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mineral

Calcium

Evidence: High · 100%
Chemical structure of Calcium (PubChem CID 5460341)
Structure via PubChem
Half-life
—
Typical timing
with_meal
Food rule
with food
Default unit
mg

Studied for

Longevity

Overview

Calcium is an essential mineral naturally present in many foods, added to others, present in some medicines (such as antacids), and available as a dietary supplement. It is the most abundant mineral in the body (NIH ODS). Approximately 99% of the body's calcium is stored in the bones and teeth, providing structural support and acting as a reservoir to maintain constant calcium concentrations in the blood, muscle, and intracellular fluid (NIH ODS). The remaining 1% of the body's calcium is involved in vital functions such as vascular contraction and vasodilation, muscle function, nerve transmission, intracellular signaling, and hormonal secretion (NIH ODS). Sufficient calcium intake is crucial throughout life for building and maintaining strong bones and promoting overall health. The body maintains very tight control over the level of calcium in the blood. If blood calcium levels drop too low, the parathyroid glands release parathyroid hormone (PTH), which signals bones to release calcium into the blood, kidneys to reabsorb calcium, and intestines to increase calcium absorption (NIH ODS). Adequate vitamin D is essential for calcium absorption in the gut. The recommended dietary allowance (RDA) for calcium varies by age and sex, typically ranging from 1,000 mg to 1,300 mg per day for adults (NIH ODS).

Deep dive

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Known interactions

  • Compound-pair rule
    Caution

    Calcium competes with iron for absorption, so taking large doses together reduces iron uptake.

    Separate them by at least 2 hours.

    Suggested separation: 2 h

  • Compound-pair rule
    Caution

    High-dose calcium can reduce zinc absorption taken at the same time.

    Separate by 2 hours if both are high-dose.

    Suggested separation: 2 h

  • Compound-pair rule
    Note

    Very large simultaneous doses can compete for absorption.

    If both high-dose, splitting them can help.

  • Compound-pair rule
    Caution

    Calcium reduces absorption of thyroid medication when taken together.

    Separate by about 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Divalent cations chelate levothyroxine in the gut and reduce absorption by up to 30%.

    Take levothyroxine on empty stomach; separate mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Divalent cations chelate levothyroxine in the gut and reduce absorption by up to 30%.

    Take levothyroxine on empty stomach; separate mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Minerals chelate T3 and reduce absorption.

    Separate liothyronine and mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Calcium competes with iron for absorption.

    Separate iron and calcium by at least 2 hours.

    Suggested separation: 2 h

  • Compound-pair rule
    Caution

    Divalent cations chelate levothyroxine in the gut and reduce absorption by up to 30%.

    Take levothyroxine on empty stomach; separate mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Divalent cations chelate levothyroxine in the gut and reduce absorption by up to 30%.

    Take levothyroxine on empty stomach; separate mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Minerals chelate T3 and reduce absorption.

    Separate liothyronine and mineral supplements by at least 4 hours.

    Suggested separation: 4 h

  • Compound-pair rule
    Caution

    Calcium competes with iron for absorption.

    Separate iron and calcium by at least 2 hours.

    Suggested separation: 2 h

Frequently asked

Sources referenced

- British Medical Journal (BMJ) - Cochrane Library - DrugBank - European Medicines Agency (EMA) SmPC - Food and Drug Administration (FDA) - Mayo Clinic - MedlinePlus - National Institutes of Health (NIH) Office of Dietary Supplements (ODS) - U.S. Preventive Services Task Force (USPSTF)

DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician.

Cite this page

Using this in an article, AI answer, or research note? Please attribute:

DoseRoutine. (2026). Calcium — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/calcium
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