Cat's Claw Tea Side Effects: 7 Things to Know First

Cat's claw has a gentle reputation.

In the Peruvian Amazon, Asháninka families have boiled the inner bark of this woody vine for generations, and in Lima you can buy it by the bag at almost any market herb stall. That long history makes it easy to assume the tea is safe for everyone. For most healthy adults, a cup a day does seem to be well tolerated. But cat's claw works on the immune system, blood pressure and the way your body clears some medicines, so there are real exceptions.

Here are seven things worth knowing before you brew your first cup.

1. The common side effects are mild and mostly in the stomach

The side effects people report most are nausea, loose stools, an upset stomach and, less often, dizziness or a headache. They tend to show up with strong brews or on an empty stomach.

If this happens, try a weaker cup (one tea bag steeped for 5 minutes instead of a long boil) and drink it after food. If the symptoms do not settle within a few days, stop.

2. It can lower blood pressure

Cat's claw (Uncaria tomentosa) contains an alkaloid called rhynchophylline that relaxed blood vessels in lab and animal studies. In practice, that means some people may feel lightheaded, especially when standing up quickly.

If you already take blood pressure medicine, the effects could add up. Check with your doctor first, and watch your readings for the first couple of weeks if you do start.

3. It may slow blood clotting

Some compounds in cat's claw appear to reduce how easily platelets stick together. On its own, that is rarely a problem. Combined with blood thinners such as warfarin, clopidogrel or daily aspirin, it may raise the risk of bruising or bleeding.

For the same reason, stop drinking cat's claw tea at least two weeks before a planned surgery or dental procedure, and tell your surgeon you were taking it.

4. People with autoimmune conditions should be careful

Cat's claw is traditionally used to support the immune system, and lab studies suggest it can stimulate immune activity. That is exactly why it may be a poor fit if your immune system is already overactive.

If you have lupus, rheumatoid arthritis, multiple sclerosis or another autoimmune condition, talk to your doctor before trying it. There is one published case report (Nephron, 2001) of kidney problems in a woman with lupus who took cat's claw, though a single case does not prove the herb caused it.

5. It can clash with immune-suppressing and other medicines

Because it may push the immune system up, cat's claw could work against drugs meant to calm it down, such as those taken after an organ transplant or for autoimmune disease.

There is a second, quieter issue. A 2024 lab study published in PMC found that cat's claw extract blocked several of the "transporters" your body uses to move drugs in and out of cells. Older lab work also suggests it may slow an enzyme (CYP3A4) that breaks down many common medicines. These are test-tube findings, not proof of harm in people, but they are a good reason to ask a pharmacist if you take any daily prescription.

6. Skip it during pregnancy and breastfeeding

There is not enough safety research in pregnancy. Some traditional accounts from the Amazon describe cat's claw being used to prevent pregnancy, which is one more reason to avoid it while trying to conceive, while pregnant, or while breastfeeding. Children should not take it either.

7. Buy the right plant, and do not overdo the dose

Two species are sold as cat's claw: Uncaria tomentosa and Uncaria guianensis. They are related but not identical, and there is also an unrelated African herb called "devil's claw" that often gets mixed up with it. Look for the Latin name on the label.

Most traditional use in Peru is one or two cups a day, often for a few weeks followed by a break. More is not better. Very strong decoctions are more likely to cause stomach upset and dizziness. If you want help choosing between formats, our cat's claw tea vs. capsules comparison covers the differences.

A quick checklist before your first cup

Talk to a doctor or pharmacist first if any of these apply to you:

• You take blood pressure medicine, blood thinners or daily aspirin
• You have an autoimmune condition or take immune-suppressing drugs
• You have had an organ transplant
• You are pregnant, breastfeeding or trying to conceive
• You have surgery coming up in the next two weeks
• You have kidney disease or a bleeding disorder

If none of these fit and you are a healthy adult, cat's claw tea is a reasonable herbal habit to try. Start with one cup a day and see how you feel.

Frequently asked questions

Is it safe to drink cat's claw tea every day?

Most healthy adults seem to tolerate one or two cups a day for several weeks. Long-term daily use has not been studied well, so taking a break every month or two is a sensible habit.

Is cat's claw hard on the liver?

Serious liver problems appear to be rare. There are a few case reports of liver irritation in people taking cat's claw with other products. If you have liver disease, ask your doctor first.

Can cat's claw make you tired or dizzy?

Dizziness is possible, probably from its effect on blood pressure. Sit down, drink water, and try a weaker cup next time.

Does cat's claw interact with coffee or alcohol?

No specific interaction is known. Alcohol can also lower blood pressure, though, so it makes sense not to combine a large amount of both.

The honest bottom line

We sell cat's claw tea, and we also read the safety research. For a healthy adult who is not pregnant and not on the medicines listed above, it is a traditional Amazon tea with mostly mild side effects. For everyone else, a short talk with your pharmacist is the right first step. You can browse related teas in our immune support collection.

These statements have not been evaluated by the Food and Drug Administration (FDA). This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for education and does not replace advice from a qualified health professional.