Major interaction on record — check this product against your medications before combining. Check your meds →
Dietary supplement

Cat's Claw 500 mg Ingredients & Drug Interactions

by Source Naturals

Cat's Claw 500 mg label
See full label image
Tablet Or Pill Category: Botanical With Nutrients
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 9, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Cat's Claw 500 mg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Cat's Claw 500 mg is a dietary supplement by Source Naturals with 2 active ingredients. Its ingredients are commonly taken for bone health and osteoporosis prevention, dietary calcium deficiency, heartburn relief (calcium carbonate antacids).Based on those ingredients, 1,037 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Cat's Claw Bark Extract, Calcium. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Cat's Claw 500 mg by Source Naturals

Ask about any prescription or over-the-counter medication and we check it for interactions with Cat's Claw 500 mg by Source Naturals — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
Prefer a human? Send your question to our licensed pharmacists — free, answered by email within 24 hours.

HelloPharmacist Scorecard of Cat's Claw 500 mg by Source Naturals

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 12, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 2 of its 2 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains two active ingredients. Calcium supports bone health, helps regulate nerve and muscle function, and plays roles in kidney disease and stomach upset relief.

Cat's Claw Bark Extract — a concentrated form of the Uncaria tomentosa plant — is used traditionally for immune and inflammatory support, though evidence for most of its uses remains limited. The product also includes inactive ingredients (fillers and binders) such as dibasic calcium phosphate, sorbitol, silica, cellulose gum, stearic acid, and magnesium stearate.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: herbal supplement for structural and functional support.
  • We looked for evidence on: Osteoarthritis, Rheumatoid arthritis (RA), Inflammatory bowel disease (IBD), inflammation, immune function, digestive health.
  • The closest evidence on file: Cat's Claw is rated "Insufficient Reliable Evidence To Rate" for Inflammatory bowel disease (IBD) (Natural Medicines).
  • Also on file: Cat's Claw is rated "Insufficient Reliable Evidence To Rate" for Osteoarthritis, Rheumatoid arthritis (RA).

Calcium has established effectiveness for preventing kidney failure, treating stomach upset (dyspepsia), correcting low blood calcium (hypocalcemia), managing high potassium levels (hyperkalemia), and is likely effective for osteoporosis. Cat's Claw Bark Extract, by contrast, lacks sufficient reliable evidence in our data to rate its effectiveness for hay fever, Alzheimer's disease, asthma, osteoporosis, cancer, or chronic fatigue syndrome.

If you're considering this product for one of those conditions, the evidence we hold isn't established.

The evidence, ingredient by ingredient Calcium Cat's Claw

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Calcium is generally well tolerated at recommended doses, though high doses can cause problems. Belching, constipation, diarrhea, bloating, and stomach upset are common when taken by mouth.

Rarely, very high doses raise concerns about kidney stones and a serious condition called calciphylaxis. Some research suggests that calcium intake above 1,500–2,000 mg daily might be linked to increased prostate cancer risk and possibly cardiovascular disease, though this remains debated.

Cat's Claw Bark Extract is generally well tolerated short-term in healthy adults, but long-term safety hasn't been well studied. Case reports have linked it to kidney injury in a few patients.

A clinical trial in advanced cancer patients reported anemia in 12%, and headache, fatigue, insomnia, and nerve damage in smaller numbers — though it's unclear whether the supplement or the underlying disease caused these.

Side effects, ingredient by ingredient Calcium Cat's Claw

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 2 of the 2 matched ingredients can interact with medications — Cat's Claw, Calcium.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; heart-rhythm medications; lithium.
  • For scale: 1,038 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before you start, check with your pharmacist if you take HIV integrase inhibitors (dolutegravir, elvitegravir, raltegravir), the antibiotic ceftriaxone, thyroid hormone (levothyroxine), heart rhythm drugs (sotalol), blood pressure medications, blood thinners (anticoagulants or antiplatelets), immunosuppressants, or Paxlovid. Calcium can reduce the effectiveness of several of these, and cat's claw may interact with blood pressure, immune, and liver-metabolized drugs.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Major medication interactions have been identified, and safety information is well characterized.

Calcium is a core nutrient you likely need, especially for bone health, but its many medication interactions — especially with HIV drugs, antibiotics, thyroid hormones, and heart medications — mean you should check your exact prescriptions before starting. Cat's Claw is used for immune support, though evidence for most claims is thin, and it carries theoretical risks with blood pressure drugs, blood thinners, and immune medications.

