Cat's claw
In one trial of 40 people with rheumatoid arthritis, painful joints fell more than on placebo. A 4-week knee osteoarthritis trial reported less pain with activity, while a meta-analysis found no difference from control. Immune findings come from two small trials without a placebo arm. Trial side effects were few. Case reports describe delirium and a slow heart rate.
- Status
- Dietary supplement in the US. Not FDA-approved as a drug for any condition.
- Also called
- Uncaria tomentosa, Uncaria guianensis, una de gato, uña de gato, C-Med-100
- Taken for
- rheumatoid arthritis, osteoarthritis, arthritis, joint pain, immunity, immune support
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help2
- LimitedOne small trial found cat's claw extract cut painful joints by 53% against 24% on placebo over 24 weeks in adults with rheumatoid arthritis on standard drugs.
- LimitedLimited evidence: two trials without placebo found cat's claw extracts changed immune cell or antibody measures. Neither measured infections.
What people take it for, and what was found
Shown to help2
Rheumatoid arthritis
One small trial found cat's claw extract cut painful joints by 53% against 24% on placebo over 24 weeks in adults with rheumatoid arthritis on standard drugs.
The numbers and sources
- Effect
- In 40 people with active rheumatoid arthritis taking sulfasalazine or hydroxychloroquine, 24 weeks of an extract from the pentacyclic chemotype of Uncaria tomentosa cut the number of painful joints by 53.2% against 24.1% on placebo (p 0.044). When the placebo group switched to the extract for 28 weeks, painful joints (p 0.003), swollen joints (p 0.007) and the Ritchie index (p 0.004) fell [1].
- Population
- 40 adults with active rheumatoid arthritis on standard drugs, over 52 weeks [1].
- Sources
- [1]
- Caveats
- One small preliminary trial. The second phase had no placebo group [1].
Immunity
Limited evidence: two trials without placebo found cat's claw extracts changed immune cell or antibody measures. Neither measured infections.
The numbers and sources
- Effect
- In male volunteers given a pneumococcal vaccine, 350 mg of the extract C-Med-100 twice a day for 2 months raised the lymphocyte to neutrophil ratio and slowed the fall in antibody levels to 12 vaccine serotypes at 5 months, against untreated controls [4]. In women with stage II breast cancer on chemotherapy, 300 mg a day of dry extract reduced chemotherapy-related neutropenia against chemotherapy alone [5].
- Population
- Men at a general practice clinic in New York City [4], and women with invasive ductal breast cancer [5].
- Sources
- [4], [5]
- Caveats
- The abstracts do not report group sizes [4][5]. Neither trial used a placebo, and neither measured infections.
Mixed results1
Osteoarthritis
Limited evidence: one small 4-week trial of a related species eased knee pain with activity, while a review of 2 studies found no difference.
The numbers and sources
- Effect
- In 45 people with knee osteoarthritis, 4 weeks of freeze-dried Uncaria guianensis lowered pain with activity and doctor and patient assessment scores against placebo, with changes in the first week. Pain at rest or at night and knee swelling did not change [2]. A meta-analysis of herbal medicines for osteoarthritis found no difference between Uncaria guianensis and control across 2 studies [3].
- Population
- 30 people on cat's claw and 15 on placebo [2], and adults with osteoarthritis in the meta-analysis [3].
- Sources
- [2], [3]
- Caveats
- Both sources tested Uncaria guianensis, a related species, not Uncaria tomentosa. The trial was short and small [2]. The meta-analysis rated the evidence as low quality [3].
Doses studied
The vaccine study used 350 mg of C-Med-100 twice a day for 2 months [4], and the breast cancer trial 300 mg of dry extract a day across six chemotherapy cycles [5]. The abstracts of the rheumatoid arthritis and knee osteoarthritis trials do not state the dose [1][2].
Risks
Reported risks1
Delirium and slow heart rate
Case reports: a woman stopping a high-dose cat's claw supplement developed delirium and a very slow heart rate, and received a pacemaker.
The numbers and sources
- Effect
- A 53-year-old woman who tried to stop a high-dose over-the-counter cat's claw supplement developed severe insomnia, anxiety and stomach upset, then delirium needing intensive care. Her heart rate stayed at 29 to 40 beats a minute with first-degree heart block, and she received a permanent pacemaker for suspected sick sinus syndrome [6].
- Population
- One case report [6].
- Sources
- [6]
- Caveats
- A single case. Testing pointed to an underlying heart rhythm disorder [6].
Checked, no increase found1
Adverse events in trials
Limited evidence: only minor side effects, and no blood or liver changes, appeared in a few small trials.
The numbers and sources
- Effect
- Only minor side effects were seen over 52 weeks in the rheumatoid arthritis trial [1]. In the knee trial, blood counts, liver function and side effects did not differ from placebo [2]. The vaccine study found no toxic effects on examination, blood chemistry or blood counts [4].
- Population
- Trial participants [1][2][4].
- Sources
- [1], [2], [4]
- Caveats
- Few trials, each small.
Claims tested and not found
- That Uncaria guianensis lowers osteoarthritis symptoms more than control. A meta-analysis of 2 studies found no difference [3].
Sources
- Mur E, Hartig F, Eibl G, Schirmer M. Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of uncaria tomentosa for the treatment of rheumatoid arthritis. The Journal of Rheumatology. 2002. https://pubmed.ncbi.nlm.nih.gov/11950006/
- Piscoya J, Rodriguez Z, Bustamante SA, et al. Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis. Inflammation Research. 2001. https://doi.org/10.1007/PL00000268
- Del Grossi Moura M, Lopes LC, Biavatti MW, et al. Oral herbal medicines marketed in Brazil for the treatment of osteoarthritis: A systematic review and meta-analysis. Phytotherapy Research. 2017. https://doi.org/10.1002/ptr.5910
- Lamm S, Sheng Y, Pero RW. Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100. Phytomedicine. 2001. https://doi.org/10.1078/0944-7113-00046
- Santos Araújo MC, Farias IL, Gutierres J, et al. Uncaria tomentosa-Adjuvant Treatment for Breast Cancer: Clinical Trial. Evidence-Based Complementary and Alternative Medicine. 2012. https://doi.org/10.1155/2012/676984
- Giovane R. Severe Delirium and Refractory Bradycardia Associated With Uncaria tomentosa Toxicity: A Case Report. Cureus. 2026. https://doi.org/10.7759/cureus.114193