Herb & supplement monograph

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

But these pages have grown well beyond that into a full monograph — what Calcium 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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Calcium 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 Calcium drug interaction is moderate for most people, mainly because calcium can bind to many medicines in the gut and lower how much gets absorbed. The great majority of listed interactions are moderate, a small handful are major, and most involve reduced absorption rather than a directly harmful effect.

Interactions deserving the most attention

The best-documented concerns involve levothyroxine and HIV medicines such as dolutegravir, where calcium can noticeably lower drug levels and weaken their effect. Calcium also reduces absorption of bisphosphonates, quinolone antibiotics, and tetracycline antibiotics. Combining calcium with thiazide diuretics can push blood calcium too high, which in rare cases affects the kidneys, and intravenous calcium given close to intravenous ceftriaxone is a serious concern in hospital settings.

What the rest of the list means

A long list of interactions does not mean every combination is harmful. Most entries reflect calcium physically binding to a medicine in the digestive tract, which lowers absorption but is manageable, and several concerns are theoretical or based on limited evidence. In some cases, such as with digoxin, predicted problems have not clearly shown up in human data.

Check your medications against Calcium

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

Interaction report

Drugs that interact with Calcium

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

7 major interactions. These combinations can be clinically significant — best avoided, or used only with close professional supervision. Always check with your pharmacist before combining them with Calcium.

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

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

AI summaries are generated from our Calcium 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 Calcium 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 Calcium affects

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

All 18 drug categories Calcium interacts with

Ceftriaxone (rocephin)Dolutegravir (tivicay)Elvitegravir (vitekta)AluminumBictegravir/emtricitabine/tenofovir Alafenamide (biktarvy)BisphosphonatesCalcipotriene (dovonex)Digoxin (lanoxin)Diltiazem (cardizem, Others)Levothyroxine (synthroid, Others)LithiumQuinolone AntibioticsRaltegravir (isentress)Sotalol (betapace)Tetracycline AntibioticsThiazide DiureticsVerapamil (calan, Others)Calcium Channel Blockers

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

Monograph

Calcium: Uses, Safety & Side Effects

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

The bottom line

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 calcium from food, and supplements should be used at the lowest dose needed. Talk to your pharmacist or doctor before starting, especially if you have kidney problems or take other medicines.

Part used: Mineral (not a plant part)
Common forms: Tablets, capsules, chewable tablets, liquids, powders; common salts include calcium carbonate and calcium citrate

People commonly use it for

Bone health and osteoporosis prevention
Dietary calcium deficiency
Heartburn relief (calcium carbonate antacids)
Supporting healthy teeth
High blood pressure support during pregnancy

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

Safety at a glance

OverallLikely safe

Generally safe when taken at recommended amounts, but high doses can cause problems.

PregnancyLikely Safe

When used orally and appropriately. The World Health Organization (WHO) recommends prescribing oral calcium supplementation 1.5-2 grams daily during p...

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally and appropriately. The World Health Organization (WHO) recommends prescribing oral calcium supplementation 1.5-2 grams daily during p...

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.

Jump to a section

Overview

Calcium is an essential mineral, meaning your body needs it but cannot make it on its own. You must get it from food or supplements. More than 99% of the calcium in your body is stored in your bones and teeth, where it gives them strength and structure. The small amount in your blood and tissues helps your nerves, muscles, heart, and blood clotting work properly.

Many foods are naturally rich in calcium, including dairy products like milk, cheese, and yogurt, as well as certain leafy green vegetables, canned fish with soft bones, and tofu. Many foods such as cereals, juices, and plant-based milks are also fortified with added calcium.

When diet is not enough, people often take calcium supplements. The two most common forms are calcium carbonate and calcium citrate. Carbonate contains more calcium per dose and is best taken with food, while citrate is absorbed well with or without food and may suit people with low stomach acid.

How it works

Calcium works mainly as a building block. In bone, it combines with phosphate to form a hard mineral called hydroxyapatite, which gives bones and teeth their strength. Your body constantly breaks down and rebuilds bone, and having enough calcium supports this process.

Beyond bones, calcium acts as a messenger inside and between cells. It helps nerves send signals, allows muscles (including the heart) to contract, supports the release of certain hormones, and is a key part of the blood clotting process.

Your body tightly controls the calcium level in your blood using hormones like parathyroid hormone and vitamin D. If you do not eat enough calcium, your body pulls it from your bones to keep blood levels steady, which over time can weaken bones.

Effectiveness

Does Calcium work?

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

Evidence overview · 53 uses evaluated

4 Effective 4 Likely effective 8 Possibly effective 4 Leans ineffective 3 Ineffective 30 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.

Effective Dyspepsia