Last update: June 11, 2024

Calcium: The Complete Guide

Learn all about calcium with our comprehensive guide, covering benefits, sources, supplements, and potential side effects. Dive into information on calcium to support your overall health.

Stephanie Wright

By Stephanie Wright, RN, BSN

Edited by Dr. Dimitar Marinov, MD, MBA, PhD

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Key takeaways

  • Calcium is an essential mineral for bones and teeth health, regulating muscle contractions, proper nerve function, and blood clotting.
  • The recommended daily intake of calcium varies by age and sex, ranging from 1,000 to 1,300 milligrams per day for adults.
  • Good sources of calcium include dairy products, leafy green vegetables, fish, and calcium-fortified foods.
  • Calcium deficiency can lead to osteoporosis. Other symptoms may include muscle cramps, numbness and tingling, and abnormal heart rhythms.

    What is calcium?

    Calcium is an essential mineral that plays a crucial role in maintaining overall health. As the most abundant mineral in the body, it serves as a primary component of bones and teeth, providing them with strength and structure. In addition to its skeletal functions, calcium is vital for muscle contraction, nerve transmission, and blood clotting [1].

    To meet the body's calcium needs, a balanced diet that includes calcium-rich sources is essential. Dairy products, such as milk, cheese, and yogurt, are excellent sources of calcium.

    For those who follow a plant-based diet or have lactose intolerance, leafy greens like spinach and kale, as well as fortified foods such as plant-based milk alternatives and cereals, can provide substantial amounts of calcium. By incorporating these foods into one's daily diet, individuals can ensure an adequate intake of this vital mineral, promoting overall health and well-being.

    Calcium is found everywhere

    Beyond biology, calcium compounds are widely used all around us. Calcium carbonate (CaCO3) appears in marble, limestone, and chalk, while calcium sulfate (CaSO4) is used to make plaster and drywall. Calcium is also used in cement and glass making!

    Can your body produce calcium?

    No. Your body can not produce calcium on its own, so it requires a steady supply of calcium from dietary sources or supplements. Adequate calcium intake is necessary for building and maintaining strong bones and teeth throughout life. It also ensures proper muscle function, facilitates efficient nerve communication, and aids in the blood clotting process [2].

    Different types of calcium

    Yes, there are different types of calcium compounds, each with its own unique chemical composition, properties, and applications. While calcium itself is a single element on the periodic table, it can be found in various forms and combinations with other substances. Here are the 6 most common types of calcium:

    1. Calcium Carbonate (CaCO3)
      The most common and cheapest form of calcium, often found in supplements and antacids. It has a high elemental calcium content (40%) but requires stomach acid for absorption, so it's best taken with food.
    2. Calcium Citrate (Ca3(C6H5O7)2)
      A more expensive form that is well absorbed even without stomach acid, making it suitable for people with low stomach acid levels or those taking acid-blocking medications. It has a lower elemental calcium content (21%) than calcium carbonate.
    3. Calcium Phosphate (Ca3(PO4)2)
      Found naturally in bones and teeth, and also used in some supplements. It has a high elemental calcium content (38-40%) and is well absorbed, but less common in supplements compared to carbonate and citrate forms.
    4. Calcium Lactate (C6H10CaO6)
      A form with a lower elemental calcium content (13%) that is easily absorbed but less frequently used in supplements due to the larger volume needed to achieve the same amount of calcium as other forms.
    5. Calcium Gluconate (C12H22CaO14)
      Another form with a low elemental calcium content (9%), sometimes used in supplements and food additives. It is well absorbed but requires a larger volume to provide the same amount of calcium as other forms.
    6. Calcium Hydroxyapatite (Ca5(PO4)3OH)
      A natural form of calcium found in bones and teeth, and also available in supplements. It contains a mix of calcium and phosphorus and has an elemental calcium content of approximately 40%. Some studies suggest it may be more effective for bone health than other forms of calcium.

    How does calcium work in your body?

    What are some benefits of calcium?

    Calcium is essential for maintaining good health. Here are a few benefits of maintaining sufficient calcium in your diet.

    1. Contributes to bone health

      Your body needs calcium for strong bones, which is crucial for groups at risk, like postmenopausal women and the elderly. Studies on calcium supplements and osteoporosis vary, but ensuring enough calcium, vitamin D, and weight resistance exercise lowers the risk of bone issues later in life [3].

