Saw palmetto is one of the most studied plant extracts for hair thinning, and the early results are encouraging. They are not conclusive. Small trials in men and women report better hair counts, density and less shedding. The official US position is that the evidence is still too limited for firm conclusions. We have read the studies, and below we explain what they found, who they tested, how long results took and how to use the supplement safely.
TL;DR
- Small clinical studies of oral and topical saw palmetto report gains in hair count, density and shedding. NCCIH says the evidence is too limited for firm conclusions.
- It is thought to work by inhibiting 5-alpha-reductase, the enzyme that converts testosterone into DHT, the hormone tied to pattern hair loss.
- Studies of women with female pattern hair loss exist, but they are small. Saw palmetto is not advised during pregnancy or breastfeeding.
- Trials ran from 8 weeks to 50 weeks. Plan on months, not weeks, and track your hair so you can judge for yourself.
Table of Contents
- What saw palmetto is and why people use it for hair
- How saw palmetto may act on DHT
- What clinical studies found
- Saw palmetto for women's hair loss
- How long does saw palmetto take to work?
- Forms and doses that have been studied
- Safety, side effects and who should avoid it
- Perspective: why we track before we trust
- How to track whether it is working
- Track your hair with MyHair
- FAQ
- Sources
What saw palmetto is and why people use it for hair
Saw palmetto (Serenoa repens) is a small palm native to the southeastern United States. The berry extract is sold as capsules, softgels and liquid, and it appears in some shampoos, serums and lotions. According to a 2020 systematic review, the extract is mostly fatty acids (70 to 95%), plus phytosterols such as beta-sitosterol, beta-carotene, vitamin E derivatives and polysaccharides.
People reach for it because of the hormone link behind common hair loss. Androgenetic alopecia, which covers male and female pattern hair loss, is driven by DHT acting on susceptible follicles. Daniels and colleagues explain that 5-alpha-reductase enzymes in dermal papilla cells convert testosterone to DHT. DHT binds the androgen receptor more strongly than testosterone does, which is why reducing that conversion is a logical target.
How saw palmetto may act on DHT
The 2020 review describes saw palmetto as a competitive, nonselective inhibitor of both 5-alpha-reductase isoforms. It also reports that the extract blocks DHT from entering the cell nucleus and lowers DHT's ability to bind androgen receptors by nearly 50%. The 2019 review by Daniels et al. attributes the 5-alpha-reductase inhibition to the fatty acids in the extract.
Human data point the same way. In a 16-week placebo-controlled trial of a standardized saw palmetto oil, oral ingestion lowered serum DHT compared with placebo (p<0.001). The authors took that as confirmation of 5-alpha-reductase inhibition in people. Lab work adds that saw palmetto extracts increased cell viability, stimulated hair follicle growth, reduced the inflammatory response and inhibited apoptosis in follicle models. Cell studies are early evidence, so we treat them as a reason the idea is plausible, not as proof.
What clinical studies found
The overview studies
A 2020 systematic review by Evron et al. looked at five randomized trials and two prospective cohort studies. It found positive effects of topical and oral supplements containing 100 to 320 mg of saw palmetto in people with androgenetic alopecia and telogen effluvium. The headline numbers were:
- 60% improvement in overall hair quality
- 27% improvement in total hair count
- increased hair density in 83.3% of patients
- stabilized disease progression in 52%
The JAMA Dermatology review from 2022 adds the detail that matters. In a trial of 19 men with mild-to-moderate pattern hair loss, 60% of the group on an oral saw palmetto extract improved on investigator assessment, against 11% on placebo after 5 months. The difference was not statistically significant, which is expected in a group that small. That is the kind of caveat to keep in mind when you see a big percentage on a product page.
Saw palmetto compared with finasteride
The same JAMA review describes a comparison trial in 100 men with mild-to-moderate pattern hair loss. Finasteride, a prescription 5-alpha-reductase inhibitor, was more effective at improving hair loss. Saw palmetto stabilized hair loss after 24 months. A separate critical review reports that vertex hair growth in a saw palmetto versus finasteride trial was comparable to the drug.
The practical reading: saw palmetto showed a measurable effect in these studies, and finasteride showed a stronger one. If you want a prescription option, a licensed dermatologist or hair restoration doctor is the right person to talk to. You can find hair restoration doctors through our directory.
Topical and combined use
Saw palmetto is not only swallowed. A 2025 review of topical alternatives describes a trial in 60 men and women where a saw palmetto lotion used twice daily raised mean hair count by 17% at week 10 and 27% at week 50. The vehicle group, using the lotion base without the extract, rose 6% and 14%. The same review reports that combining topical saw palmetto with an oral gelatin-cystine supplement added roughly another 50% across all hair growth parameters.
