Cat’s claw (Uncaria tomentosa) is a woody climbing vine native to the Amazon rainforest. Indigenous populations in Peru and other South American regions have used it medicinally for centuries, brewing tea from the bark and roots to address various ailments.

The name comes from its curved thorns, which look like a cat’s claws. These thorns help the vine climb trees in the rainforest canopy, sometimes reaching heights of 30 metres.

I should be upfront: cat’s claw sits in that awkward space occupied by many traditional remedies. Local use spans hundreds of years, but the clinical research remains limited. Most studies are small, and the mechanisms by which it might work are not fully understood.

What exactly is cat’s claw?

Cat’s claw belongs to the Rubiaceae family, the same family as coffee plants. Two species are commonly used: Uncaria tomentosa and Uncaria guianensis. Commercial supplements typically contain Uncaria tomentosa, extracted from the root bark.

The vine contains dozens of active compounds, including:

Oxindole alkaloids: These are considered the primary active constituents. There are two types (pentacyclic and tetracyclic), and they appear to have different immunological effects
Quinovic acid glycosides: May have anti-inflammatory properties
Polyphenols: Including flavonoids, proanthocyanidins, and tannins
Triterpenoid saponins: Found in various medicinal plants

The specific alkaloid content varies depending on where the plant was grown, what part was harvested, and how it was processed. This variability makes comparing studies difficult, since different products may have quite different chemical profiles.

What does the research actually show?

I’ve gone through the clinical evidence for cat’s claw. Here is what the trials actually found.

1. Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune condition where the immune system attacks the joints, causing inflammation, pain, and progressive joint damage. It affects roughly 1% of the population globally, with women three times more likely to develop it than men.

One randomised, double-blind trial followed 40 patients with rheumatoid arthritis over 52 weeks [1]. All participants were already on standard medication (sulfasalazine or hydroxychloroquine). Half also received cat’s claw extract (60 mg daily), while half received placebo.

The results: those taking cat’s claw had fewer painful joints compared to controls. The difference was statistically significant, though modest.

A few things worth noting about this study. First, it was small (40 participants). Second, all participants continued their regular medication, so we are looking at cat’s claw as an add-on therapy, not a replacement. Third, the reduction in painful joints did not translate to improvements in other measures like morning stiffness or grip strength.

My honest assessment: there may be something here, but one small trial is not enough to draw firm conclusions. If you have rheumatoid arthritis and are considering cat’s claw, discuss it with your rheumatologist first. Do not stop your prescribed medications.

2. Osteoarthritis

Osteoarthritis differs from rheumatoid arthritis. Rather than an autoimmune attack, it involves gradual wear and breakdown of joint cartilage. The World Health Organisation estimates that 10% of men and 18% of women over 60 have symptomatic osteoarthritis, making it one of the leading causes of disability in older adults.

A randomised, double-blind trial tested cat’s claw in 45 people with knee osteoarthritis over four weeks [2]. Participants received either cat’s claw extract or placebo.

The findings: cat’s claw reduced pain during physical activity and improved medical and patient assessment scores. However, it did not reduce knee pain at rest, knee pain at night, or knee circumference (a measure of swelling).

Four weeks is a short trial period. Osteoarthritis is a chronic condition, and we do not know whether these modest benefits would persist with longer use. The sample size was also small.

For context, glucosamine and chondroitin have been studied far more extensively for osteoarthritis, with mixed results. Cat’s claw has less supporting evidence than either of those.

3. Adjuvant therapy during breast cancer chemotherapy

This application is quite specific. Researchers wanted to see whether cat’s claw could reduce some of the side effects of chemotherapy in breast cancer patients.

A randomised trial enrolled 40 women with stage II breast cancer who were receiving a standard chemotherapy regimen [3]. Half received cat’s claw extract (300 mg daily) alongside their chemotherapy, while half received chemotherapy alone.

The results showed that women taking cat’s claw experienced less neutropenia (a drop in white blood cells that commonly occurs with chemotherapy and increases infection risk). The cat’s claw group also showed evidence of reduced DNA damage in their cells.

This is interesting, but I want to be careful about how I present it. This study does not suggest that cat’s claw treats cancer. What it suggests is that it might help mitigate some of the collateral damage from chemotherapy. That is a very different claim.

Anyone undergoing cancer treatment should discuss any supplements with their oncologist. Some supplements can interfere with chemotherapy drugs, so professional guidance is essential.

Benefits with insufficient evidence

Cat’s claw has been promoted for many other conditions, including:

General immune support
Digestive problems
Viral infections (including HIV)
Allergies
High blood pressure

For these uses, I could not find robust clinical trials in humans. Most of the evidence comes from laboratory studies or traditional use, neither of which reliably predicts effects in people. I would not recommend cat’s claw for any of these purposes based on current evidence.

