Saw palmetto can cause stomach upset, headache, dizziness, nausea, constipation, or diarrhea, though many people tolerate it without much trouble. The biggest practical concern is what you take alongside it: blood thinners and hormone-based medicines deserve a conversation with your prescriber or pharmacist before you combine them.
Saw palmetto comes from the berries of Serenoa repens, a small palm native to the southeastern United States. It is commonly used in supplements marketed for prostate and urinary support, and it also appears in some hair products.
What side effects can saw palmetto cause?
The side effects most often reported are digestive upset, headache, dizziness, nausea, vomiting, constipation, and diarrhea. Taking a capsule with food may be easier on your stomach if nausea or stomach discomfort is the issue.
| Possible effect | What it may feel like | What to do |
|---|---|---|
| Digestive upset | Nausea, stomach discomfort, constipation, diarrhea, or vomiting | Review the label and discuss persistent symptoms with a clinician. |
| Headache or dizziness | Head pain, lightheadedness, or feeling off balance | Pause and ask a pharmacist or prescriber how it fits with your medicines. |
| Bleeding concern | Unusual bruising or prolonged bleeding, especially with medicines that affect clotting | Contact your prescriber promptly. |
| Allergic reaction | Severe rash, swelling of the face, lips, tongue, or throat, or trouble breathing | Seek urgent medical care. |
Healthline’s saw palmetto overview also lists dizziness, headache, nausea, vomiting, constipation, and diarrhea among possible side effects. For a broader look at supplement safety questions, see our guide to turmeric side effects.
What is saw palmetto used for?
People most often use saw palmetto for urinary symptoms associated with an enlarged prostate, including frequent urination, a weak stream, and nighttime bathroom trips. It is also marketed for hair loss and hormone-related concerns.
The answer on prostate symptoms is less simple than the marketing can make it sound. Harvard Health’s review of saw palmetto describes a one-year trial of 225 men taking 160 mg twice daily that found no difference from placebo, followed by a larger 72-week trial that tested doses up to 960 mg daily and also found no better symptom improvement than placebo. Those results matter if you are taking it for frequent urination or a weak stream: do not assume the supplement explains a change in urinary symptoms.
Can saw palmetto affect hormones, testosterone, or estrogen?
Saw palmetto is often described as affecting hormone pathways, especially the pathway involving dihydrotestosterone (DHT). But the mechanism is not settled. The large trial discussed by Harvard notes that anti-androgenic and anti-inflammatory actions have been proposed, not conclusively proven.
That means there is no clear basis to promise that saw palmetto will raise or lower testosterone in women, lower testosterone in men, or increase estrogen. If your reason for considering it is hair loss, acne, menopause symptoms, low libido, or a hormone result on a lab report, bring the specific product label to your clinician or pharmacist first.
Can you take saw palmetto while on HRT or birth control?
Do not treat this as a routine supplement combination. Healthline notes that saw palmetto may interfere with contraceptive medicines and that its hormone activity is a concern with estrogen-containing products. Hormone replacement therapy can involve estrogen, progesterone, or both, so confirm the combination with the prescriber or pharmacist who manages your HRT before taking it.
Is saw palmetto safe while breastfeeding?
Healthline says the FDA urges pregnant and breastfeeding women to avoid saw palmetto because of its hormone activity. If you are breastfeeding, ask your obstetric clinician, pediatric clinician, or pharmacist about a specific product before using it.
What should you not mix with saw palmetto?
The most important pairing to address is medicine that affects blood clotting. Harvard Health says saw palmetto may interfere with the blood’s ability to clot, and Healthline lists aspirin, clopidogrel, heparin, warfarin, diclofenac, ibuprofen, and naproxen among medicines that can slow clotting. The concern is bruising or bleeding. Confirm the combination with the prescriber or pharmacist before taking them together.
Also ask before combining saw palmetto with hormone therapy, estrogen-containing birth control, finasteride, dutasteride, or a multi-ingredient prostate or hair supplement. This is especially important because blends can contain several ingredients with their own interaction questions. Our men’s supplement safety guide explains why checking every ingredient matters.
Does saw palmetto affect sleep or make you pee more?
Sleep disturbance is not among the common side effects listed by Healthline. The 72-week prostate-symptom trial included sleep-quality measures and found saw palmetto no better than placebo on its secondary outcomes.
Saw palmetto is commonly taken because people hope it will help urinary frequency, not because it is meant to make you urinate more. If you begin having more frequent urination, a weaker stream, pain, blood in urine, fever, or worsening nighttime trips, get medical advice rather than trying to solve it by changing a supplement dose.
How long does saw palmetto take, and should you take it morning or night?
There is no single best morning-or-night schedule established by the research here. In the 72-week trial, participants were asked to take their gelcaps together at a convenient time. For an over-the-counter product, follow its label and choose a consistent time that fits your routine.
Doctronic’s medication guide says people commonly wait four to six weeks before judging changes in urinary symptoms. The more useful checkpoint is whether the symptom you are tracking has changed and whether another medical cause needs attention; the larger controlled trials described above did not find saw palmetto superior to placebo for urinary symptoms.
What about saw palmetto for hair loss?
Hair-loss products often use saw palmetto because of the proposed DHT pathway. A PubMed-indexed review of androgenetic alopecia studies describes limited research using varied saw palmetto formulas and routes, so a shampoo, scalp lotion, and oral capsule are not interchangeable.
If you are considering it for hair loss, decide first whether you are looking at a topical product or an oral supplement. Then check the full ingredient list, directions, and whether it contains other active ingredients. Oral supplements bring the interaction questions above; topical products may irritate sensitive skin.
Before you take saw palmetto
- Check whether you use aspirin, warfarin, clopidogrel, heparin, or another medicine that affects clotting.
- Ask about the combination if you use HRT, estrogen-containing birth control, finasteride, dutasteride, or a hormone-related medicine.
- Avoid self-treating new or worsening urinary symptoms with a supplement alone.
- If you are pregnant or breastfeeding, ask your clinician or pharmacist before using it.
- Choose one product at a time and keep the label available so your pharmacist can review the exact ingredients.
Disclosure: DeanSilverMD.com may earn compensation from some links on this site. That relationship does not change the information in this guide.
By DeanSilverMD.com Editorial Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.