Herb & supplement monograph

Blessed Thistle Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Blessed Thistle interacts with medications. The heart of this page is the interaction list — every drug Blessed Thistle is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Blessed Thistle is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Blessed Thistle Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Blessed Thistle drug interaction appears low for most people. Every interaction on record is rated minor, and none is backed by strong human evidence.

Interactions deserving the most attention

The one theme that stands out involves stomach acid. Blessed thistle has been reported to increase stomach acid, so it could theoretically work against medicines meant to reduce acid, including antacids, H2-blockers, and proton pump inhibitors (PPIs). Even here, the concern is based on limited reports rather than solid human studies, and the expected effect is mild. If your heartburn or reflux medicine seems less effective while taking blessed thistle, this could be one explanation worth discussing with us or your prescriber.

What the rest of the list means

Although a few dozen medications appear on the interaction list, that number mostly reflects how many individual acid-reducing products fall into these three groups, not many separate types of risk. All of these interactions are theoretical, and none has been shown to cause meaningful problems in people.

Check your medications against Blessed Thistle

Based on HelloPharmacist’s Blessed Thistle interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Blessed Thistle

36 medications have a known interaction with Blessed Thistle, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Blessed Thistle using our pharmacist-reviewed interaction data.

AI summaries are generated from our Blessed Thistle interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Blessed Thistle combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Blessed Thistle affects

Every type of medication (drug category) Blessed Thistle is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 3 drug categories Blessed Thistle interacts with

AntacidsH2-blockersProton Pump Inhibitors (ppis)

Antacids

Theoretically, blessed thistle might decrease the effectiveness of antacids.
There are reports that blessed thistle increases stomach acid.

Likelihood Possible Evidence D

H2-Blockers

Theoretically, blessed thistle might decrease the effectiveness of H2-blockers.
There are reports that blessed thistle increases stomach acid.

Likelihood Possible Evidence D

Proton Pump Inhibitors (Ppis)

Theoretically, blessed thistle might decrease the effectiveness of PPIs.
There are reports that blessed thistle increases stomach acid.

Likelihood Possible Evidence D

Monograph

Blessed Thistle: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Blessed thistle is a bitter herb traditionally used to stimulate appetite and ease mild digestive complaints. High-quality human studies are lacking, so its benefits are not well proven. It is likely fine for short-term use in small, food-like amounts, but it should be avoided in pregnancy and used with caution by people allergic to ragweed and related plants.

Scientific name: Cnicus benedictus
Family: Asteraceae
Part used: Aerial parts (leaves, stems, and flowers)
Common forms: Tea, tincture, liquid extract, capsules, dried herb

People commonly use it for

Digestive upset and poor appetite
Boosting bile flow
General bitter tonic
Supporting milk supply during breastfeeding (traditional)
Wound care (traditional, topical)

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Often well tolerated in small amounts, but human safety data are limited and large doses can cause nausea or vomiting.

PregnancyLikely Unsafe

When used orally; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Blessed thistle (Cnicus benedictus) is a spiny annual plant with yellow flowers that belongs to the daisy family (Asteraceae). It is native to the Mediterranean region and parts of Asia, and it now grows in many areas with mild climates, including parts of North America.

People have used blessed thistle in traditional herbal medicine for hundreds of years. It was once thought to be a cure-all and was popular during the Middle Ages. Today the dried aerial parts of the plant are most often taken as a bitter tea or tincture, or in capsules, mainly for digestive complaints and as a general tonic.

How it works

Blessed thistle contains bitter-tasting compounds, including a substance called cnicin, along with flavonoids, tannins, and small amounts of volatile oils. The bitter taste is thought to trigger reflexes that increase saliva and stomach acid, which may help with appetite and digestion.

Laboratory studies suggest that extracts of blessed thistle may have antibacterial and antioxidant activity. However, these findings come from test-tube and animal research. They do not prove that the herb produces the same effects in people, and they should not be taken as evidence that it treats infections or other conditions.

Effectiveness

Does Blessed Thistle work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 1 use evaluated

1 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Blessed Thistle, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 1 condition — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Dyspepsia

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral blessed thistle for dyspepsia, there is insufficient reliable information about the clinical effects of blessed thistle for this purpose.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

Blessed thistle is generally considered well tolerated when used in small, food-like amounts for a short time. Still, human safety data are limited, so caution is wise.

People who are allergic to ragweed, marigolds, daisies, chrysanthemums, or other plants in the Asteraceae family may also react to blessed thistle. Those with stomach or intestinal problems, such as ulcers, gastritis, or inflammatory bowel disease, should be careful because bitter herbs can increase stomach acid.

Pregnancy: Avoid blessed thistle during pregnancy. It has been associated with effects on the uterus in traditional use, and there is not enough safety information. Breastfeeding: It has been used traditionally to support milk supply, but its safety while nursing is not well studied, so talk to your doctor or pharmacist before using it. Always tell your healthcare provider about any supplement you take.