Talk to your pharmacist before adding this product if you take any regular medications.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 2 of 2 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Sep 22, 2022.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Cat's Claw 500 mg, straight from the product label.

Brand Source Naturals
Barcode (UPC) 021078003847
Net contents 120 Tablet(s)
Market status On market
Date entered into DSLD Sep 22, 2022
DSLD ID 274527
Product type Botanical With Nutrients
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegetarian, Adult (18 - 50 Years), Women (not pregnant or lactating), Gluten Free, Dairy Free, Sugar Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Cat's Claw 500 mg by Source Naturals, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Tablet(s)
Maximum serving Sizes:
1 Tablet(s)
Servings per container
120
UPC/BARCODE
021078003847
IngredientAmount% DV
Calcium50 mg4%
Cat's Claw Bark Extract500 mg--

Other ingredients: Dibasic Calcium Phosphate, Sorbitol, Silica, modified Cellulose Gum, Stearic Acid, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
FDA Statement of Identity

Herbal Supplement

Formula

Una de Gato Standardaized extract 1.5% oxindole alkaloids (7.5 mg)

Cat's Claw (uncaria tomentosa) is an herb that grows in the rain forests of the Peruvian Amazon where it has been used for centuries by the indigenous Peruvians. Recent research has discovered that its inner bark contains unique active alkaloid constituents known as oxindole alkaloids, that help support the body's immune system.

Suggested/Recommended/Usage/Directions

Suggested Use: 1 tablet 1 to 2 times daily.

Precautions

Warning: Do not use if you are pregnant, may become pregnant, or breastfeeding.

Do not use if either tamper-evident seal is broken or missing.

Keep out of the reach of children.

Formulation

Suitable for vegetarians.

Contains no yeast, dairy, egg, gluten, soy or wheat. Contains no sugar, starch, preservatives, or artificial color, flavor or fragrance.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Brand IP Statement(s)

Copyright SOURCE NATURALS, INC.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Cat's Claw 500 mg by Source Naturals label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Cat's Claw 500 mg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Cat's Claw 500 mg by Source Naturals

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container120 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Calcium

Interacts with
168 drugs
50 mg per serving Form: Dibasic Calcium Phosphate

Calcium is an essential mineral your body needs for strong bones, nerve signaling, and muscle function, and supplements can help fill gaps when diet f...

Calcium monograph & interactions

Cat's Claw Bark Extract

Interacts with
962 drugs
500 mg per serving Form: Oxindole Alkaloids

Cat's claw is a South American vine traditionally used for inflammation, joint pain, and immune support. Some small studies hint it may help with arth...

Cat's Claw Bark Extract monograph & interactions

Other (inactive) ingredients: Dibasic Calcium Phosphate, Sorbitol, Silica, Modified Cellulose Gum, Stearic Acid, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Cat's Claw 500 mg by Source Naturals Drug Interactions

Want to check YOUR meds against Cat's Claw 500 mg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,037Drugs
7 Major 1,030 Moderate

Ingredients driving the most interactions

Cat's Claw Bark Extract 962
Calcium 168

Individual Drug Interactions

The ingredients in Cat's Claw 500 mg interact with 1,037 drugs. Click any drug to see the details.

2 of the 2 ingredients in Cat's Claw 500 mg interact with drugs. Each result below shows which ingredient is responsible. Cat's Claw Bark Extract Calcium

Each ingredient & the kinds of drugs it affects

For each ingredient in Cat's Claw 500 mg with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Cat's Claw Bark Extract6 drug types · 962 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, cat's claw may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Cat's claw contains rhynchophylline and isorhynchophylline. Animal research suggests that these alkaloids can inhibit platelet aggregation. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Antihypertensive Drugs

Theoretically, taking cat's claw with antihypertensive drugs might increase the risk of hypotension.
Cat's claw contains rhynchophylline. In vitro and animal research suggests that rhynchophylline can lower blood pressure. This interaction has not been reported in humans.

Likelihood Probable Evidence D
Calcium Channel Blockers

Theoretically, taking cat's claw with calcium channel blockers might increase the risk of hypotension.
Cat's claw contains various alkaloids, including rhynchophylline, isorhynchophylline, corynoxeine, and isocorynoxiene. Animal research suggests that these alkaloids can lower blood pressure by acting as calcium channel blockers. This interaction has not been reported in humans.

