Most of the “best hair growth products” lists I’ve read rank serums and gummies by star rating or by sales. I’ve rarely seen one stop to ask why the reader’s hair is thinning, even though that’s the only thing that tells you whether a product has any chance of working for you.

Take someone whose shedding started three months after a bad flu. Say they order the DHT blocker sitting at the top of one of those lists. Their scalp isn’t dealing with a DHT problem at all, so I’d expect two months of no change, after which they’d be forgiven for deciding hair products are a waste of money. That’s why my answer to “what should I buy?” starts with the cause and moves to the evidence for that cause, with brand names coming up last.

Where in the hair cycle things go wrong

The way I explain it to patients is that each hair grows for years and then rests for a few months before it falls out, and different kinds of hair loss break that cycle at different points.

When someone tells me they had a high fever in the spring, I can usually guess the next part of the story. A large batch of their follicles switched to resting at the same moment, and months later those hairs started coming out together. Shashikant Malkud’s review of telogen effluvium, published in the Journal of Clinical and Diagnostic Research in 2015, puts the usual gap at three to four months, which is long enough that most people end up blaming a new shampoo instead of the fever.

Pattern hair loss works on a slower clock. The follicle doesn’t stop, it shrinks a little with each cycle, under the influence of DHT, and the hairs it produces get finer and shorter until some of them barely clear the scalp.

So when I pick up a product, the first thing I want to know is which of those two problems it was designed for, and it’s rare for the label to say.

The table I’d sketch for a patient

Cause	Usual signs	Best evidence	MDhair
Telogen effluvium	Shedding everywhere, months after a trigger	Find the trigger; check iron	Restore line
Pattern loss	Part or crown, over years	Minoxidil	Regrowth kits
Hormonal shifts	Pattern thinning plus cycle changes	Lab workup, sometimes prescription care	Premium Regrowth Kit
Postpartum	Heavy shedding 2 to 4 months after birth	Time, nutrition	Restore + Supplements
Alopecia areata, scarring	Round patches, scalp pain	A dermatologist	None

I’ll go through each row below, with my view on where an over-the-counter product earns its place.

Shedding after a trigger (telogen effluvium)

Picture someone who had COVID in March. By June or July, hair starts coming out in the shower in quantities that genuinely frighten them. The part looks wider and the ponytail feels thinner, yet if I could look at that scalp up close I’d expect the loss to be spread evenly across it, with the follicles all still in place and simply between hairs.

My first question in that situation isn’t about products. It’s about blood work. The 2015 review I mentioned is direct on this point: increased shedding on its own doesn’t tell you the cause, and a proper diagnosis needs a history plus lab tests, partly to rule out a thyroid problem, which is one of the more common hidden causes I see.

Iron gets particular attention. Wilma Bergfeld’s group at the Cleveland Clinic reviewed the literature on iron deficiency and hair loss in 2006 and concluded that the relationship was real enough to justify checking iron stores in people with shedding, even though the evidence was not yet conclusive. If your periods are heavy, or you eat little red meat, I’d want your ferritin measured before you spend money on anything else.

What about biotin, the ingredient on the front of half the bottles in the aisle? The most useful answer I know of came from Leslie Castelo-Soccio’s group in Philadelphia, who in 2017 went looking for every published case of biotin helping someone’s hair. Each case they turned up involved a person who was deficient, or who had a condition causing the deficiency, and that’s a rare situation for anyone eating ordinary meals, so while a sensible dose won’t hurt you, I’d never let biotin on the label be the reason you pick one bottle over another.

If the trigger is behind you and your labs are normal, telogen effluvium tends to resolve on its own as the follicles cycle back into growth. That takes months, which is a long time to stand around doing nothing, and it’s where a nutrient-replenishing routine makes sense to me as support rather than as a cure.

At MDhair, that’s the job of the Restore line. Restore Supplements contain a broad vitamin and mineral blend, and the ingredient I’d point to first is iron, for the reasons above. Our own product guidance positions them for thinning after an illness or a stretch of restrictive dieting. Our guidance also says they shouldn’t be combined with a separate multivitamin, since the overlap could take iron and other minerals past safe limits. Restore Serum is the topical half of that pairing, and what I like about it for regrowth after shedding is the copper peptide and ginseng base, with rice and oat proteins helping the fine new hairs hold on to moisture while they’re still fragile.

Thinning at the part or crown (androgenetic alopecia)

When the thinning sits at the part or the crown and has crept along for years, I can be more definite than anywhere else in this article, because one ingredient has far more trial data behind it than the rest. Areeba Adil and Marshall Godwin gathered the placebo-controlled trials into a single meta-analysis, which the Journal of the American Academy of Dermatology published in 2017, and topical minoxidil beat placebo in every group they examined, down to the 2% strength used by women. Minoxidil is also the only ingredient in this article with OTC drug status for this use in the US.