Side effects

When taken in normal amounts, blessed thistle usually causes few side effects. The most common problems are stomach-related.

Large doses can cause nausea, vomiting, and stomach irritation. Some people may have allergic reactions, especially if they are sensitive to related plants; these can include skin rash or itching. Stop using it and seek medical care if you have signs of a serious allergic reaction, such as swelling, trouble breathing, or a widespread rash.

Blessed Thistle: Reported Adverse Effects

Documented safety reports on Blessed Thistle from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Reports by condition

Dermatitis Dermatologic

Topically, blessed thistle can cause an allergic reaction, such as dermatitis, in individuals sensitive to the Asteraceae/Compositae family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many other herbs.

McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.

Nausea and vomiting Gastrointestinal

Orally, when blessed thistle is used in doses higher than 5 grams per cup of tea, it can cause stomach irritation and vomiting.

McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no official, standardized dose of blessed thistle. The right amount can vary depending on the product and the form (tea, tincture, or capsules).

The best approach is to follow the directions on the product label and not exceed the recommended amount, since large doses are more likely to cause nausea and vomiting. Because strengths differ from product to product, ask your pharmacist or doctor for guidance before starting, and use it only for short periods unless a healthcare professional advises otherwise.

Pregnancy & Breastfeeding

Blessed Thistle & Pregnancy

Likely Unsafe

When used orally; avoid using.

Blessed Thistle & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 2 references that drive our Blessed Thistle monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

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.

Brand directory

Brands that make products with Blessed Thistle

129 brands in our database make a supplement containing Blessed Thistle.

Advanced Naturals 68 products Advanced Nutrition by Zahler 135 products Advantage Pharmaceuticals 7 products Arthur Andrew Medical 36 products BEMORE 11 products Best Naturals 363 products Bio Nutrition 61 products Bioforce 26 products Biotech Corp. 1 product BodSmith 40 products Bust Bunny 2 products Century Systems 8 products Christopher's Original Formulas 140 products CRI Naturals Cellular Research Institute 3 products Crystal Star 123 products D'Adamo Personalized Nutrition 21 products DaVinci Laboratories 464 products DaVinci Laboratories Of Vermont 337 products DNA Dynamic Nutritional Associates 30 products Doctor Morse's Healing Herbs 47 products Dr. Christopher's Original Formulas 14 products Dr. Formulas 5 products Dr. Morse's Cellular Botanicals 79 products Dr. Seth's Vitamin Vibrations 37 products

Product directory

Supplement products with Blessed Thistle

731 products in our database contain Blessed Thistle. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Blessed Thistle: Common Questions

What is Blessed Thistle used for, and does it work?

People use Blessed Thistle for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does Blessed Thistle interact with prescription medications?

Yes. We list 36 medications with a known interaction with Blessed Thistle. Use the checker above to see how Blessed Thistle interacts with a specific drug.

How are Blessed Thistle interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Blessed Thistle with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Blessed Thistle interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Blessed Thistle used for?

It is mainly used in traditional herbal medicine to stimulate appetite and ease mild digestive complaints like bloating and indigestion. Strong scientific proof for these uses is lacking.

Is Blessed Thistle safe to take?

In small amounts for short periods it is generally well tolerated, but large doses can cause nausea and vomiting, and people allergic to ragweed or daisies may react to it. Check with a pharmacist or doctor first.

Can I take Blessed Thistle while pregnant or breastfeeding?

Avoid it during pregnancy because of possible effects on the uterus and a lack of safety data. While it has been used traditionally to support milk supply, its safety during breastfeeding is not well studied, so ask your doctor before using it.

How is Blessed Thistle usually taken?

It is most often taken as a bitter tea, a tincture, or in capsules. Because there is no standard dose, follow the product label and avoid taking large amounts.

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

Keep exploring

Products that contain Blessed Thistle

A rotating sample of real supplements in our database that list Blessed Thistle — open any to see its full ingredients and every drug interaction we check.

See all 731 products with Blessed Thistle →

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Blessed Thistle Drug Interactions, Uses, Effectiveness, Safety & More

Your Choice:

Blessed Thistle Drug Interactions: The Bottom Line

Drugs that interact with Blessed Thistle

Don’t want to scroll the list? Just ask.

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Likelihood — How Well It’s Documented

Where This Data Comes From

The kinds of drugs Blessed Thistle affects

Blessed Thistle: Uses, Safety & Side Effects

Overview

How it works

Does Blessed Thistle work?

Safety & precautions

Side effects

Blessed Thistle: Reported Adverse Effects

Dosing

Blessed Thistle & Pregnancy

Blessed Thistle & Breastfeeding

References & further reading

Brands that make products with Blessed Thistle

Supplement products with Blessed Thistle

Blessed Thistle: Common Questions

Related supplements & herbs

Products that contain Blessed Thistle

Have a question about Blessed Thistle?