Likelihood Probable Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, cat's claw might increase or decrease the levels and effects of drugs metabolized by CYP3A4.
Cat's claw may affect the clearance of drugs metabolized by CYP3A4. In vitro research shows that cat's claw can inhibit CYP3A4 enzymes. In one case report, a patient taking cat's claw (at an unspecified dose) experienced increased serum levels of atazanavir, ritonavir, and saquinavir, all of which are CYP3A4 substrates. Levels returned to normal 15 days after discontinuation of the cat's claw supplement, suggesting inhibition of CYP3A4 by cat's claw. In contrast, animal research suggests that rhynchophylline, an alkaloid contained in cat's claw, induces CYP3A expression and accelerates the metabolism of nirmatrelvir, the active component in the nirmatrelvir/ritonavir combination product.

Likelihood Possible Evidence D
Immunosuppressants

Theoretically, cat's claw might interfere with immunosuppressive therapy.
In human and laboratory research, cat's claw has been shown to have immunostimulating activity. It stimulates phagocytosis and increases respiratory cellular activity and the mobility of leukocytes. Theoretically, this could interfere with the activity of immunosuppressant medications.

Likelihood Possible Evidence D
Nirmatrelvir/Ritonavir (Paxlovid)

Theoretically, cat's claw may decrease the levels of nirmatrelvir.
Cat's claw contains rhynchophylline. Animal research suggests that this alkaloid induces CYP3A expression, thereby accelerating the metabolism of nirmatrelvir, the active component in the nirmatrelvir/ritonavir combination product. This interaction has not been reported in humans.

Likelihood Possible Evidence D
Cat's Claw Bark Extract full monograph & interactions

Calcium18 drug types · 168 drugs

Ceftriaxone (Rocephin)

Co-administration of intravenous calcium and ceftriaxone can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys.
Avoid administering intravenous calcium in any form, such as parenteral nutrition or Lactated Ringers, within 48 hours of intravenous ceftriaxone. Case reports in neonates show that administering intravenous ceftriaxone and calcium can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys. In several cases, neonates have died as a result of this interaction. So far there are no reports in adults; however, there is still concern that this interaction might occur in adults.

Likelihood Probable Evidence D
Dolutegravir (Tivicay)

Calcium seems to reduce levels of dolutegravir.
Advise patients to take dolutegravir either 2 hours before or 6 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium carbonate 1200 mg concomitantly with dolutegravir 50 mg reduces plasma levels of dolutegravir by almost 40%. Calcium appears to decrease levels of dolutegravir through chelation.

Likelihood Probable Evidence B
Elvitegravir (Vitekta)

Calcium seems to reduce levels of elvitegravir.
Advise patients to take elvitegravir either 2 hours before or 2 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium along with elvitegravir can reduce blood levels of elvitegravir through chelation.

Likelihood Probable Evidence B
Aluminum

Calcium citrate might increase aluminum absorption and toxicity. Other types of calcium do not increase aluminum absorption.
Calcium citrate can increase the absorption of aluminum when taken with aluminum hydroxide. The increase in aluminum levels may become toxic, particularly in individuals with kidney disease. However, the effect of calcium citrate on aluminum absorption is due to the citrate anion rather than calcium cation. Calcium acetate does not appear to increase aluminum absorption.

Likelihood Possible Evidence B
Bictegravir/Emtricitabine/Tenofovir Alafenamide (Biktarvy)

Calcium might decrease levels of bictegravir/emtricitabine/tenofovir alafenamide by reducing its absorption when taken in a fasting state.
Advise patients that bictegravir/emtricitabine/tenofovir alafenamide and calcium can be taken together if taken with food. However, if taken on an empty stomach, bictegravir/emtricitabine/tenofovir alafenamide should not be taken with, or 2 hours after, calcium containing products.

Likelihood Probable Evidence D
Bisphosphonates

Calcium reduces the absorption of bisphosphonates.
Advise patients to take bisphosphonates at least 30 minutes before calcium, but preferably at a different time of day. Calcium supplements decrease absorption of bisphosphonates.

Likelihood Probable Evidence C
Calcipotriene (Dovonex)

Taking calcipotriene with calcium might increase the risk for hypercalcemia.
Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia. Theoretically, combining calcipotriene with calcium supplements might increase the risk of hypercalcemia.

