The Best Hair Growth Serums If You're Thinning Out or Shedding a Worrisome Amount

Best Overall: Women's Rogaine 5% Minoxidil Foam

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As Sobel mentioned, this contains FDA-approved minoxidil, the only ingredient proven to trigger new hair growth. This particular product can regrow up to 25 percent more hair, perfect for those dealing with serious thinning or bald spots. The lightweight foam is easy to use daily, although you'll have to use it diligently for a few months to see results — and will have to keep using it in order to maintain those results. (Related: These Vitamins for Hair Growth Will Give You the Rapunzel-Like Locks of Your Dreams)

"This stuff is amazing," exclaimed a reviewer that has been using the foam for four months. "My hair was thinning so bad and I'm only 24 years old. I needed something to help my hair get thicker; try this stuff it will make you feel so much better."

If the treatment foam is out of stock during your next Amazon visit, you can also get it at walmart.com, walgreens.com, or target.com.

Best Budget: Pronexa Topical Hair Loss Serum

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A budget-friendly and Amazon-favorite pick, this hair loss serum earns rave reviews for working quickly and effectively (and reviewers also love the pleasant scent). It uses a patented pea sprout extract that's rich in nutrients good for your scalp and hair. According to a brand-backed clinical study, 95 percent of users noticed reduced hair loss after three months, though the brand does offer a complete money-back guarantee if you're not totally satisfied with your results.

Speaking to its fast-acting formula, one shopper wrote, "After only two weeks you see the small growth especially on the top where I literally have had no hair." Another said, "This is the second bottle that I ordered and have noticed that my hair loss has diminished. When I wash my hair, I used to see a lot of hair on my comb and now I see very little."

Best Lightweight: Rene Furterer Triphasic Reactional Concentrated Serum

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Hill is a fan of this lightweight serum, which uses a variety of plant-based ingredients (including lemon essential oil) to boost scalp circulation. Since continued use of any of these treatments is essential for best results, Hill also likes how simple this is to apply. To that point, it also needs to be used just once per week for three months. (Psst, you can read more rave reviews calling the Rene Furterer Serum a 'miracle treatment' here.)

One Dermstore shopper wrote, "It's super easy to use. Once a week I apply it to my scalp after towel drying my hair. I then massage it in for a couple of minutes. At about week five or six I noticed new hairs had come in and my overall hair was growing faster. I'm very pleased with the results."

Best for Thickening: Vegamour Gro Hair Serum

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"This serum can visibly increase hair density up to 50 percent while reducing loss from combing and washing by up to 76 percent in four months," says Friese. This is thanks to several unique ingredients not found in many other hair growth serums — namely, mung bean and red clover, which have been shown to help inhibit the production of dihydrotestosterone (DHT, a hormone that plays a role in hair loss), and nicotiana benthamiana, an Australian plant whose proteins have been shown to increase the density of hair roots, she explains.

The Gro Hair Serum has become a fan-favorite thinning hair solution and has received glowing reviews from shoppers. One Vegamour customer said, "I definitely saw accelerated hair growth using this product. Stress caused me to shed a lot, this helped me regrow." Another added, "Three months in, and [my] bald spots are covered with baby hairs! The product is easy to apply and doesn't leave a [greasy] residue, which is so important to me since I have oily hair."

Best Strengthening: Pura D'Or Hair Thinning Therapy Energizing Scalp Serum Revitalizer

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An Amazon fan-favorite boasting more than 1,100 five-star ratings, this features many of the ingredients experts recommend. The 15 different actives include (but are not limited to) biotin — which Friese says can strengthen the hair follicle — and circulation-boosting and DHT-inhibiting caffeine. A targeted nozzle makes application easy, and reviewers rave about how much it improves the thickness and overall quality of their hair. (FWI, this is the serum that Amazon shoppers say reversed their hair loss in just two weeks)

"This definitely does what it says," a shopper began their review. "It has brought my hair breakage from quite a lot to little or none. I definitely recommend it to anyone who wants to strengthen their hair, and reduce hair breakage. This is a mainstay in my hair regimen from now on." Another mentioned that "the amount of hairs that fall off my hair has greatly, greatly reduced" and that "there's lots of new hair growth and my hair is so much thicker now."

Best for Bald Spots: BosleyMD Follicle Energizer

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This powerhouse serum relies on a litany of different ingredients to improve the look and feel of your strands. "Protective botanical extracts make for thicker, fuller-looking hair, biotin strengthens, while rosemary extract helps to reduce scalp inflammation and increase circulation," says Friese, who advises using it on targeted areas rather than all over. "With this product, I like to tell people, 'If you want hair, put it there.'"

Best for Shedding: Aveda Invati Advanced Scalp Revitalizer

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For those seeking instant gratification, this multitasking product is choice. The Invati Advanced Scalp Revitalizer instantly thickens and lifts hair at the root so strands appear fuller right away, making it double as a styling product as well as a hair loss treatment. Its concentrated nozzle guarantees precision when applying and over time, the plant- and herb-based formula, which is rich in invigorating hair-healthy ingredients like turmeric and ginseng, works to support the keratin in your strands. This helps to ward off breakage and subsequent shedding.

"Best hair product," one Amazon reviewer said. "It really helps my hair from shedding." Another was happy to report that the treatment spray "saved my hair" and added, "I was losing my hair and this stopped it. My hair is now to the middle of my back and thick. I use it once a day and it's wonderful."

Best for Itchy Scalps: Groh Stimulating Scalp Serum

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This hair growth serum relies on a blend of ergothioneine — a mushroom-derived amino acid — and vitamin D2. "Humans only get these nutrients from our diets, since the body doesn't produce them naturally, which makes this topical treatment an excellent choice for hair issues caused by dietary deficiencies," says Hill. In addition to stopping fall out and promoting regrowth, the Stimulating Scalp Serum helps rebalance and soothe the scalp, which is ideal for anyone who may be fighting flakes as well. (Pro tip: Pair it with one of the best thinning hair shampoos for even stronger results.)

One customer wrote, "Within three months I had new growth and although it was a little hard to tame...it was well worth it. My hairdresser even mentioned how much new hair I have. Finally, something that works!"