If your part has been widening for a couple of years and minoxidil isn’t somewhere in your routine, I’d ask why. It has real drawbacks. It needs to be used daily, indefinitely, and many people see a temporary increase in shedding in the first weeks as old hairs make way for new ones. But nothing sold without a prescription has a stronger evidence base for this cause.

Where do botanicals fit? Saw palmetto is the one I’m asked about most, and it appears in MDhair’s Regrowth and Restore serums as well as our Regrowth Supplements. Nine studies and 381 patients went into a systematic review that Natasha Mesinkovska’s team at UC Irvine published in 2020, and the results leaned positive. One topical trial reported a 27% rise in hair count at 50 weeks against about 14% on the vehicle, and an oral trial in women with self-perceived thinning found terminal hair count up 10.4% at six months against 3.5% on placebo. The authors were careful to add that most studies were small and that robust efficacy data are still missing. In the one head-to-head trial, saw palmetto did less than finasteride. My read is that it’s a reasonable supporting ingredient with a plausible mechanism, and I wouldn’t present it as a replacement for minoxidil.

Rosemary has a smaller evidence base, though an interesting one. A group in Iran randomized adults with pattern hair loss to rosemary oil or 2% minoxidil for six months, and when the results appeared in SKINmed in 2015, hair counts in the two groups were statistically similar, with less scalp itching on rosemary. A single trial isn’t enough to call rosemary a minoxidil substitute. It is enough to explain why rosemary leaf oil appears in our Regrowth Serum.

For this cause, MDhair’s Regrowth kits are the match. The Essential Regrowth Kit pairs Regrowth Serum with Regrowth Shampoo, the Advanced kit adds Regrowth Supplements, and minoxidil (2.0% for women, 5.0% for men) can be added alongside any of them. Regrowth Serum was formulated for sensitive, dry scalps, with tea tree oil to calm itching, so it’s often the better fit for anyone who found earlier products irritating, and our instructions are to use it and minoxidil at different times of day instead of layering one wet product over the other.

When hormones are part of the picture

A patient’s periods turn irregular at 42, and over that same year her part widens. The thinning itself looks like pattern loss. What sets it apart is the company it keeps, whether that’s cycle changes from perimenopause or the jawline acne that often comes with polycystic ovary syndrome.

If that combination sounds familiar, I’d see a doctor for labs before choosing a product, and I’d say that more firmly here than anywhere else in this article. Thyroid is the first thing I’d want ruled out, because an underactive thyroid can keep hair shedding no matter what you put on your scalp. And when PCOS turns out to be behind it, the most effective option may be a prescription drug that blocks androgens at the receptor, which is a decision to make with your physician.

With the hormonal side under a doctor’s care, our Premium Regrowth Kit is the broadest option we make, with everything in the Advanced kit plus Marine Collagen for strand support. Its supplements carry saw palmetto, aimed at the hormone signal from the inside, along with ashwagandha root extract, an adaptogen sometimes used for stress. Two cautions belong right here, not at the bottom of the page. Our label rules the supplements out for anyone pregnant, trying to conceive, or breastfeeding. It also asks people on hormone-related medication to talk to their doctor before the first capsule, a request that extends to anyone on blood thinners or managing a thyroid condition.

Postpartum shedding

If you’re three months past delivery and pulling handfuls of hair from the drain, the American Academy of Dermatology’s advice is the first thing I’d point you to: it treats this shedding as normal and expects most people to have their usual fullness back by the baby’s first birthday. The volume comes from the pregnancy itself, when high estrogen held hairs in the growing phase for months longer than usual, so after the birth a large number of them reach the resting phase at once and come out over the following weeks.

Time does most of the work here, so my focus is on not making things worse. Iron is the thing I’d keep an eye on, since blood loss at delivery can lower it at exactly the moment a new parent is eating irregularly and sleeping badly.

In MDhair’s range, the match is the Restore line, with Restore Supplements at its center once pregnancy is over, and Restore Serum’s moisture-binding proteins help the short new hairs that come in over the following months. A few points need saying plainly. Restore Supplements aren’t meant for use during pregnancy. If you’re breastfeeding, talk to your doctor first. And if you’re still taking a prenatal vitamin, it already supplies iron, so the two shouldn’t be combined without medical advice. Our Regrowth Supplements, by contrast, are off the table entirely while breastfeeding.

When no product is the answer

A smooth, round bald patch the size of a coin is something I’d want to see in person, because it usually means alopecia areata, where the immune system turns on the follicles. Brett King’s team at Yale tested baricitinib, an oral JAK inhibitor, in two phase 3 trials, and by the time they reported in the New England Journal of Medicine in 2022, many patients with severe disease had regrown a large share of their scalp hair. I don’t know of a serum or supplement with anything close to that for this condition.

