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Saw Palmetto Side Effects: What to Know

Last reviewed: December 2025

Overview

Saw palmetto is generally well-tolerated with a favorable safety profile compared to prescription BPH medications. Most side effects are mild gastrointestinal symptoms. Importantly, saw palmetto does not appear to significantly affect PSA levels, which is relevant for prostate cancer screening.

Common Side Effects

Gastrointestinal

  • Stomach upset
  • Nausea
  • Diarrhea
  • Constipation
  • Abdominal pain

Prevention: Take with food to minimize stomach upset.

Other Common Effects

  • Headache
  • Dizziness
  • Fatigue

Most side effects are mild and often resolve with continued use.

Compared to Prescription Alternatives

Sexual Side Effects

Saw palmetto:

  • Rare reports of sexual side effects
  • Less common than with prescription medications

Prescription 5-alpha-reductase inhibitors (finasteride):

  • Decreased libido (1-10%)
  • Erectile dysfunction (1-10%)
  • Decreased ejaculate volume

This is a key reason some men prefer saw palmetto.

Other Comparisons

Saw palmetto advantages:

  • Generally milder side effect profile
  • No significant blood pressure effects
  • Doesn’t require prescription monitoring

Serious Side Effects (Rare)

Bleeding Risk

  • May increase bleeding tendency
  • Few case reports of bleeding complications
  • More concern with blood thinners

Precautions:

  • Stop 2 weeks before surgery
  • Use caution with anticoagulants
  • Report unusual bleeding

Liver Effects

  • Rare case reports of liver problems
  • Most cases resolved after stopping
  • Monitor for jaundice, dark urine, fatigue

Allergic Reactions

  • Rare
  • Skin rash, itching
  • Difficulty breathing (severe—seek emergency care)

Pancreatic Effects

  • Rare case reports of pancreatitis
  • Severe abdominal pain warrants evaluation

Effects on Lab Tests

PSA (Prostate-Specific Antigen)

  • Does NOT significantly lower PSA levels
  • This is important: prescription finasteride lowers PSA by ~50%
  • Saw palmetto allows accurate PSA screening
  • Some studies suggest minor PSA effects, but not clinically significant

Other Labs

  • No significant effects on routine blood tests
  • Does not affect liver function tests in most users
  • Does not alter hormone levels detectably in most studies

Drug Interactions

Blood Thinners

  • Warfarin, aspirin, clopidogrel: Potential increased bleeding risk
  • Monitor for signs of bleeding
  • Discuss with doctor before combining

Antiplatelet Herbs/Supplements

  • Garlic, ginkgo, fish oil, vitamin E
  • May compound bleeding risk
  • Use caution with multiple blood-thinning supplements

Hormonal Medications

  • Theoretical interactions with hormone therapy
  • Finasteride, dutasteride
  • Testosterone therapy
  • Discuss with healthcare provider

Oral Contraceptives

  • Not relevant for primary users (men)
  • Theoretical hormone interaction

Who Should Use Caution

Bleeding Disorders

  • May worsen bleeding tendency
  • Consult healthcare provider

Scheduled Surgery

  • Stop 2 weeks before
  • Inform surgical team

Liver Disease

  • Rare liver effects reported
  • Use with caution, monitor

Hormone-Sensitive Conditions

  • Theoretical concerns
  • Discuss with oncologist if prostate cancer history

Long-Term Safety

Extended Use

  • No major long-term safety signals
  • Used for decades in Europe
  • Continue monitoring for new symptoms

No Known Cumulative Toxicity

  • Can be used for years if tolerated
  • Periodic reassessment recommended

Monitoring

What to Watch For

  • Unusual bleeding or bruising
  • Signs of allergic reaction
  • Liver symptoms (yellowing skin, dark urine)
  • Worsening urinary symptoms

Regular Check-ups

  • Continue regular prostate screening
  • PSA tests remain valid while on saw palmetto
  • Digital rectal exams as recommended

When to Stop and Seek Care

Stop saw palmetto and contact doctor if:

  • Signs of bleeding problems
  • Yellowing of skin or eyes
  • Severe abdominal pain
  • Allergic reactions
  • Any concerning new symptoms

Pregnancy and Breastfeeding

Not applicable to target population (men with BPH), but:

  • Women should not use saw palmetto during pregnancy
  • May affect hormone levels
  • Not recommended during breastfeeding

Sources

  • Natural Medicines Database — Saw Palmetto Safety
  • NIH Office of Dietary Supplements
  • Journal of Urology — Saw Palmetto Safety Reviews
  • FDA Adverse Event Reporting System Data
Last reviewed: December 2025