Side effects

Short-term use of cat’s claw appears to be reasonably well-tolerated in most people, based on the limited trial data available. Reported side effects include:

Headache
Dizziness
Nausea and vomiting
Diarrhoea
Skin rash

These side effects were generally mild in the clinical trials. However, the trials were short (typically 4-12 weeks), so we lack data on long-term safety.

One case report documented worsening motor symptoms in a patient with Parkinson’s disease who took cat’s claw [4]. The symptoms improved after stopping the supplement. Whether this was a direct effect or coincidence is unclear, but it is worth noting.

Safety precautions (12 contraindications)

Cat’s claw has several important drug interactions and contraindications. If any of these apply to you, avoid cat’s claw or consult your doctor first.

Medical conditions requiring caution:

Pregnancy and breastfeeding: Safety has not been established. Avoid use.
Autoimmune conditions: This includes multiple sclerosis, lupus, and rheumatoid arthritis (paradoxically, despite the positive trial). Cat’s claw may stimulate immune activity, potentially worsening autoimmune flares. The one positive rheumatoid arthritis trial used cat’s claw alongside immunosuppressive medication, which may have mitigated this risk.
Bleeding disorders: Cat’s claw may have anticoagulant effects, increasing bleeding risk.
Low blood pressure: Cat’s claw may lower blood pressure further.
Leukaemia: Some sources suggest cat’s claw could worsen leukaemia, though the evidence is limited.
Planned surgery: Stop cat’s claw at least two weeks before any scheduled surgical procedure due to potential effects on blood clotting and blood pressure.
Parkinson’s disease: Based on the case report mentioned above, use caution.

Drug interactions:

Blood pressure medications: Cat’s claw may enhance their effects, potentially causing blood pressure to drop too low. This includes ACE inhibitors (captopril, enalapril), ARBs (losartan, valsartan), calcium channel blockers (diltiazem, amlodipine), and diuretics (hydrochlorothiazide, furosemide).
Immunosuppressants: Cat’s claw may counteract these medications. Examples include azathioprine, ciclosporin, tacrolimus, mycophenolate, and corticosteroids like prednisone.
CYP3A4 substrates: Cat’s claw may inhibit this liver enzyme, potentially increasing blood levels of various medications. This includes statins (lovastatin), antifungals (ketoconazole, itraconazole), and sedatives (triazolam).
Antiretroviral medications for HIV: Cat’s claw may affect drug levels, potentially reducing effectiveness. Examples include atazanavir, ritonavir, and saquinavir.
Anticoagulant and antiplatelet drugs: Combined use may increase bleeding risk. This includes warfarin, heparin, enoxaparin, aspirin, clopidogrel, and NSAIDs like ibuprofen and naproxen.

Dosage considerations

The clinical trials used various doses:

60 mg daily for rheumatoid arthritis
Unstated dose for osteoarthritis trial
300 mg daily for the chemotherapy adjuvant study

Commercial supplements typically contain 250-1000 mg per dose. The lack of standardisation makes it difficult to recommend a specific dose. If you decide to try cat’s claw, starting at the lower end of the typical range seems prudent.

The bottom line

Cat’s claw has a long history of traditional use in South America, but the modern clinical evidence remains thin. Small trials suggest possible benefits for rheumatoid arthritis and osteoarthritis, and one study found it might reduce chemotherapy side effects. These findings are preliminary and need replication in larger trials.

The supplement has a notable list of potential drug interactions and contraindications. Anyone taking medications or with underlying health conditions should consult a healthcare provider before use.

Compared to better-studied supplements like curcumin or boswellia for joint health, cat’s claw has less supporting evidence. If you are looking for natural approaches to arthritis, those options have more research behind them, though they are not without their own limitations.

References

Mur E, et al. Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of uncaria tomentosa for the treatment of rheumatoid arthritis. J Rheumatol. 2002;29(4):678-681. PMID: 11950006
Piscoya J, et al. 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;50(9):442-448. PMID: 11603848
Santos Araújo Mdo C, et al. Uncaria tomentosa-adjuvant treatment for breast cancer: clinical trial. Evid Based Complement Alternat Med. 2012;2012:676984. PMC: 3395261
Cosentino C, Torres L. Reversible worsening of Parkinson disease motor symptoms after oral intake of Uncaria tomentosa (cat’s claw). Clin Neuropharmacol. 2008;31(5):293-294. PMID: 18836348
NHS. Herbal medicines. https://www.nhs.uk/conditions/herbal-medicines/
Hardin SR. Cat’s claw: an Amazonian vine decreases inflammation in osteoarthritis. Complement Ther Clin Pract. 2007;13(1):25-28. PMID: 17210508