Likelihood Possible Evidence B
Digoxin (Lanoxin)

Using intravenous calcium with digoxin might increase the risk of fatal cardiac arrhythmias.
Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin. However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin.

Likelihood Possible Evidence B
Diltiazem (Cardizem, Others)

Theoretically, calcium may reduce the therapeutic effects of diltiazem.
Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically, calcium might increase this risk of hypercalcemia and reduce the effectiveness of diltiazem.

Likelihood Probable Evidence D
Levothyroxine (Synthroid, Others)

Calcium seems to reduce the absorption and effectiveness of levothyroxine.
Advise patients to take levothyroxine and calcium supplements at least 4 hours apart. Calcium reduces levothyroxine absorption, probably by forming insoluble complexes. Calcium carbonate supplements reduce effectiveness of levothyroxine in patients with hypothyroidism.

Likelihood Probable Evidence B
Lithium

Theoretically, concomitant use of calcium and lithium may increase this risk of hypercalcemia.
Clinical research suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients. Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

Likelihood Possible Evidence B
Quinolone Antibiotics

Calcium seems to reduce the absorption of quinolone antibiotics.
Advise patients to take oral quinolones at least 2 hours before or 4-6 hours after calcium supplements or calcium-fortified foods. Taking calcium at the same time as oral quinolones can reduce quinolone absorption. Calcium binds to quinolones in the gut.

Likelihood Probable Evidence B
Raltegravir (Isentress)

Calcium may reduce levels of raltegravir.
Pharmacokinetic research shows that taking a single dose of calcium carbonate 3000 mg along with raltegravir 400 mg twice daily modestly decreases the mean area under the curve of raltegravir, but the decrease does not necessitate a dose adjustment of raltegravir. However, a case of elevated HIV-1 RNA levels and documented resistance to raltegravir has been reported for a patient taking calcium carbonate 1 gram three times daily plus vitamin D3 (cholecalciferol) 400 IU three times daily in combination with raltegravir 400 mg twice daily for 11 months. It is thought that calcium reduced raltegravir levels by chelation, leading to treatment failure.

Likelihood Possible Evidence B
Sotalol (Betapace)

Calcium seems to reduce the absorption of sotalol.
Advise patients to separate doses by at least 2 hours before or 4-6 hours after calcium. Calcium appears to reduce the absorption of sotalol, probably by forming insoluble complexes.

Likelihood Possible Evidence B
Tetracycline Antibiotics

Calcium seems to reduce the absorption of tetracycline antibiotics.
Advise patients to take oral tetracyclines at least 2 hours before, or 4-6 hours after calcium supplements. Taking calcium at the same time as oral tetracyclines can reduce tetracycline absorption. Calcium binds to tetracyclines in the gut.

Likelihood Probable Evidence C
Thiazide Diuretics

Taking calcium along with thiazides might increase the risk of hypercalcemia and renal failure.
Thiazides reduce calcium excretion by the kidneys. Using thiazides along with moderately large amounts of calcium carbonate increases the risk of milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure). Patients may need to have their serum calcium levels and/or parathyroid function monitored regularly.

Likelihood Probable Evidence C
Verapamil (Calan, Others)

Theoretically, calcium may reduce the therapeutic effects of verapamil.
Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically, use of calcium supplements may increase this risk of hypercalcemia and reduce the effectiveness of verapamil.

Likelihood Probable Evidence D
Calcium Channel Blockers

Intravenous calcium may decrease the effects of calcium channel blockers; oral calcium is unlikely to have this effect.
Intravenous calcium is used to decrease the effects of calcium channel blockers in the management of overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects. But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers.

Likelihood Unlikely Evidence D
Calcium full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Cat's Claw 500 mg, from the product label.

Source Naturals

Name
Source Naturals, Inc.
Street Address
P. O. Box 2118
City
Santa Cruz
State
CA
ZipCode
95062
Web Address
www.sourcenaturals.com
Pharmacist Counseling Corner

