Drug & supplement interaction

Strontium + Calcium Carbonate

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

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

Strontium has a moderate interaction with Calcium Carbonate. Antacids can reduce the absorption of strontium, potentially decreasing its effectiveness.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceC
What do Severity, Likelihood & Evidence mean?
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Interaction report

Strontium and Calcium Carbonate

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

Moderate

ANTACIDS

Why this applies to Calcium Carbonate

Calcium Carbonate falls under ANTACIDS — the group Strontium interacts with.

Antacids can reduce the absorption of strontium, potentially decreasing its effectiveness.
Aluminum hydroxide and magnesium hydroxide can reduce absorption of strontium ranelate by 20% to 25%. Calcium can reduce its absorption to 60% to 70%. Avoid taking antacids within 2 hours of a dose of strontium ranelate. This interaction has also been reported with orally-administered radioactive strontium-85. It will likely also occur with other forms of strontium.
Severity Moderate Likelihood Probable Evidence C

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..

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

Here's the simple version: calcium and strontium are chemical cousins, so your body uses similar pathways to absorb them. When you swallow calcium carbonate (think Tums or Os-Cal) too close to a strontium dose, the calcium basically wins the competition for absorption. Studies show this can cut how much strontium gets into your system by quite a lot, in the range of 30 to 40 percent, which means your strontium may simply not work as well for bone support.

The fix is easy and doesn't require stopping anything: just space them out. A common suggestion is to keep your antacid or calcium dose at least 2 hours away from strontium. This isn't a dangerous reaction, it's mostly about getting your money's worth from the strontium. Run your timing plan by your pharmacist to be sure it fits everything else you take.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Protelos European Summary of Product Characteristics. Les Laboratoires Servier, 2006. Available at: www.servier.com/pro/osteoporose/protelos/protelos_spc.asp. (Accessed 01 August 2006).
  2. US Department of Health and Human Services, Public Health Service. Agency for Toxic Substances and Disease Registry. Toxicological profile for strontium. April 2004. Available at: www.atsdr.cdc.gov/toxprofiles/tp159.pdf. (Accessed 8 August 2006).
  3. Rousselet F, El Solh N, Maurat JP, et al. Strontium and calcium metabolism. Interaction of strontium and vitamin D. C R Seances Soc Biol Fil 1975;169:322-9.

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

Strontium Also Interacts With Other Medications

Strontium has 100 moderate 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.

Moderate 100 No known interaction 2,730 (incl. Calcium Carbonate)
Taking anything else?

Check Another of Your Medications Against Strontium

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

From our Q&A

Questions About Strontium 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 Strontium 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 Strontium 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 Strontium as Part of a Dietary Supplement Product? Check It for Interactions

We hold 347 real supplement products containing Strontium, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Strontium. Your product may carry other ingredients that interact with Calcium Carbonate too, on top of Strontium — 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 Strontium 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 Strontium
Top 25%

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

29 days ago today
Medication Calcium Carbonate
Top 25%

#636 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 Strontium

What is Strontium?

  • Bone health and osteoporosis
  • Reducing fracture risk
  • Tooth sensitivity (in some toothpastes)
  • Supporting bone density

Strontium is a mineral that has been studied mainly for bone health and osteoporosis. The prescription form (strontium ranelate) showed benefit for fracture risk but carries serious heart-related safety concerns, while the over-the-counter supplement form (strontium citrate) has much less evidence. Talk to your doctor or pharmacist before using it, especially if you have heart disease or are at risk for blood clots.

Read the full Strontium 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 here are antacids. They relieve heartburn, acid indigestion, sour stomach and upset stomach linked to those symptoms.

A few supplement products have different uses. Na Mi Cal is intended to support bone development and maintenance in adolescents and adults, and may help prevent osteoporosis. Ki No Sin is a health supplement used to help with body functions affected by diabetes and kidney disease, and to help maintain normal calcium ion levels. R Cos is a dietary supplement meant to support the immune system.

See full Calcium Carbonate drug information
Keep checking

Other Drugs & Strontium

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

0Major
100Moderate
0Minor
2,729No known interaction
100 Moderate 2,729 No interaction
Moderate

100 interactions

Showing 60 of 100 moderate interactions — see all 100 on the Strontium page.

No interaction 2,729 drugs checked — show the list

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

Showing the 60 most looked-up of 2,729 medications checked with no known interaction — see the full Strontium list.

See the full Strontium 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
Strontium 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 Strontium and Calcium Carbonate Together: Common Questions

Can you take Strontium with Calcium Carbonate?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Strontium and Calcium Carbonate interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Calcium Carbonate and Strontium?

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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.