Saw Palmetto Side Effects

Saw Palmetto Side Effects

Saw palmetto is a popular herbal supplement, especially among men with benign prostatic hyperplasia (BPH). However, like any supplement, saw palmetto may cause side effects. Even though natural remedies are generally considered safe, they can still interact with medications or have adverse effects on certain individuals. By taking the time to educate yourself about the possible side effects, you can make an informed decision and minimize any potential risks.

In general, saw palmetto is safe to take in most situations. Mild side effects such as stomach irritation, diarrhea, or headaches can sometimes occur. Those who are pregnant, on blood thinning medications, or hormonal therapies should take extra caution and consult a physician before taking saw palmetto.

Side Effects of Saw Palmetto in Females

While saw palmetto is more commonly taken by men, some women take it as well. In women, possible side effects of saw palmetto may include:

Headache –

Headaches seem to be one of the more common side effects reported with saw palmetto use, occurring in both men and women. However, the exact frequency is unknown due to limited research.

One small study on saw palmetto for hair growth in women found that 11% of participants reported headaches after taking the supplement for 12 months. Another study examining saw palmetto for urinary symptoms in men found a 3.4% incidence of headaches compared to placebo.

The mechanism behind saw palmetto headaches is not well understood. Some theories include:

  • Hormonal effects – Saw palmetto may impact hormones like testosterone and estrogen, which could theoretically trigger headaches in sensitive individuals. The phytoestrogens in saw palmetto may play a role.
  • Vasodilation – Saw palmetto is believed to relax smooth muscle tissue. This may dilate blood vessels and lead to headaches in some people.
  • Prostaglandin inhibition – Saw palmetto blocks the conversion of arachidonic acid into inflammatory prostaglandins. This may alter vasodilation in the brain and trigger headaches.
  • Toxicity – One case study reported severe headaches from extremely high doses of saw palmetto over a long period. Toxicity is unlikely at typical supplement doses.

The good news is that saw palmetto headaches seem to be mild in most cases. Discontinuing use or lowering the dosage often provides relief. Those prone to frequent headaches may want to use saw palmetto cautiously. As always, it’s best to consult a health professional if significant side effects develop.

Changes in menstrual cycle –

Saw palmetto may impact estrogen levels and lead to changes in menstrual cycle length and flow. This is likely due to its phytoestrogens and potential estrogenic activity.

Here are some more details on how saw palmetto may impact the menstrual cycle:

  • Irregular periods – Some women report changes in menstrual cycle length, such as slightly shorter or longer cycles, after starting saw palmetto. One study found it extended the follicular phase but shortened the luteal phase in some women.
  • Heavier/lighter flow – Saw palmetto may affect estrogen levels, which could theoretically lead to heavier or lighter menstrual bleeding in some individuals. There are anecdotal reports of both effects, but robust data is lacking.
  • Spotting – Due to hormone fluctuations, some women notice intermittent spotting when taking saw palmetto. Spotting may occur mid-cycle or just before menses.
  • Amenorrhea – There are isolated case reports of missed periods or amenorrhea associated with regular saw palmetto use. Discontinuing use seemed to resolve this side effect.
  • Painful periods – Dysmenorrhea, or painful menstruation, may potentially worsen for some women taking saw palmetto. This may be related to prostaglandin inhibition.

The mechanism is believed to involve saw palmetto’s antiandrogenic and estrogenic compounds. It may block testosterone conversion and alter estrogen metabolism. However, research is very limited on saw palmetto’s effects on the menstrual cycle. The evidence for these side effects is weak. More studies are needed to confirm if and how saw palmetto impacts menstruation. As always, consult a doctor with any significant supplement side effects.

Breast tenderness –

There have been some reports of breast tenderness in women taking saw palmetto. Again, this may be related to hormonal effects on breast tissue.

Changes in pregnancy –

Saw palmetto should be avoided during pregnancy, as its safety has not been established. There is a theoretical risk it could impact fetal development. However, animal studies are lacking, and no quality human trials have been conducted. Saw palmetto contains plant compounds like beta-sitosterol that may have mild estrogenic effects. This is concerning during pregnancy when estrogens should be tightly regulated.

While major fetal risks are theoretical, the general recommendation is to avoid saw palmetto during pregnancy until more research is available proving its safety. Women who are pregnant or trying to conceive should consult their doctor before using this supplement.

Interactions with birth control pills –

Saw palmetto may interfere with oral contraceptives and make birth control pills less effective. It may impact hormone levels and absorption of the medication.

While large, high-quality studies on saw palmetto in women are lacking, the risks appear relatively low. However, women who experience significant side effects on the supplement should discontinue use.