Cat's Claw 500 mg by Source Naturals: Common Questions

Does Cat's Claw 500 mg by Source Naturals interact with any medications?
Yes. Based on its ingredients, Cat's Claw 500 mg has a known interaction with 1,037 medications, including 7 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Cat's Claw 500 mg contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Is cat's claw safe during pregnancy?
No. Cat's Claw is rated possibly unsafe in pregnancy due to its traditional use as an abortifacient and lack of safety data. Avoid it while pregnant. Calcium, on the other hand, is important in pregnancy — adequate intake is needed — but stick to recommended amounts unless your doctor says otherwise.
Can I take this while breastfeeding?
Calcium is fine at recommended amounts while breastfeeding and can help meet your body's needs. Cat's Claw should be avoided while breastfeeding due to insufficient safety information.
What side effects might I notice?
Calcium commonly causes belching, constipation, diarrhea, bloating, and stomach upset. Cat's Claw is generally well tolerated in the short term, but headache, fatigue, insomnia, and nerve problems have been reported in a clinical trial of cancer patients — though it's unclear if the supplement caused them.
Does cat's claw actually work?
The evidence we hold shows insufficient reliable data to rate cat's claw for hay fever, Alzheimer's disease, asthma, osteoporosis, cancer, or chronic fatigue syndrome. Its effectiveness for these conditions is not established in our data.
Why does this product have both calcium and cat's claw?
Calcium supports bone health and mineral balance, while Cat's Claw is included for traditional immune and inflammatory support. The product combines them into one tablet, though their interactions with medications differ and require separate attention.
Can calcium give me kidney stones?
Rarely. Kidney stones have been reported with very high calcium doses, though they're uncommon at recommended amounts. Additionally, case reports of kidney injury have been linked to cat's claw itself in a small number of patients.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Cat's Claw 500 mg is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Cat's Claw 500 mg label
Go deeper

The Full Monographs Behind Cat's Claw 500 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Calcium

Interacts with 168 drugs

Calcium is an essential mineral your body needs for strong bones, nerve signaling, and muscle function, and supplements can help fill gaps when diet falls short. Most people do best getting...

Read the full Calcium monograph → Herb & supplement monograph

Cat's Claw

Interacts with 962 drugs

Cat's claw is a South American vine traditionally used for inflammation, joint pain, and immune support. Some small studies hint it may help with arthritis symptoms, but the overall evidence...