    2. Supports blood clotting

      Calcium is critical in your blood's ability to clot, contributing to the complex coagulation process. This ensures proper wound healing and prevents excessive bleeding, highlighting the importance of maintaining proper calcium levels for overall circulatory health [4].

    3. Helps blood pressure regulation

      Enough calcium is associated with maintaining normal blood pressure levels, and some studies suggest a correlation between lower calcium intake and an increased risk of hypertension and stroke [5].

    4. Supports preeclampsia prevention

      If pregnant women don't get enough calcium, taking extra calcium supplements can help lower the chance of preeclampsia. Preeclampsia is when a pregnant woman has high blood pressure and damage to her organs. Pregnant women must make sure they have enough calcium [6].

    5. Improves cholesterol levels

      Calcium is recognized for its positive effect on certain cholesterol levels in the blood, contributing to overall cardiovascular health. Including calcium-rich foods in your diet can be a part of a heart-healthy lifestyle [7].

    What are some signs of calcium deficiency?

    When your body is running low on calcium, it will attempt to maintain stable calcium levels in the bloodstream due to its crucial importance for the heart, nervous system, clotting, etc. Therefore, it will start drawing calcium out of its main storage - in the bones and teeth. Consequently, signs of calcium deficiency usually develop slowly over time and include [1, 2]:

    • Reduced Bone Density: Losing calcium from bones leads to reduced bone mineral density and increased risk of fractures - due to osteoporosis and osteomalacia.
    • Reduced Teeth Mineralization: This increases the risk of dental problems such as dental caries.
    • Other Serious Symptoms: Severe calcium deficiency and some conditions that affect calcium metabolism can lead to low serum calcium levels and symptoms such as muscle cramps and spasms, neurological problems (confusion, depression), and other serious symptoms.

    Never self-diagnose

    If you feel you may have a deficiency or are concerned or curious about taking this supplement, talk to a doctor or healthcare professional. They can accurately diagnose and recommend the appropriate treatment plan for your specific needs.

    Sources of calcium

    Calcium can be obtained from various sources, primarily from foods but also from supplements when dietary intake is insufficient.

    Calcium-rich foods

    Below is a categorization of various foods based on their calcium content, helping you to identify sources that can boost your dietary calcium intake.

    Is food intake always the best?

    Obtaining calcium from food is generally recommended. However, in cases of significant deficiency, dietary restrictions, or certain health conditions, supplements may be necessary.

    Calcium supplement formulations

    Calcium can be present in various compounds and supplement formulations, each with its own unique properties and applications. Here are some of the most popular [1, 2]:

    1. Calcium-Magnesium (Cal-Mag): These supplements provide a combination of calcium and magnesium, two essential minerals that work together to support bone health, muscle function, and other bodily processes. The most common forms are calcium carbonate or citrate combined with magnesium oxide or citrate.
    2. Calcium + Vitamin D: Many calcium supplements also include vitamin D, as it helps improve calcium absorption and supports bone health. Vitamin D3 (cholecalciferol) is the preferred form due to its better bioavailability.
    3. Calcium + Vitamin K2: Some newer calcium supplement formulations include vitamin K2, particularly in the form of menaquinone-7 (MK-7). Vitamin K2 helps direct calcium to the bones and teeth, reducing the risk of calcification in soft tissues like blood vessels.
    4. Plant-Based Calcium: Some calcium supplements are derived from plant sources, such as algae (e.g., Algaecal) or red marine algae (Aquamin). These forms often contain additional trace minerals that may support bone health.

    Delivery methods

    Calcium supplements come in various delivery methods, each offering its own set of benefits and forms of consumption. Here's a brief overview of the different delivery methods:

    Choose a method that fits your routine

    Do not overlook the delivery method. Calcium supplements come in tablets, capsules, soft gel, chewable, powders, and liquid forms—choose the one that best fits your daily routine to stay consistent.

    What to look for in calcium supplements

    When selecting a supplement, several key factors must be considered to ensure you choose a high-quality product that effectively supports your health goals and overall well-being.

    • Dosage and potency

      The dosage of calcium in supplements varies, so it's important to choose one that aligns with your specific needs. This includes considering your age, gender, and health status, like pregnancy or existing deficiencies. The calcium formulation can impact its potency and bioavailability, which affects how effectively your body can absorb and use it.