Side Effects in Males

In men, the most common side effects of saw palmetto relate to the urinary tract. Potential side effects include:

  • Headaches: Some men report headaches when taking saw palmetto. The cause is uncertain.
  • Dizziness: A few studies show reports of dizziness among men taking saw palmetto. However, incidence seems very low.
  • Nausea, vomiting, or abdominal pain: Gastrointestinal issues may occur in some users, though nausea and related side effects are more often reported with another BPH herb, pygeum africanum.
  • Constipation: Some studies cite constipation as an occasional side effect of saw palmetto supplementation in men.
  • Diarrhea: Loose stools or diarrhea are also possible with saw palmetto, though less common than constipation.

Of greatest concern is the impact on the urinary tract. Potential side effects include:

  • Increased urinary frequency: For some men, saw palmetto may increase urination or urgency to urinate. This may improve BPH symptoms but could also interfere with sleep.
  • Decreased urine flow: There are isolated reports of saw palmetto decreasing urine flow instead of increasing it as intended. This may exacerbate urinary difficulties.
  • Blood in urine: In rare cases, saw palmetto may lead to a minor amount of blood in the urine. The mechanism is unknown.
  • Interactions with ED medications: Saw palmetto may interact with ED drugs like Viagra, making them less effective. It may inhibit their breakdown and increase risk of side effects.

Saw Palmetto Side Effects on Blood Pressure

There are potential interactions between saw palmetto and anticoagulant medications. Saw palmetto may increase the risk of bleeding when combined with anticoagulant drugs like warfarin (Coumadin).

Anticoagulants work by slowing down the body’s ability to form blood clots. Saw palmetto is believed to have mild blood-thinning effects as well. Taking the two together could enhance the anticoagulant effect and make people more prone to excessive bleeding.

One case study reported significantly increased bleeding during surgery in a patient taking both warfarin and saw palmetto. His INR (a measure of blood clotting) was also elevated above therapeutic range. Another report described easy bruising and bleeding gums in someone taking saw palmetto with the anticoagulant ticlopidine.

The mechanism is not totally clear but likely involves saw palmetto’s ability to inhibit platelet aggregation. It may also interfere with vitamin K metabolism which is essential for the clotting cascade.

People taking anticoagulants like warfarin, heparin, dabigatran, rivaroxaban, or apixaban should use saw palmetto cautiously under medical supervision. INR should be monitored closely for increased effects on clotting factors. Signs of bleeding should be reported promptly to a doctor.

Saw Palmetto and PSA

There is some evidence that taking saw palmetto can affect PSA test results:

  • PSA (prostate specific antigen) is a protein produced by the prostate. Elevated levels may indicate prostate cancer or other prostate conditions.
  • Saw palmetto may reduce inflammation and congestion in the prostate. This can lower PSA levels in the bloodstream.
  • Several studies have shown saw palmetto supplementation leads to a decline in PSA of around 10-15% on average after regular use (1, 2).
  • This decline could potentially mask rising PSA levels that may signal developing prostate cancer. However, saw palmetto is not thought to actually affect the progression of cancer.
  • Doctors need to factor in the PSA-lowering effects of saw palmetto when interpreting results and determining if further testing is warranted.
  • Men taking saw palmetto should inform their doctor before getting a PSA test. The same protocol should be used consistently for accurate comparison.
  • Stopping saw palmetto for a period before the PSA test may “unmask” the true PSA levels.
  • There is no evidence saw palmetto interferes with other diagnostic tests for prostate cancer like rectal exams or prostate biopsies.

While saw palmetto may moderately affect PSA scores, it does not appear to obscure diagnosis of prostate cancer when appropriate testing is done. Patients and doctors just need to account for its use when making clinical decisions based on PSA results.

How to Minimize the Risk of Side Effects

To minimize the risk of side effects associated with Saw Palmetto, it is important to follow these guidelines:

  • Consult with a healthcare professional before starting any new supplement or herbal remedy, especially if you have underlying health conditions or are taking medications.
  • Start with a low dose and gradually increase if tolerated well.
  • Monitor your body’s response to Saw Palmetto and be aware of any changes in your health or well-being.
  • Keep track of any medications or supplements you are taking to identify potential interactions.
  • If you experience any concerning side effects, discontinue use and consult with your healthcare professional for further guidance.


No serious side effects of saw palmetto have been definitively proven and, if there are side effects, they are usually mild. Overall, saw palmetto is well tolerated by most people at standard doses when taken as directed. As with any supplement, it’s wise to consult a healthcare provider before use.