Read the full Cat's Claw monograph →
Sources

Sources & How We Checked

Cat's Claw 500 mg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 78 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Calcium 62 references
  1. Shils M, Olson A, Shike M. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, PA: Lea and Febiger, 1994.
  2. Hernandez-Avila M, Gonzalez-Cossio T, Hernandez-Avila JE, et al. Dietary calcium supplements to lower blood lead levels in lactating women: a randomized placebo-controlled trial. Epidemiology 2003;14:206-12.. PubMed
  3. Thys-Jacobs S, Ceccarelli S, Bierman A, et al. Calcium supplementation in premenstrual syndrome: a randomized crossover trial. J Gen Intern Med 1989;4:183-9. PubMed
  4. Maton PN, Burton ME. Antacids revisited: a review of their clinical pharmacology and recommended therapeutic use. Drugs 1999;57:855-70.
  5. Clemens JD, Feinstein AR. Calcium carbonate and constipation: a historical review of medical mythopoeia. Gastroenterology 1977;72:957-61. DOI
  6. Saunders D, Sillery J, Chapman R. Effect of calcium carbonate and aluminum hydroxide on human intestinal function. Dig Dis Sci 1988;33:409-13. PubMed
  7. Friedman PA, Bushinsky DA. Diuretic effects on calcium metabolism. Semin Nephrol 1999;19:551-6.
  8. Koo WK, Walters JC, Esterlitz J, et al. Maternal calcium supplementation and fetal bone mineralization. Obstet Gynecol 1999;94:577-82. DOI
  9. Raman L, Rajalakshmi K, Krishnamachari KAVR, et al. Effect of calcium supplementation to undernourished mothers during pregnancy on the bone density of the neonates. Am J Clin Nutr 1978; 31:466-9. DOI
  10. Murry JJ, Healy MD. Drug-mineral interactions: a new responsibility for the hospital dietician. J Am Diet Assoc 1991;91:66-73.
  11. Chan JM, Giovannucci E, Andersson SO, et al. Dairy products, calcium, phosphorous, vitamin D, and risk of prostate cancer. Cancer Causes Control 1998;9:559-66.
  12. Butner LE, Fulco PP, Feldman G, et al. Calcium carbonate-induced hypothyroidism. Ann Intern Med 2000:132:595. PubMed
  13. Schneyer CR. Calcium carbonate and reduction of levothyroxine efficacy. JAMA 1998;279:750. PubMed
  14. Moser LR, Smythe MA, Tisdale JE. The use of calcium salts in the prevention and management of verapamil-induced hypotension. Ann Pharmacother 2000;34:622-9. PubMed
  15. Singh N, Singh PN, Hershman JM. Effect of calcium carbonate on the absorption of levothyroxine. JAMA 2000;283:2822-5. PubMed
  16. Kahela P, Anttila M, Tikkanen R, Sundquist H. Effect of food, food constituents and fluid volume on the bioavailability of sotalol. Acta Pharmacol Toxicol (Copenh) 1979;44:7-12.. PubMed
  17. Pletz MW, Petzold P, Allen A, et al. Effect of calcium carbonate on bioavailability of orally administered gemifloxacin. Antimicrob Agents Chemother 2003;47:2158-60.. PubMed
  18. Bar-Or D, Yoel G. Calcium and calciferol antagonize effect of verapamil in atrial fibrillation. Br Med J 1981;282:1585-6.
  19. Decktor DL, Robinson M, Maton PN, et al. Effects of aluminum/magnesium hydroxide and calcium carbonate on esophageal and gastric pH in subjects with heartburn. Am J Ther 1995;2:546-52. PubMed
  20. Simoneau G. Absence of rebound effect with calcium carbonate. Eur J Drug Metab Pharmacokinet 1996;21:351-7. PubMed
  21. Peters ML, Leonard M, Licata AA. Role of alendronate and risedronate in preventing and treating osteoporosis. Cleve Clin J Med 2001;68:945-51. PubMed
  22. Bourke JF, Mumford R, Whittaker P, et al. The effects of topical calcipotriol on systemic calcium homeostasis in patients with chronic plaque psoriasis. J Am Acad Dermatol 1997;37:929-34.
  23. Gueguen L, Pointillart A. The bioavailability of dietary calcium. J Am Coll Nutr 2000;19:119s-136s. PubMed
  24. Vella A, Gerber TC, Hayes DL, Reeder GS. Digoxin, hypercalcaemia, and cardiac conduction. Postgrad Med J 1999;75:554-6. PubMed
  25. Bania TC, Blaufeux B, Hughes S, et al. Calcium and digoxin vs. calcium alone for severe verapamil toxicity. Acad Emerg Med 2000;7:1089-96. PubMed
  26. Tseng M, Breslow RA, Graubard BI, Ziegler RG. Dairy, calcium, and vitamin D intakes and prostate cancer risk in the National Health and Nutrition Examination Epidemiologic Follow-up Study cohort. Am J Clin Nutr 2005;81:1147-54. PubMed
  27. Weingarten MA, Zalmanovici A, Yaphe J. Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps. Cochrane Database Syst Rev 2004;(1):CD003548. PubMed
  28. Tavani A, Bertuccio P, Bosetti C, et al. Dietary intake of calcium, vitamin D, phosphorus and the risk of prostate cancer. Eur Urol 2005;48:27-33. PubMed
  29. Giovannucci E, Liu Y, Stampfer MJ, Willett WC. A prospective study of calcium intake and incident and fatal prostate cancer. Cancer Epidemiol Biomarkers Prev 2006;15:203-10. PubMed
  30. Rocephin (ceftriaxone) and calcium interaction. Pharmacist's Letter / Prescriber's Letter 2007;23(10):231005.
  31. Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: randomised control trial. BMJ 2008;336:262-6.
  32. Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341:c3691. PubMed
  33. Calcium supplementation and vascular events. Pharmacist's Letter / Prescriber's Letter 2008;24(3):240306.
