Cat's claw
Summary
Cat's claw is an Amazonian vine bark. Two small trials from 2001–2002 reported less knee pain on activity in osteoarthritis (45 people, 4 weeks) and fewer painful joints in rheumatoid arthritis (40 people, 24 weeks). Other human data are small biomarker or cancer-care studies. NIH flags possible bleeding, blood-pressure and immune effects, and pregnancy concerns.
Key facts
- Inner bark of Uncaria tomentosa (most US products) or Uncaria guianensis, woody vines of Central and South America[7]
- 45 adults with knee osteoarthritis: pain on activity and overall scores fell within the first week versus placebo; pain at rest did not change (4 weeks)[1]
- 40 patients already on sulfasalazine or hydroxychloroquine: painful joints fell 53.2% versus 24.1% on placebo at 24 weeks[2]
- There is no conclusive evidence from studies in people that cat's claw works for any health purpose[7]
- A systematic review found cat's claw raised levels of some antiretroviral drugs[8]
- 6 graded human outcomes on this page
- October 13, 2026
How it works
ProposedLab work shows cat's claw extracts quench free radicals and block TNF-alpha production at very low concentrations, with weaker effects on prostaglandin E2. Extracts also activate the pregnane X receptor, which controls the drug-metabolising enzyme CYP3A4. How these lab effects translate to people is not established.[1][9]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Cancer care | Grade D | Improved | Open-label · n = 51 · 2015 | 3 rows |
| Osteoarthritis | Grade D | Improved | RCT · n = 45 · 2001 | 1 row |
| Rheumatoid arthritis | Grade D | Improved | RCT · n = 40 · 2002 | 1 row |
| Immune markers | Grade D | Improved | RCT · n = 12 · 2001 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Quality of life and fatigue in advanced cancer | Improved | Grade D | Open-label trial · n = 51 · 2015 Adults with advanced solid tumours and no further treatment options (Brazil) Form: Dry Uncaria tomentosa extract · Dose: 100 mg three times daily (300 mg/day) · Duration: Not stated in the abstract Overall quality of life, social functioning and fatigue scores improved; inflammatory markers did not change and no tumour responses were seen. | 25495394 (opens PubMed)Source [4] |
| Knee pain on activity in osteoarthritis | Improved | Grade D | RCT · n = 45 · 2001 Adults with knee osteoarthritis in Peru (30 cat's claw, 15 placebo) Form: Freeze-dried Uncaria guianensis · Dose: Daily capsules (amount not stated in the abstract) · Duration: 4 weeks Pain on activity and physician and patient assessment scores fell versus placebo, starting in week 1; pain at rest or at night and knee swelling did not change. No effects on blood counts or liver tests. | 11603848 (opens PubMed)Source [1] |
| Blood counts and side effects during colorectal-cancer chemotherapy | No effect | Grade D | RCT · n = 43 · 2012 Adults with colorectal cancer on FOLFOX4 chemotherapy (Brazil) Form: Uncaria tomentosa extract · Dose: 300 mg/day · Duration: 6 chemotherapy cycles No change in blood counts, oxidative-stress or immune markers, or adverse events versus chemotherapy alone; no toxic effects. | 21869902 (opens PubMed)Source [6] |
| Tender and swollen joints in active rheumatoid arthritis | Improved | Grade D | RCT · n = 40 · 2002 Adults with active rheumatoid arthritis on sulfasalazine or hydroxychloroquine (Austria) Form: Uncaria tomentosa extract, pentacyclic oxindole alkaloid chemotype · Dose: Purified extract (amount not stated in the abstract) · Duration: 24 weeks double-blind, then 28 weeks open-label Painful joints fell 53.2% with the extract versus 24.1% with placebo (p = 0.044); swollen joints improved only in the open-label phase. Only minor side effects. | 11950006 (opens PubMed)Source [2] |
| Neutropenia during breast-cancer chemotherapy | Improved | Grade D | RCT · n = 40 · 2012 Women with stage II invasive ductal breast cancer on FAC chemotherapy (Brazil) Form: Dry Uncaria tomentosa extract · Dose: 300 mg/day · Duration: 6 chemotherapy cycles Neutropenia caused by chemotherapy was smaller in the cat's claw group than in the chemotherapy-only control group. | 22811748 (opens PubMed)Source [5] |
| DNA repair after lab-induced damage (biomarker) | Improved | Grade D | RCT · n = 12 · 2001 Healthy adults in Sweden working in the same environment Form: C-Med-100 aqueous Uncaria tomentosa extract · Dose: 250 or 350 mg/day · Duration: 8 weeks DNA damage after a hydrogen-peroxide challenge fell and DNA repair rose versus unsupplemented controls; no toxic effects on blood tests. | 11515717 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Uncaria tomentosa bark extract (capsules, tablets, tea) | Varies[3][4][5] | No human absorption data were found in the cited sources; trials used dry or aqueous bark extracts.[3][4][5] | Trials of 250–350 mg/day for up to 8 weeks reported no toxic effects on blood tests; NIH considers short-term oral use (up to 6 months) likely safe.[3][7] | Immune biomarkers, cancer-care and rheumatoid arthritis trials |
| Freeze-dried Uncaria guianensis | Varies[1] | No human absorption data were found in the cited sources.[1] | No effects on blood or liver tests versus placebo over 4 weeks.[1] | Knee osteoarthritis trial |
Studied doses
Doses studied in human trials ranged from 250–350 mg/day of an aqueous extract (C-Med-100, 8 weeks) and 300 mg/day of dry extract (during chemotherapy and in advanced cancer) to 700 mg/day (350 mg twice daily for 2 months) in a vaccine-response study; the arthritis abstracts do not state the amount.[3][4][5][10]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Anticoagulants and antiplatelet drugsNIH fact sheetNIH notes cat's claw may slow blood clotting and lists anticoagulant and antiplatelet drugs among theoretical interactions; it advises telling the surgical team before an operation. No combination studies exist.[7]
