Drug & supplement interaction

Blessed Thistle + Calcium Carbonate

Calcium Carbonate brand names: Tums, Os-Cal, Adcal, Calcichew, Adcal-D3.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Blessed Thistle has a minor interaction with Calcium Carbonate. Theoretically, blessed thistle might decrease the effectiveness of antacids.

Read the full interaction report
SeverityMinor
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Blessed Thistle and Calcium Carbonate

Here is the interaction we found between these two, with the evidence behind it.

Minor

ANTACIDS

Why this applies to Calcium Carbonate

Calcium Carbonate falls under ANTACIDS — the group Blessed Thistle interacts with.

Theoretically, blessed thistle might decrease the effectiveness of antacids.
There are reports that blessed thistle increases stomach acid.
Severity Minor Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version. Calcium carbonate (Tums and similar) works as an antacid by neutralizing stomach acid, which is what calms that burning, sour feeling. Blessed thistle, on the other hand, is a bitter herb that may gently boost stomach acid as part of how it stirs up appetite and digestion. So in theory, the two could work against each other, and your Tums might not relieve heartburn quite as well as usual.

I want to be honest about how shaky this is. It's based on anecdotal reports, not solid studies, and the effect is rated minor. Small, food-like amounts of the herb likely won't matter much. If you find your antacid isn't doing its job while using blessed thistle, just check in with your pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Blessed Thistle Also Interacts With Other Medications

Blessed Thistle has 35 minor known drug interactions in our database — the Calcium Carbonate one above is one of them. If you take anything else, check it against the full list below.

Minor 35 No known interaction 2,795 (incl. Calcium Carbonate)
Taking anything else?

Check Another of Your Medications Against Blessed Thistle

Covers the 2,830 medications we’ve checked against Blessed Thistle. Pick one to open its full report.

From our Q&A

Questions About Blessed Thistle or Calcium Carbonate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Blessed Thistle or Calcium Carbonate, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Calcium Carbonate

This page covers Blessed Thistle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Calcium Carbonate page lists 30 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Cinchona (moderate), Coffee Charcoal (moderate), European Mandrake (moderate) and Glucomannan (moderate).

By severity: 1 major · 10 moderate · 19 minor.

From our pharmacist’s overview on the Calcium Carbonate page

“Calcium carbonate (Tums, Os-Cal) feels like the most harmless thing in the medicine cabinet, which is exactly why its supplement list deserves a careful read, led by activated charcoal, the single major-rated entry. Charcoal adsorbs many medicines in the gut and can strip away their effect, and it does not spare oral drugs taken alongs…”

Reviewed by 2 · Jul 18, 2026

Open the Calcium Carbonate interaction page

One more smart check

Taking Blessed Thistle as Part of a Dietary Supplement Product? Check It for Interactions

We hold 729 real supplement products containing Blessed Thistle, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Blessed Thistle. Your product may carry other ingredients that interact with Calcium Carbonate too, on top of Blessed Thistle — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Blessed Thistle and Calcium Carbonate Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Blessed Thistle
Top 25%

#311 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Calcium Carbonate
Top 10%

#208 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Blessed Thistle

What is Blessed Thistle?

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

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.

Read the full Blessed Thistle monograph & all interactions
Medication

About Calcium Carbonate

What Is Calcium Carbonate Used For?

Brand names: Tums, Os-Cal, Adcal, Calcichew, Adcal-D3

Most calcium carbonate products are used as an antacid — they quickly relieve heartburn, acid indigestion, sour stomach, and upset stomach. This covers a wide range of brands including Tums, Rolaids, CAREONE Extra Strength, Calcium Carbonate Chewable Antacid, exchange select Extra Strength Antacid, Extra Strength Smooth, and the Children's Antacid and Children's Stomach Relief Antacid liquids.

Some products go beyond antacid use. Ki No Sin (capsule) is used as a health supplement to aid body functions affected by diabetes and kidney disease, and to help maintain normal calcium levels. Na Mi Cal is a supplement intended to support healthy bone development and help prevent osteoporosis. TC Max oral solution is indicated for the relief of heartburn, acid indigestion, sour stomach, and upset stomach.

See full Calcium Carbonate drug information
Keep checking

Other Drugs & Blessed Thistle

Browse every other medication we’ve checked against Blessed Thistle — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
35Minor
2,794No known interaction
35 Minor 2,794 No interaction
Minor

35 interactions

No interaction 2,794 drugs checked — show the list

We also checked Blessed Thistle against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,794 medications checked with no known interaction — see the full Blessed Thistle list.

See the full Blessed Thistle interactions page
See every supplement checked against Calcium Carbonate, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

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

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
Blessed Thistle monograph › Uses, safety, and every drug interaction in one place Calcium Carbonate supplement interactions › Every supplement checked against Calcium Carbonate, ranked by severity Calcium Carbonate drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Blessed Thistle and Calcium Carbonate Together: Common Questions

Can you take Blessed Thistle with Calcium Carbonate?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Blessed Thistle and Calcium Carbonate interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Calcium Carbonate and Blessed Thistle?

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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.