  34. Dietary reference intakes for calcium and vitamin D. Institute of Medicine, November 30, 2010. Available at: http://www.iom.edu/~/media/Files/Report%20Files/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Vitamin%20D%20and%20Calcium%202010%20Repo
  35. Coburn JW, Mischel MG, Goodman WG, et al. Calcium citrate markedly enhances aluminum absorption from aluminum hydroxide. Am J Kidney Dis. 1991;17(6):708-11. PubMed
  36. Bradley JS, Wassel RT, Lee L, et al. Intravenous ceftriaxone and calcium in the neonate: assessing the risk for cardiopulmonary adverse events. Pediatrics. 2009;123(4):e609-13. PubMed
  37. Kays MB, Overholser BR, Mueller BA, et al. Effects of sevelamer hydrochloride and calcium acetate on the oral bioavailability of ciprofloxacin. Am J Kidney Dis. 2003;42(6):1253-9. PubMed
  38. Neuhofel, A. L., Wilton, J. H., Victory, J. M., Hejmanowsk, L. G., and Amsden, G. W. Lack of bioequivalence of ciprofloxacin when administered with calcium-fortified orange juice: a new twist on an old interaction. J Clin Pharmacol. 2002;42(4):461-466. DOI
  39. Dickinson, H. O., Nicolson, D. J., Cook, J. V., Campbell, F., Beyer, F. R., Ford, G. A., and Mason, J. Calcium supplementation for the management of primary hypertension in adults. Cochrane.Database.Syst.Rev. 2006;(2):CD004639. PubMed
  40. Jones, B. J. and Twomey, P. J. Requesting patterns for serum calcium concentration in patients on long-term lithium therapy. Int J Clin Pract. 2009;63(1):170-172. PubMed
  41. Levine, M., Nikkanen, H., and Pallin, D. J. The effects of intravenous calcium in patients with digoxin toxicity. J Emerg.Med. 2011;40(1):41-46. PubMed
  42. Castelo-Branco, C., Ciria-Recasens, M., Cancelo-Hidalgo, M. J., Palacios, S., Haya-Palazuelos, J., Carbonell-Abello, J., Blanch-Rubio, J., Martinez-Zapata, M. J., Manasanch, J., and Perez-Edo, L. Efficacy of ossein-hydroxyapatite complex compared with ca
  43. Li K, Kaaks R, Linseisen J, Rohrmann S. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation i
  44. Chung M, Tang AM, Fu Z. Calcium Intake and Cardiovascular Disease Risk: An Updated Systematic Review and Meta-analysis. Ann Intern Med. 2016 Oct 25. PubMed
  45. Nolan CR, Califano JR, Butzin CA. Influence of calcium acetate or calcium citrate on intestinal aluminum absorption. Kidney Int. 1990;38(5):937-41. PubMed
  46. Lewis JR, Radavelli-Bagatini S, Rejnmark L, et al. The effects of calcium supplementation on verified coronary heart disease hospitalization and death in postmenopausal women: a collaborative meta-analysis of randomized controlled trials. J Bone Miner Res PubMed
  47. Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15. PubMed
  48. Lappe J, Watson P, Travers-Gustafson D, Recker R, Garland C, Gorham E, Baggerly K, McDonnell SL. Effect of Vitamin D and Calcium Supplementation on Cancer Incidence in Older Women: A Randomized Clinical Trial. JAMA. 2017 Mar 28;317(12):1234-1243. PubMed
  49. Grove ML, Cook D. Calcium and heart attacks. Doesn't apply to most calcium prescriptions. BMJ. 2010;341:c5003. PubMed
  50. Insentress [package insert]. Whitehouse Station, NJ: Merck Sharp & Dohme Corp.; 2014.
  51. Roberts JL, Kiser JJ, Hindman JT, Meditz AL. Virologic failure with a raltegravir-containing antiretroviral regimen and concomitant calcium administration. Pharmacotherapy 2011;31(10):298e-302e. DOI
  52. Vitekta [package insert]. Foster City, CA: Gilead Sciences, Inc.; 2014.
  53. Storan ER, O'Gorman SM, Murphy A, Laing M. Case Report of Calciphylaxis Secondary to Calcium and Vitamin D<sub>3</sub> Supplementation. J Cutan Med Surg. 2017;21(2):162-163. DOI
  54. Jenkins DJA, Spence JD, Giovannucci EL, et al. Supplemental vitamins and minerals for CVD prevention and treatment. J Am Coll Cardiol 2018;71(22):2570-84. PubMed
  55. Borkenhagen JF, Connor EL, Stafstrom CE. Neonatal hypocalcemic seizures due to excessive maternal calcium ingestion. Pediatr Neurol 2013;48(6):469-71. PubMed
  56. WHO recommendations on antenatal care for a positive pregnancy experience. Geneva: World Health Organization; 2016 (http://www.who.int/reproductivehealth/publications/maternal_perinatal_health/ anc-positive-pregnancy-experience/en/).
  57. Aune D, Navarro Rosenblatt DA, Chan DS, et al. Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies. Am J Clin Nutr. 2015;101(1):87-117. PubMed
  58. Lan T, Park Y, Colditz GA, et al. Adolescent dairy product and calcium intake in relation to later prostate cancer risk and mortality in the NIH-AARP Diet and Health Study. Cancer Causes Control. 2020;31(10):891-904. PubMed
  59. Zhang Y, Li Y, Liu J, et al. Association of Vitamin D or Calcium Supplementation with Cardiovascular Outcomes and Mortality: A Meta-Analysis with Trial Sequential Analysis. J Nutr Health Aging 2021;25(2):263-270. PubMed
  60. Myung SK, Kim HB, Lee YJ, Choi YJ, Oh SW. Calcium Supplements and Risk of Cardiovascular Disease: A Meta-Analysis of Clinical Trials. Nutrients 2021;13(2):368. PubMed
  61. Hetaimish B. Neonatal Calcinosis Cutis After Treatment of Hypocalcemia with Calcium Gluconate: A Report of 2 Cases. Am J Case Rep 2024;25:e943397. PubMed
  62. US Food and Drug Administration (FDA). Biktarvy Prescribing Information. October 2024. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210251Orig1s020lbl.pdf. Accessed July 16, 2025.