Burning or pain on the scalp worries me for a different reason. Along with scaling, or redness and small bumps at a receding hairline, it can point to a scarring alopecia, where the follicle is destroyed for good. Early treatment matters, and cosmetic products can delay it.

How I’d read a product’s claims

Much of the marketing language around hair growth would survive a fact-check and still tell you nothing useful. “Clinically tested” can mean tested for skin irritation rather than for regrowth. “Up to 90% of users saw thicker hair” often comes from a self-reported survey with no control group.

When I evaluate a product, the question I ask first is whether its claim rests on a controlled trial of that exact formula, measured objectively with hair counts or imaging. A study of one ingredient at a dose the product doesn’t contain tells you very little. After that, I want to know what the product was compared against, and I give more weight to a comparison with an established product than to a placebo alone.

That’s also the standard I try to hold our own data to. The clinical trial my team and I ran was a six-month, third-party, IRB-approved study of MDhair’s AI-personalized regimen, published in the Journal of Drugs in Dermatology in 2025. At 90 days, participants showed roughly 2.8 times the improvement in hair growth compared with the leading hair loss supplement brand. Hair quality improved about 3.0 times as much against that same comparator. Under scanning electron microscopy, hair strand damage moved from Grade 2, with lifted and cracked cuticles, to Grade 0, an intact cuticle, after six months of treatment. Those are results from one specific study against one specific comparison, and I’d encourage you to read any brand’s figures, ours included, with that framing in mind.

A note on regulation

I’ll be specific about regulation, because it’s easy to blur. Of everything I’ve mentioned, minoxidil alone holds OTC drug status, and only for mild-to-moderate androgenetic hair loss. The serums and supplements I’ve described sit in cosmetic or supplement territory instead, which means the FDA hasn’t reviewed them the way it reviews a drug, and none of them is meant to diagnose, treat, cure, or prevent disease.

In practice, two habits follow from that. If you’re pregnant, nursing, or managing a medical condition, bring your doctor into the decision before adding something new. And if a product irritates your scalp, stop using it rather than pushing through.

If you’re still not sure which row of the table describes you, MDhair’s free assessment is a sensible place to start. You answer a short quiz about your hair history and take a scalp photo, and the AI analysis suggests the likely cause behind your thinning before matching you to a kit, with dermatologist chat support included if your regimen needs adjusting along the way. You can take the quiz here.

Dr. Yoram Harth is a board-certified dermatologist and Co-Founder and Chief Medical Officer of MDalgorithms Inc., the company behind MDhair and MDacne. A magna cum laude graduate of Tel Aviv University's Sackler School of Medicine, he trained in dermatology at Rambam Medical Center and completed a research fellowship at Columbia-Presbyterian Medical Center in New York. His work spans phototherapy, photodynamic therapy, and AI-personalized skin and hair care.

Sources

1. Malkud S. Telogen effluvium: a review. J Clin Diagn Res. 2015;9(9):WE01-WE03. doi:10.7860/JCDR/2015/15219.6492
2. Trost LB, Bergfeld WF, Calogeras E. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. J Am Acad Dermatol. 2006;54(5):824-844. doi:10.1016/j.jaad.2005.11.1104
3. Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disord. 2017;3(3):166-169. doi:10.1159/000462981
4. Adil A, Godwin M. The effectiveness of treatments for androgenetic alopecia: a systematic review and meta-analysis. J Am Acad Dermatol. 2017;77(1):136-141.e5. doi:10.1016/j.jaad.2017.02.054
5. Evron E, Juhasz M, Babadjouni A, Mesinkovska NA. Natural hair supplement: friend or foe? Saw palmetto, a systematic review in alopecia. Skin Appendage Disord. 2020;6(6):329-337. doi:10.1159/000509905
6. Panahi Y, Taghizadeh M, Marzony ET, Sahebkar A. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. SKINmed. 2015;13(1):15-21. PubMed
7. American Academy of Dermatology. Hair loss in new moms. https://www.aad.org/public/diseases/hair-loss/insider/new-moms
8. King B, Ohyama M, Kwon O, et al. Two phase 3 trials of baricitinib for alopecia areata. N Engl J Med. 2022;386(18):1687-1699. doi:10.1056/NEJMoa2110343
9. Bhardwaj V, Rodgers N, Harth O, Harth Y. Artificial intelligence-based personalization of treatment regimen for hair loss: a 6-month clinical trial. J Drugs Dermatol. 2025;24(3):233-238. doi:10.36849/JDD.8611

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