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    Calcium Citrate

    Also known as: Ca citrate

    Calcium bound to citric acid; ~24% elemental Ca by mass; absorbed across the small intestine via active transport and paracellular diffusion regardless of gastric pH.

    Last reviewed: 2026-06-23 · 1 indexed study

    Evidence Score
    75/100
    Calcium repletionBone healthAcid-independent absorptionPost-bariatric supplementation
    Data Completeness3/4 · 75%
    Evidence ScoreDosageSafetyLinked Studies

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    Overview

    Calcium citrate is a well-absorbed calcium salt that does not require gastric acid for absorption, making it suitable for older adults, PPI users, and post-bariatric patients.

    Mechanism & Function

    Mechanism of Action

    Replenishes serum and bone calcium pools, supports osteoblast function, neuromuscular signalling, and clotting cascade.

    Physiological Role

    Supports bone mineral density in athletes with high sweat losses or restricted dairy intake; reduces fracture risk in older masters athletes.

    Primary Pathways

    Active intestinal Ca²⁺ transportBone mineralisationNeuromuscular signallingClotting cascade

    Performance / Health Relevance

    Absorbed equally well with or without food, unlike calcium carbonate; preferred form in achlorhydric or PPI-using individuals.

    Evidence Review

    Overall75/100
    Human Clinical82/100
    Meta-AnalysisN/A

    No meta-analyses or systematic reviews indexed for this ingredient yet.

    Mechanistic88/100
    Real-World72/100
    Safety88/100

    Dimensions marked N/A have no indexed evidence of that class. They are shown as unavailable rather than scored.

    Compare Calcium Forms

    7 calcium forms are indexed. Bioavailability, clinical evidence, and best-use cases differ meaningfully between them.

    FormEvidence
    Calcium CitrateThis page

    ~22–27% absorption regardless of stomach acidity.

    75/100
    Calcium Caseinate

    DIAAS ≈ 1.18; complete EAA profile.

    78/100
    HMB

    Ca-HMB ~80%; HMB-FA produces 2× higher peak plasma at same dose.

    68/100
    Calcium Carbonate

    Calcium carbonate provides elemental calcium but requires gastric acid for absorption; absorption may be reduced on a completely achlorhydric stomach.

    67/100
    Vitamin B5 (Pantothenic Acid)

    Well-absorbed from the gastrointestinal tract. Bioavailability is generally high.

    65/100
    Calcium AKG

    Moderate.

    48/100
    Calcium Lactate

    One trial measured absorption from a calcium lactate drink; small differences in fractional absorption were observed when additional caseinophosphopeptide preparations were included, but these differences were judged unlikely to be biologically meaningful.

    45/100
    Open full side-by-side comparison

    Practical Use & Dosage

    Minimum Effective Dose
    500 mg elemental Ca/day
    Optimal Range
    500–1000 mg/day in divided doses
    Upper / Caution Level
    2500 mg/day total intake
    Timing
    With or between meals; split if >500 mg
    Best Format
    Tablet, powder, chewable
    Bioavailability
    ~22–27% absorption regardless of stomach acidity.
    Absorption Considerations
    Single doses >500 mg show diminishing absorption — split for optimal uptake.

    Safety & Interactions

    Side Effects

    • •Constipation
    • •Mild bloating

    Contraindications

    • Hypercalcaemia
    • Severe kidney disease

    Drug Interactions

    • •Tetracyclines
    • •Levothyroxine
    • •Bisphosphonates
    • •Quinolones

    Who Should Avoid

    • •Hyperparathyroidism without monitoring

    Monitoring

    Serum Ca in renal patients.

    Frequently Asked Questions

    Auto-generated from indexed evidence — dosage, safety, interactions, and more.

    When is Calcium Citrate typically used or indicated?

    Calcium Citrate is most commonly used for: Calcium repletion, Bone health, Acid-independent absorption, Post-bariatric supplementation. Supports bone mineral density in athletes with high sweat losses or restricted dairy intake; reduces fracture risk in older masters athletes.

    How does Calcium Citrate work?

    Replenishes serum and bone calcium pools, supports osteoblast function, neuromuscular signalling, and clotting cascade.

    What is the recommended dose of Calcium Citrate?

    The optimal range is 500–1000 mg/day in divided doses. with a minimum effective dose of 500 mg elemental Ca/day. Best taken: With or between meals; split if >500 mg. Upper / caution level: 2500 mg/day total intake.

    What are the side effects of Calcium Citrate?

    Reported side effects include: Constipation; and Mild bloating. Monitoring: Serum Ca in renal patients.

    Does Calcium Citrate interact with medications?

    Known or theoretical interactions: Tetracyclines; Levothyroxine; Bisphosphonates; and Quinolones. Always check with a clinician before combining with prescription medication.

    Who should avoid Calcium Citrate?

    Calcium Citrate is generally not recommended for: Hyperparathyroidism without monitoring; Hypercalcaemia; and Severe kidney disease.

    How strong is the evidence for Calcium Citrate?

    Evidence level: Strong (overall score 75/100), based on 1 indexed study on SuppIndex.

    Research & References (1)

    Calcium citrate vs calcium carbonate absorption

    RCT1999Strong
    PubMed

    Citrate showed 22–27% better absorption, especially in fasted state.

    Related Ingredients

    Other top-rated ingredients in Minerals.

    Magnesium Glycinate

    84/100

    An amino acid chelate of magnesium providing elemental Mg²⁺ bound to two glycine molecules, offering superior bioavailability and minimal gastrointestinal side effects.

    Zinc

    74/100

    Systematic reviews and meta-analyses of human trials show that oral zinc supplementation reduces duration and increases recovery rates in acute and persistent watery diarrhoea in children; lowers inflammatory lesion counts in acne; reduces pain severity in primary dysmenorrhea; and in small trials (20–30 mg/day) improved fasting glucose and 2‑hr OGTT in people with prediabetes. Adverse effects reported include increased vomiting in children receiving zinc for diarrhoea.

    Magnesium Citrate

    70/100

    Magnesium ion bound to citric acid; citrate enhances solubility and intestinal absorption while providing mild osmotic laxative effect at higher doses.

    Research Overview

    Strong Evidence
    1Total Studies
    1Human Trials
    0Meta-Analyses
    1999Latest Study
    0Animal / In Vitro
    0Athlete Studies
    Primary data sourceGeneral Population
    Pooled evidence (meta-analysis / systematic review)No

    Cite this ingredient

    One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.

    Stable URL

    https://thesuppindex.com/ingredients/calcium-citrate

    SuppIndex. (2026). Calcium Citrate: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/calcium-citrate

    Based on 1 indexed studies · Evidence level: Strong.

    Goal Ratings

    General Health
    Recovery

    Stack Compatibility

    Combine with vitamin D3, K2, and magnesium for bone matrix support.

    Vitamin D3Vitamin K2Magnesium