- Blood-pressure medicinesNIH fact sheetNIH lists blood-pressure drugs among theoretical interactions; combined effects on blood pressure have not been studied.[7]
- ImmunosuppressantsNIH fact sheetNIH notes cat's claw might make the immune system more active (its stated concern is autoimmune disease); by extension it could work against immune-suppressing treatment. Extracts also activate PXR, the switch for CYP3A4 that clears tacrolimus and ciclosporin. Both concerns are theoretical: neither has been measured in patients on these drugs.[7][9]
- Antiretrovirals (HIV medicines)ReviewA systematic review of human studies and case reports found cat's claw significantly increased levels of some antiretrovirals and advised monitoring for side effects.[8]
- Other CYP3A4 substratesReviewCat's claw extracts activated PXR in cell assays, which can change CYP3A4 activity and drug levels; clinical relevance is unknown.[9]
Who should be careful
- Pregnancy and breastfeeding
- NIH reports that some studies of cat's claw during pregnancy suggest it is unsafe, and little is known about breastfeeding.[7]
- Autoimmune disease
- Because cat's claw might make the immune system more active, NIH advises people with autoimmune disease to talk to their clinician first.[7]
- Upcoming surgery or bleeding disorders
- Cat's claw may slow blood clotting; NIH advises telling the surgical team.[7]
- Transplant recipients and people on immunosuppressants
- Possible immune activation and CYP3A4 effects could interfere with anti-rejection drugs.[7][9]
- Kidney disease
- A biopsy-proven case of acute interstitial nephritis was linked to a diet shake containing Uncaria tomentosa; kidney function recovered after stopping it and steroid therapy.[11]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Check the speciesMost US products are Uncaria tomentosa; the osteoarthritis trial used Uncaria guianensis.[1][7]
- Extract type mattersTrials used specific preparations (a pentacyclic-alkaloid extract for rheumatoid arthritis, the aqueous C-Med-100 extract for immune markers, studied by its developer's group); results may not carry over to generic bark powder.[2][3]
- AmountHuman studies used 250–700 mg/day of extract.[3][4][5][10]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
What is cat's claw used for?
It is promoted for osteoarthritis, rheumatoid arthritis, immune support and viral infections, but NIH finds no conclusive evidence for any use.[7]
Does cat's claw help knee osteoarthritis?
One 4-week trial in 45 people found less pain on activity, but no change in pain at rest. That is too little evidence to rely on.[1]
Does it help rheumatoid arthritis?
In 40 patients already on standard drugs, painful joints fell more than with placebo over 24 weeks. The authors called it a small preliminary study.[2]
Is cat's claw safe with blood thinners?
Caution is warranted. NIH notes it may slow clotting and could interact with anticoagulant and antiplatelet drugs.[7]
Is it safe in pregnancy?
NIH reports that some studies suggest cat's claw is unsafe in pregnancy.[7]
Is it hard on the liver?
LiverTox, the NIH liver-injury database, says cat's claw has not been implicated in liver injury.[12]
Sources
- [1]Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis.. Inflamm Res, 2001. RCT
- [2]Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of uncaria tomentosa for the treatment of rheumatoid arthritis.. J Rheumatol, 2002. RCT
- [3]DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study.. Phytomedicine, 2001. RCT
- [4]Uncaria tomentosa (cat's claw) improves quality of life in patients with advanced solid tumors.. J Altern Complement Med, 2015. open-label
- [5]Uncaria tomentosa-Adjuvant Treatment for Breast Cancer: Clinical Trial.. Evid Based Complement Alternat Med, 2012. RCT
- [6]Uncaria tomentosa for Reducing Side Effects Caused by Chemotherapy in CRC Patients: Clinical Trial.. Evid Based Complement Alternat Med, 2012. RCT
- [7]Cat's Claw. National Center for Complementary and Integrative Health (NIH), 2024. fact-sheet
- [8]Dietary supplement interactions with antiretrovirals: a systematic review.. Int J STD AIDS, 2017. systematic-review
- [9]Identification of PXR Activators from Uncaria Rhynchophylla (Gou Teng) and Uncaria Tomentosa (Cat's Claw).. Drug Metab Dispos, 2023. animal-study
- [10]Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100.. Phytomedicine, 2001. RCT
- [11]Ketogenic-Diet Shake Containing Uncaria tomentosa-Associated Acute Interstitial Nephritis.. Case Rep Nephrol Dial, 2022. observational
- [12]Cat's Claw.. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, 2012. database
What changed
- Independent adversarial review: immunosuppressant interaction reworded so the NIH autoimmune caution is not presented as a demonstrated drug interaction (now marked theoretical); C-Med-100 DNA-repair row now discloses that controls were unsupplemented, not placebo, and that the studies came from the extract developer's group.
- Second-pass self-review: every PMID re-checked against NCBI esummary (title, year, no retraction or expression-of-concern flag), every dose, n and duration re-read against the PubMed abstract or PMC full text, grades held conservative, and interactions limited to what a cited source supports.
- First draft. Source titles and years taken from NCBI E-utilities esummary; abstracts read for every evidence row.