An earlier 24-week cohort of 50 men using a topical lotion, summarized in the 2020 review, found total hair count up 3.4% at 12 weeks and 4.9% at 24 weeks. Terminal hair count rose 21.4% and 74.1% over the same points.
A standardized oil, oral and topical
In the 16-week randomized, placebo-controlled study of a standardized saw palmetto oil, oral use reduced hair fall by up to 29% and topical use by 22.19% from baseline. Hair density rose 5.17% in the oral group and 7.61% in the topical group. Hair fall dropped about 14.65% after 8 weeks and 20.52% after 16 weeks of oral use.
Saw palmetto for women's hair loss
Most older saw palmetto work focused on men, so women often ask whether any of it applies to them. Some newer trials include women directly.
- Female pattern hair loss, topical serum. A 12-week double-blind trial in 26 women compared a plant-based serum containing saw palmetto with 2% topical minoxidil. Both groups had significant increases in mean hair count and hair shaft diameter, and there was no significant difference between them.
- Oral extract, 180 days. In a randomized, placebo-controlled study of a proprietary saw palmetto extract, the active group beat placebo on every primary endpoint. Terminal hair count changed by +18.6 versus -10.1, and total hair density by +25.1 versus -12.2.
- Menopausal women. In that same study, menopausal women on the active product showed significant placebo-adjusted gains in terminal hair count and total hair density.
- Shedding. A 90-day preliminary report from the same program found a 70.7% reduction in shedding in women past childbearing age (15 women).
These trials are small and test specific products, so results will not carry over to every capsule on a shelf. They do show that women's hair loss is an active area of research for saw palmetto, not an afterthought.
Women should read the safety section below before starting. Hormonal effects matter more for women who are pregnant, may become pregnant or use hormonal medicines.
How long does saw palmetto take to work?
Hair grows in cycles, so no supplement changes it overnight. The studies give a realistic picture of the timeline:
| Study | Form | Time points reported |
|---|---|---|
| Standardized oil trial | Oral and topical | Less hair fall and more density at 8 and 16 weeks |
| Topical lotion trial | Topical | Hair count up 17% at week 10 and 27% at week 50 |
| Topical lotion cohort | Topical | Changes at 12 and 24 weeks |
| Oral extract in women | Oral | 90-day and 180-day readouts |
The authors of the 16-week trial note that its length was a limitation. They add that earlier studies of saw palmetto ran longer to detect changes in perceived efficacy and anagen induction, and suggest that prolonged treatment may be needed to establish full efficacy for regrowth. Our advice follows from that: give any approach at least three to six months before judging it, and keep the same routine and lighting when you check.
Forms and doses that have been studied
The 2020 review covers topical and oral products containing 100 to 320 mg of saw palmetto. One cohort in the review used a nutritional compound with 300 mg taken twice daily for 6 months, in 15 men with pattern hair loss and 15 women with female pattern hair loss, severe telogen effluvium, or stress- and diet-related hair loss. Density increased in 83.3% of participants.
Some points for choosing a product:
- Match the form to the study. Results come from specific extracts, including standardized oils and proprietary blends. A product that states its extract type and the amount per serving lets you compare it with the research.
- Check the label for the amount. Doses in trials sit in the 100 to 320 mg range, so a label far outside that is not what was studied.
- Read the full ingredient list. Many hair supplements bundle saw palmetto with other ingredients, which makes it harder to know what is doing what.
- Ask your clinician first if you take any prescription medicine. Our guide to hair growth supplements and what works walks through how we read supplement labels.
If you prefer topical routes, our overviews of hair oils for thinning hair and natural hair growth products cover how to pick formulas.
Safety, side effects and who should avoid it
The NCCIH describes saw palmetto as well tolerated, with mild and infrequent side effects that can include digestive symptoms, dizziness and headache. It has been used safely in research studies for up to 3 years. The 2020 review agrees that most oral side effects are mild and gastrointestinal, such as nausea, constipation and diarrhea.
Specific situations call for more care:
- Pregnancy and breastfeeding. The NCCIH says saw palmetto may be unsafe during pregnancy or while breastfeeding. The Merck Manual advises that women who are pregnant or may become pregnant should not take it, because of potential hormonal effects.
- Blood thinners. The Merck Manual says people on warfarin should be careful, because of a possible risk of liver toxicity or bleeding. Talk to your prescriber or pharmacist before starting.
