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]https://pubmed.ncbi.nlm.nih.gov/25112173/

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]https://pubmed.ncbi.nlm.nih.gov/24283387/

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]https://pubmed.ncbi.nlm.nih.gov/10534633/

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

So, despite that 40-60% of topical minoxidil users don’t respond to treatment, after averaging out all participants’ hair growth results, most studies on topical minoxidil show that overall hair growth results are statistically improved.

This is the big problem with topical minoxidil: its hair growth outcomes are bifurcated.

On the one hand, we have 40-60% of users seeing zero effect from the drug. On the other hand, we have 40-60% of users seeing big amounts of hair growth. These bifurcated results can average a 20-30% cumulative hair weight change at the one-year mark.

Key Takeaway: despite ~50% of people not responding to 2% or 5% topical minoxidil, most studies show statistically significant improvements to hair counts. This is because a subset of participants are often hyper-responders to minoxidil, which bring up the average hair counts for everyone.

Do Minoxidil’s Results Last Long-Term?

Unfortunately, hair regrowth from topical minoxidil is not necessarily as long-lasting as most would hope.

This is because clinical studies also show that, over time, the efficacy of topical minoxidil wanes – meaning that its hair growth-promoting effects diminish over a number of years, even despite keeping users above the placebo group. ^[6]https://pubmed.ncbi.nlm.nih.gov/12196747/^[7]https://pubmed.ncbi.nlm.nih.gov/2180995/

This was already evident in the above study, which showed a trend downward for cumulative changes to hair weights from weeks 52 to 96. And these results are consistent across other studies. Just see the diminishing regrowth results from this 48-week study on 2% and 5% topical minoxidil versus placebo:^[8]https://pubmed.ncbi.nlm.nih.gov/12196747/

Moreover, here’s a five-year study tracking topical minoxidil’s efficacy, which seems to wane after year one:^[9]https://pubmed.ncbi.nlm.nih.gov/2180995/

Factors Affecting Topical Minoxidil’s Ability To Grow Hair

There are a handful of strategies to improve the effectiveness of minoxidil. If you’re looking for a deep-dive into the science, this article is a great resource.

Otherwise, here are the highlights:

1. Increase the dilution of topical minoxidil to 15%. Clinical studies show that suspected non-responders to 2% and 5% minoxidil tend to see robust hair regrowth at higher dilutions ranging from 10% to 15% minoxidil.
2. Add in minoxidil enhancers. Retinoic acid (i.e., tretinoin) and microneedling both help increase dermal penetration of minoxidil and active more sulfotransferase.
3. Switch to oral minoxidil. Unlike topical minoxidil – which gets sulfated in the skin – oral minoxidil goes through processing in the liver whereby most people have an abundance of sulfotransferase to activate the drug. This leads to dramatically higher response rates – with daily doses of 2.5 mg and higher sometimes promoting 90% response rates in clinical trials.

Many people inside our membership community have used these strategies above to move from minoxidil non-responders to minoxidil hyper-responders. We hope they help you, too.

We hope these recommendations help take your hair growth results to a new level.