extra Strength5% solution and 5% foam |
|---|---|---|
| Age | Men aged 18 and over. Not for anyone under 18. | Men aged 18 to 65 for the solution, and 18 to 49 for the foam. |
| Area | The top of the scalp. Not intended for frontal baldness or a receding hairline. | The amount on the label is spread over all the affected areas. |
| Kind of hair loss | Not when the cause is unknown, or when the loss is sudden or patchy. | Our research did not record this point for the two UK labels. |
| Scalp | Not on an inflamed scalp. The solution label spells out red, inflamed, infected, irritated or painful. | Not on an inflamed, infected, irritated or painful scalp. The foam label asks for a normal, healthy scalp. |
| Heart disease | Known heart disease calls for a professional assessment before use. | Known heart disease calls for a professional assessment before use. |
| Other medicines | The solution label says not to use it with other medicines on the scalp. Our research does not record the foam label's wording separately. | Both UK labels restrict use together with other medicines applied to the scalp. The solution label rules it out. |
Paraphrased from each product's own label. These are rules for those packs, not a way of working out what kind of hair loss someone has. Women's products carry separate instructions, and the US labels set their own limits for pregnancy and breastfeeding. [1, 2, 7, 3, 17, 18]
The US wording on the hairline has its own page: minoxidil for a receding hairline.
For the tablets there is no hair-loss label to quote. The US and UK tablet labels are for high blood pressure, and both trials of minoxidil by mouth in men kept out anyone with heart or kidney disease, so they say nothing about men who have either. [4, 5, 6, 13]
In 2025 an international group of 43 hair specialists from 12 countries published a consensus on starting low-dose tablets: how to assess a patient beforehand, which precautions to take and what to monitor. It is expert opinion, several of its authors declared ties to industry, and it did not agree on a single way of stepping the dose up. Our research did not extract its recommendations one by one, so we do not list who it says should not take the tablets. [19]
After stopping
Two questions sit under this heading: what happens to the hair, and what happens to a side effect.
| Question | What our sources say | What they do not say |
|---|---|---|
| Does the regrowth stay? | All four scalp labels say treatment has to continue to keep it. The UK solution label adds that the gain has been reported to disappear within three to four months of stopping. | That timing rests on anecdotal reports, according to the label, and it has not been shown for the foam or the tablets. We found no trial that stopped the tablets and measured what happened next. |
| Does a side effect go away? | In the case report, the fluid cleared after the tablets were stopped and the woman was treated in hospital. | No study we reviewed followed people after stopping to record how long unwanted hair growth, swelling or scalp irritation took to settle. |
The first row is covered in more detail under if you stop in the profile. [7, 3, 1, 2, 16]
The other core option raises its own question here. For finasteride tablets, the UK regulator warns of depression, suicidal thoughts and sexual problems, and says the sexual problems can continue after stopping. The European regulator lists suicidal thoughts as a side effect of the tablets. [20, 21] That is covered in finasteride side effects. It describes what each set of warnings says and is not a ranking of the two medicines, which minoxidil and finasteride compared sets side by side.
What these studies cannot show
- How often serious events happen at hair-loss doses. The trials that gave us counts have 18 to 50 people in a group, and the clinic records cannot give a figure per person.
- What happens over years. The counts on this page come from trials of 12 to 24 weeks. The longest trial we cite ran 48 weeks, the foam trial's open safety phase went to 52, and the clinic records cover about eight months on average.
- Side effects in men with heart or kidney disease. They were kept out of both trials of minoxidil by mouth in men.
- Whether foam causes fewer side effects than solution in men. Our research holds no side-by-side count.
- Whether a lower tablet dose is safer. The dose trial counted effects at single visits, and its report is not consistent throughout.
- Side effects of tablets taken on top of a scalp product, beyond shedding in one set of clinic records. The head-to-head trial tested the two as alternatives.
One more gap is about access, not about the studies themselves. The men's foam trial kept 143 men in an open safety phase up to 52 weeks, of which we read only the summary. We also read only the summary of the 48-week solution trial. [10, 8]
Where to go next
Side effects are one of the eight criteria behind minoxidil's place in our ranking, where it shares the top tier with finasteride. Why counts stay next to their group sizes on this site is explained on the methodology page.
Minoxidil: the full profileWhat the trials measured, the four label instructions, timelines, costs and combinations. Minoxidil tablets for hair lossWhat the trials of minoxidil by mouth measured, and how the tablets compare with the scalp forms. How to use minoxidilLabel instructions, amounts, shedding and how long it takes.