Cat's claw
Cat's claw is the name for Uncaria tomentosa and Uncaria guianensis, woody vines from tropical parts of Central and South America.
Also listed as Vincaria, Uncaria Tomentosa, Uncaria guianensis, Cat's Claw Extract
Who needs extra caution?
Cat’s claw may aggravate autoimmune disease and slow blood clotting; NCCIH advises discussion with a clinician before use in these circumstances or around surgery. Use during pregnancy may be unsafe, and breastfeeding safety is poorly known. Possible interactions with blood-pressure medicines and blood thinners are partly theoretical. 1
Side effects and medicines
Reported effects include nausea, diarrhea and stomach discomfort. Case reports describe higher concentrations of some HIV medicines, including ritonavir, with cat’s claw; medication review is therefore important. 2
A separate warning about adulterated products
An October 2026 US poison-center alert described products labeled cat’s claw that contained undeclared potent opioids derived from kratom. This warning concerns adulterated products, not a finding that genuine Uncaria causes opioid overdose. Severe drowsiness or slowed breathing requires emergency help. 3
For information, not individual medical advice. Ingredient studies do not establish the effectiveness of these products.