Marie Claire's Best Treatment for Thinning Hair: Hårklinikken's Hair Gain Extract

Harklinikken — (Image credit: Hårklinikken)

I've long envied Danish women for many reasons: their ultra-chic outfits, their effortlessly healthy lifestyle, and, oh, their gorgeous locks. Thick, full, and luscious is truly everything I want my hair to be. (I'd also love to dye my hair a bright Scandi blonde shade, but that's beside the point.) Anyway, I was curious to know which products are in a Danish haircare routine, and what I found surprised me. The key to healthy, thick tresses isn't a secret homemade remedy, a pricey salon visit, or even an overnight fix, but a personalized scalp treatment. You may have already seen Hårklinikken's famous Hair Gain Extract featured in Marie Claire's 2025 Hair Awards, where it won Best Treatment for Thinning Hair—but in case you didn't, keep reading to learn why it's worth checking out.

Hårklinikken

Hair Gain Extract

Decades of research, thousands of five-star reviews, and endless before-and-after photos prove this serum is worth the hype.

Hårklinikken is differentiated by its longevity-driven approach to hair health. Instead of overnight fixes, the brand focuses on sustainable, long-lasting results—in line with the Danish approach to whole-body wellness. This has been the brand's intent from the very beginning. It was founded in 1992 in Copenhagen by hair-biology expert Lars Skjøth, who was one of the first to recognize the link between scalp health and hair health more than 27 years ago. While some brands just recently jumped on the scalp health trend, Skjøth spent over 30 years researching this subject, culminating in the creation of Hair Gain Extract. This ultra-targeted treatment method uses a unique science-backed technology that harnesses the power of botanicals. Soothing marigold and potent burdock root work in synergy to optimize your scalp for hair growth, which not only prevents androgenetic hair loss but also re-engages your follicles to strengthen hair and stimulate growth.

Harklinikken Hair Gain Extract Before and After — Image credit: Hårklinikken

And that's just the start. Each bottle of the Hair Gain Extract is also custom formulated. You can either take a five-minute assessment online, schedule an online consultation, or schedule an in-person consultation at one of the brand's beautiful clinics in New York City, Beverly Hills, Copenhagen, or one of its other locations. This consult takes into account your hair type, scalp biology, lifestyle, environment, and hair goals to create a formula that's completely personalized. Through continuous check-ins, your formula is optimized to maximize the results you see and feel. Science doesn't lie, and neither do the before-and-after photos.

If you want the complete Danish haircare routine, use the shampoo, conditioner, and styling products alongside the Hair Gain Extract, as they all work in unique synergy. When used together as a system, these botanical-powered formulas help you achieve your healthiest scalp and fullest hair yet. It just might be the best-kept secret in the hair industry.

Hårklinikken

Hair Supplement

Nourish your hair from the inside out with this daily supplement. With biotin, ashwagandha, and amino acids, it targets eight key contributors of hair loss, including thinning, shedding, stress, and nutrient deficiencies. Plus, it also supports hair growth, health, strength, and density.

Hårklinikken

Stabilizing Scalp Shampoo

If your scalp needs a reset, this shampoo is it. Burdock root deeply yet gently cleanses the scalp and stabilizes oil production so your products can work more effectively.

Hårklinikken

Daily Conditioner

We all know the importance of barrier health and moisture retention in your skin, and this conditioner brings that to your hair. The formula contains aloe vera and avocado oil, two ingredients that provide intense hydration, reduce breakage, and give your locks a natural luster.

Hårklinikken

Hair Hydrating Crème

This multipurpose formula doubles as a weightless styling cream and hydrating heat protectant. No matter how you use it, the nourishing Abyssinian and argan oils increase strength, elasticity, and hydration while adding shine and vibrancy.

Hårklinikken

Hair Mask

Add this five-star hair mask to your wash-day routine. The emollient-rich formula has a trio of hydrating oils that hydrate and repair damaged or color-treated hair and help protect from future damage and breakage. The nourishing mask hair strengthens and boosts moisture retention, leaving hair softer, smoother, and replenished—all without silicone, color, or perfume.

Emma is an associate beauty editor of branded content. She’s a passionate writer who loves all things beauty, wellness, and personal growth. Before pursuing writing, she worked in influencer marketing at Gallery Media Group, which owns digital brand PureWow. She lives in New York City, where you can usually find her running to a Pilates class or sipping on a green juice in the park.