See these in context on the Calcium monograph →

Cat's Claw 16 references
  1. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomedicine 2000;7:273-82. PubMed
  3. Sandoval M, Charbonnet RM, Okuhama NN, et al. Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med 2000;29:71-78.
  4. Müller AC, Kanfer I. Potential pharmacokinetic interactions between antiretrovirals and medicinal plants used as complementary and African traditional medicines. Biopharm Drug Dispos. 2011;32(8):458-70. PubMed
  5. Sheng, Y., Bryngelsson, C., and Pero, R. W. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa. J Ethnopharmacol. 2000;69(2):115-126. PubMed
  6. Lamm, S., Sheng, Y., and Pero, R. W. Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100. Phytomedicine 2001;8(4):267-274.
  7. Sheng, Y., Li, L., Holmgren, K., and Pero, R. W. DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine 2001;8(4):275-282.
  8. Chen, C. X., Jin, R. M., Li, Y. K., Zhong, J., Yue, L., Chen, S. C., and Zhou, J. Y. Inhibitory effect of rhynchophylline on platelet aggregation and thrombosis. Zhongguo Yao Li Xue.Bao. 1992;13(2):126-130.
  9. Flythe, J. E., Rueda, J. F., Riscoe, M. K., and Watnick, S. Silicate nephrolithiasis after ingestion of supplements containing silica dioxide. Am.J.Kidney Dis. 2009;54(1):127-130. PubMed
  10. Zhou, J. and Zhou, S. Antihypertensive and neuroprotective activities of rhynchophylline: the role of rhynchophylline in neurotransmission and ion channel activity. J.Ethnopharmacol. 10-28-2010;132(1):15-27. PubMed
  11. Zhou, J. Y. and Zhou, S. W. Isorhynchophylline: A plant alkaloid with therapeutic potential for cardiovascular and central nervous system diseases. Fitoterapia 2012;83(4):617-626. PubMed
  12. Hemingway, S. R. and Phillipson, J. D. Proceedings: Alkaloids from S. American species of Uncaria (Rubiaceae). J.Pharm.Pharmacol. 1974;26 Suppl:113P.
  13. Hilepo, J. N., Bellucci, A. G., and Mossey, R. T. Acute renal failure caused by 'cat's claw' herbal remedy in a patient with systemic lupus erythematosus. Nephron 1997;77(3):361. PubMed
  14. De Paula LCL, Fonseca F, Perazzo F, et al. Uncaria tomentosa (cat's claw) improves quality of life in patients with advanced solid tumors. J Altern Complement Med. 2015;21(1):22-30.
  15. Portalatin G, Shettigar S, Carrion-Rodriguez A, et al. Ketogenic-Diet Shake Containing Uncaria tomentosa-Associated Acute Interstitial Nephritis. Case Rep Nephrol Dial 2022;12(3):219-225.
  16. Lei S, Guo A, Lu J, et al. Activation of PXR causes drug interactions with Paxlovid in transgenic mice. Acta Pharm Sin B 2023;13(11):4502-4510. PubMed

See these in context on the Cat's Claw monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Supplement interaction checker › Check any supplement or product against your medications Drug–drug interactions › Check two or more of your medications against each other Browse medications A–Z › Every drug we've checked against herbs & supplements NDC & pricing lookup › Find a drug’s NDCs, packaging and costs Ask a pharmacist › Free, personal answer from our licensed team