Regrowth from Minoxidil: How Much Should I Expect?

Technically speaking, “hair regrowth” isn’t a term specific enough to be meaningful. Are we talking about changes to total hair counts? Changes to hair thicknesses? Increases to terminal hairs? Vellus hairs? Hair density changes? Over what time period: 1 month, 3 months, 5 years? What about the percentage of people who notice increased hair growth versus those who don’t?

Depending on how we define “hair regrowth”, our answers will vary wildly.

For these reasons, our team prefers to use more specific language surrounding hair regrowth. Here are the two metrics we tend to consider most important when evaluating the efficacy of a hair loss treatment option:

1. Response Rate. This term can be defined through a question: “Of the people who try this intervention, what percent will see a slowing, stopping, or partial reversal of their hair growth versus a placebo group – and over a reasonable time period?” 
2. Regrowth Rate. This term’s definition varies depending on the quality of data on an intervention. But in general, it’s the change in an objective hair growth endpoint that closely mirrors the perception of “visual improvements” to hair. For instance, this might be the change in terminal hair counts, hair density (i.e., the ∆ in hair counts x the ∆ in hair thickness), or hair weight (i.e., the difference in the weight of hair shaved off before/after a study was conducted, controlling for hair growth timing).

What Is Minoxidil’s Response Rate?

Despite being an FDA-approved hair growth drug, topical minoxidil’s response rate is as low as 40-60%.^[3]

This is because topical minoxidil is applied to the scalp as a pro-drug – meaning that it’s inactive. It needs to come into contact with a skin enzyme called sulfotransferase – which is produced by the SULT1A1 gene – in order to active in the skin, and then attach to hair follicles where it can elicit its hair growth-promoting effects.

Unfortunately, upwards of 60% of men and women do not have high enough levels of sulfotransferase in their skin to elicit a response to topical minoxidil.^[4]

This means that for (potentially) a majority of people who try topical minoxidil, it won’t lead to any hair growth, because not enough of it will activate within the scalp to create an effect on hair growth.

Fortunately, there are ways to enhance minoxidil’s efficacy – and the activity levels of sulfotransferase in the scalp skin. We’ll get into these later in the article.

What Is Minoxidil’s Regrowth Rate?

This depends on a number of factors, including someone’s:

• Gender
• Severity of hair loss
• Genetic variance in the SULT1A1 gene
• The delivery method of minoxidil (oral vs. topical)
• The dosing amount and schedule
• If minoxidil is combined with interventions that might enhance its hair growth-promoting effects (more on this later).

Having said that, if we narrow our definition of Regrowth Rate to changes to “hair weight” occurring over a 1+ year usage period, and we narrow our patient population to healthy men and women who are facing androgenic alopecia, we can use clinical data to set ballpark expectations.

A well-designed study by Price et al. (1999) sought to determine the effect of 2% and 5% topical minoxidil on cumulative hair weight changes throughout 96 weeks of treatment. Compared to the placebo and untreated groups, hair weight changes from 2% and 5% topical minoxidil were 20% and 30% higher for 2% and 5% topical minoxidil users at the 52-week mark, respectively.^[5]

Here’s a chart summarizing the details (Note: participants withdrew from treatment at the vertical line denoted at week 96):