Oral minoxidil: when to judge the effect

It’s been six weeks since your doctor prescribed the tablets. And in the shower, you seem to be losing more hair than before. Is the treatment not working? Is it making things worse? Every morning you open the box and wonder how long you’ll have to wait to find out.

Studies and dermatologists give fairly clear benchmarks. They come in three stages: the first few weeks, the third month, then six to twelve months.

The first few weeks

Heavier shedding can appear at the start. A 2025 review of the side effects of low-dose oral minoxidil places it 2 to 4 weeks after starting, usually lasting 3 to 6 weeks¹. Depending on the study, it affects 16% to 32% of patients, a figure the authors believe is an underestimate¹. In a New York study of 115 patients, it was recorded in only 5.2% of them, but that was based on medical records, which are bound to miss some cases².

Why would hair fall out when the treatment is meant to keep it? Minoxidil shortens the hair’s resting phase. Hairs that would have fallen out in the coming weeks or months fall out earlier, all at once². These phases are explained in the hair growth cycle. In a study of 100 women cited by a 2022 review, 22 had this shedding; for most of them, it stopped within 4 weeks, and none stopped treatment because of it³.

There’s a full article on early shedding with oral minoxidil. It also happens with the topical solution.

When an effect may start to show

The first benchmark is the third month. According to Ramírez-Marín and Tosti, oral minoxidil alone may show an initial response after about 3 months of treatment³. That’s a possible start, not a verdict.

Judging takes longer. The Spanish Academy of Dermatology’s consensus asks for treatment of androgenetic alopecia to be kept up for at least 6 to 12 months before assessing whether it works⁴. It’s a general rule, and it applies to the tablet too. The trial that compared tablets and solution in men measured its results at 24 weeks, about 6 months⁵.

This slow pace isn’t specific to the tablet. For the solution, the British Association of Dermatologists also says at least 6 months, possibly 12, before any benefit⁸: it’s all in when to judge topical minoxidil.

What the studies report

A meta-analysis by a Chinese team, published in 2025, pooled 27 studies and 2,933 patients treated with oral minoxidil for various types of hair loss⁶. By its calculations, 47% of patients improved, 35% improved clearly and 26% stabilised; these rates come from different studies and don’t add up⁶.

These figures come with limits, which the authors list themselves: many of the included papers are just letters, there are few randomised trials, improvement was assessed subjectively, and long-term follow-up is poorly reported⁶. The studies lasted from 3 months to more than a year, with no analysis of the effect by duration⁶. The international consensus of 43 dermatologists also points out that this is an off-label treatment⁷. To see how the tablet compares with the solution, read tablet or solution.

The general picture: some people improve; for others, the hair loss stops without visible regrowth; for others still, the effect stays weak. Hair loss that stabilises is already a result, even if the mirror doesn’t show it.

The side effect timeline

Side effects also tend to appear at particular times, according to the review by Jimenez-Cauhe and colleagues¹:

• a fast heart rate or palpitations: mostly in the first three days, most often in the first 24 hours;
• dizziness: mostly in the first week;
• headaches: usually around 15 to 20 days;
• fluid retention, with swollen ankles or face: between 1 and 3 months, most often around 2 months;
• extra hair on the face or body: the most common effect, in 15.1% of patients in the largest study.

Write down what you feel and when. It helps your doctor review things, and if a side effect appears, it’s up to them to decide what happens next.

How to judge, in practice

Don’t judge on one day’s shedding, or on a reflection. In the first few weeks, the amount of hair in the shower tells you little about what comes next. What counts is the state of your scalp compared with day one.

A few traps often skew the comparison. A shorter cut makes the scalp look thinner, and so does wet or flattened hair. Overhead light deepens a parting more than light from the front. And if you change something else at the same time, a shampoo, a supplement or your hairstyle, you won’t know what caused a change. The simplest approach: keep the same routine for these months, and always take photos in the same conditions, with your hair dry and styled the same way.

Three checkpoints are enough: at 3 months to see if anything is starting, at 6 months for a first review, at 12 months to decide. Each time, compare area by area: the parting, the crown, the temples. And remember that treatments for androgenetic alopecia only work for as long as you keep taking them: when you stop, the benefit is lost⁸. Continuing, adjusting or stopping is a decision to make with your doctor, with photos to back it up.

Your photos, month after month

From one week to the next, nothing visibly changes. And under different light, the same scalp looks thinner or fuller. That’s why judging “in the mirror” almost always fails.

With Calvap, you take a comparable photo of each area every week, with the previous one overlaid so you can match the framing. Your first session becomes the reference point. At 3, 6 and then 12 months, you compare it with the latest one, side by side. In your journal, your start date, the early shedding and any side effects you noted line up on the same timeline as your photos.