- Hormonal medicines. The Merck Manual notes saw palmetto may interact with estrogens in oral contraceptives or hormone replacement therapy and reduce their benefit. Ask your gynecologist or pharmacist if you use either.
- Hormonal symptoms. The 2020 review reports vasomotor symptoms in premenopausal women and a suspected link to early menarche in young girls. Parents should not give it to children without a pediatrician's advice.
Tell your doctor about any supplement you take, especially before surgery or when starting a new prescription.
Perspective: why we track before we trust
We built MyHair because hair loss advice usually asks you to believe before you can see anything. Saw palmetto is a good example. The studies are interesting, and some report clear gains in hair count and density. But they test different extracts, doses and people, so a headline percentage never tells you how your own scalp will respond.
That is why we put measurement first. Our AI scan analyzes your hair health and keeps a record, so you can see whether shedding is slowing and density is changing over weeks and months. Whether you try a supplement, a topical or a clinic treatment, you get a baseline and a trend, not a guess.
When your scan points to a need, we recommend products matched to your analysis. If you want professional input, we also list hair clinics and hair restoration doctors, so you can take your results to someone who can examine you in person.
Cyriac
How to track whether it is working
Because results take months, memory is a poor judge. Here is the routine we suggest:
- Take a baseline before you start. Photograph your hairline, crown and part under the same light and at the same angle. Do it the same day each month.
- Change one thing at a time. If you add a supplement, a new shampoo and a scalp serum in the same week, you cannot tell which one mattered.
- Note shedding. Shedding often changes before density does, so a short monthly note on how much hair you see in the shower or on your brush is useful.
- Compare at 3 and 6 months. The studies above report meaningful changes in that range, so this is a fair window to review.
- Bring the record to a professional. If thinning is fast, patchy or comes with scalp symptoms, see a dermatologist. Photos and scan history make that visit more productive.
If your goal is volume while you wait for regrowth, our guide to volumizing products for early thinning is a good companion.
Track your hair with MyHair
Our app scans your hair, assesses its condition, tracks changes over time and suggests products matched to your results. The Free Plan lets you start at myhair.ai, and the monthly plan is $9.99 per month, with a yearly option on the subscription page.
If you would rather speak to a specialist, you can browse hair clinics and decide with your scan history in hand.
FAQ
Does saw palmetto help hair regrowth?
Some small studies report more hair, higher density or less shedding with oral and topical saw palmetto. The NCCIH says these studies are too limited to draw conclusions. Results also depend on the extract used, so treat it as one option to track, not a guarantee.
Can women take saw palmetto for hair loss?
Several recent trials included women with female pattern hair loss and reported gains in hair count and density. Women who are pregnant, may become pregnant or are breastfeeding should avoid it, per the Merck Manual. Anyone using hormonal contraceptives or hormone therapy should check with a doctor or pharmacist first.
How long does saw palmetto take to work for hair loss?
In the studies, changes in hair fall and density were reported from about 8 to 16 weeks, and longer trials ran 6 to 12 months. We suggest reviewing your photos and scans at 3 and 6 months. The authors of the 16-week trial suggest longer treatment may be needed for full effect.
Is saw palmetto the same as a prescription DHT blocker?
No. Both act on 5-alpha-reductase, but in a trial of 100 men reported in the JAMA Dermatology review, finasteride improved hair loss more, while saw palmetto stabilized it after 24 months. Prescription decisions belong with a licensed doctor.
Sources
- NCCIH: Saw Palmetto, Usefulness and Safety
- Evron et al., Natural Hair Supplement: Friend or Foe? Saw Palmetto, a Systematic Review in Alopecia (PMC)
- Drake et al., JAMA Dermatology: Evaluation of the Safety and Effectiveness of Nutritional Supplements
- Sudeep et al., Oral and Topical Administration of a Standardized Saw Palmetto Oil (PubMed)
- Topical Alternatives for Hair Loss: Beyond the Conventional (PMC)
- Tun et al., double-blind randomized trial of a saw palmetto serum in female pattern hair loss
- Ablon, The Safety and Efficacy of a Novel Saw Palmetto Extract (PMC)
- Ablon, 90-day preliminary report (PubMed)
- Park and Lee, Modulation of Hair Growth Promoting Effect by Natural Products (PMC)
- Daniels et al., Can plant-derived phytochemicals provide symptom relief for hair loss? (International Journal of Cosmetic Science)
- Merck Manual Professional Edition: Saw Palmetto