    • Quantity and delivery method

      The delivery method is crucial. Calcium supplements come in various forms, including tablets, capsules, powders, chewables, and liquid forms. Your choice may depend on factors like ease of swallowing, convenience for traveling, or personal preference regarding taste and texture. Also, evaluate the quantity of calcium to determine how long it will last based on your daily requirements.

    • Quality and manufacturing

      Quality is paramount when selecting calcium supplements. Look for products manufactured under strict quality control guidelines and those that have undergone third-party testing for purity and label accuracy. Certifications from recognized bodies can be a reliable indicator of a high-quality product. Additionally, consider the manufacturer's reputation and transparency in their production processes.


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    How and when should you take calcium for maximum absorption?

    To get the most out of your calcium supplement, it's crucial to consider the timing and method of consumption. The following dos and don'ts offer guidance on optimizing absorption, efficiently supporting your health and wellness, and minimizing potential discomfort.


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      To enhance bone health, incorporate calcium-rich foods into your meals. This optimizes calcium absorption, as stomach acid, which aids in this process, is produced during eating.

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      Consume calcium in divided doses, preferably 500 mg or less at a time, for effective absorption throughout the day.

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      Ensure sufficient vitamin D intake, as calcium cannot be absorbed without it.


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      Don't take calcium pills when your stomach is empty; it won't absorb well.

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      Also, don't take calcium and iron pills together, as they can affect how your body absorbs them.

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      Keep your calcium pill doses to 500 mg or less because your body doesn't take in as much when you have more.

    Who should take calcium?

    Taking calcium supplements has its potential benefits, but it may not be for everyone.

    Recommended dosage

    Calcium plays an important role in many physiological processes, and getting the right dosage is essential for maintaining optimal health at different life stages. Here are the recommended dosages for calcium across various age groups.

    Side effects of excessive calcium consumption

    While calcium supplements are generally safe when taken within recommended limits, excessive intake can have adverse effects:

    • Kidney Issues: High calcium can contribute to kidney problems, including the formation of kidney stones.
    • Low Phosphate Levels: An imbalance in calcium-phosphate ratios may result in low phosphate levels, impacting bone health.
    • Excessive Urination: Overconsumption may increase urine production, affecting fluid balance.
    • Nausea and Fatigue: Hypercalcemia might induce feelings of nausea and persistent fatigue.

    Always consult your doctor

    If you're experiencing side effects, consult your healthcare provider. They may recommend a different calcium formulation or adjust your dosage. Balancing your calcium needs with any discomfort is crucial and should not be overlooked.

    Health made easy: your go-to resource for essential vitamins and supplements

    Frequently asked questions about calcium (FAQ)

    Our library of expert-authored articles covers just about every question you might have about vitamins, minerals, and supplements — along with some you might not have known you had.

    Final thoughts

    Calcium is important for keeping your bones healthy and supporting your overall health. It's critical for people of all ages to get enough calcium, whether from food or supplements. Listen to advice from your doctor to find the right balance to ensure you get enough calcium without going overboard.

    Sources and references

    1. Calcium - Health Professional Fact Sheet
    2. Calcium | The Nutrition Source | Harvard T.H. Chan School of Public Health
    3. Nutrition and osteoporosis prevention and treatment | Biomedical Research and Therapy
    4. The Role of Calcium in Wound Healing
    5. Dietary Calcium Intake and Hypertension: Importance of Serum Concentrations of 25-Hydroxyvitamin D - PMC
    6. Calcium for pre‐eclampsia prevention: A systematic review and network meta‐analysis to guide personalised antenatal care - Woo Kinshella - 2022 - BJOG: An International Journal of Obstetrics & Gynaecology - Wiley Online Library
    7. Calcium Intake and Risk of Cardiovascular Disease: A Review of Prospective Studies and Randomized Clinical Trials - PMC
    8. Food Sources of Calcium | Dietary Guidelines for Americans
    9. Hypercalcemia - StatPearls - NCBI Bookshelf
    10. Lower Serum Calcium Levels Associated with Disrupted Sleep and Rest-Activity Rhythm in Shift Workers


    Stephanie Wright avatar

    Stephanie brings over 13 years of diverse nursing experience to the table, having honed her expertise in critical care, mental health, and utilization management. Her journey as a registered nurse across these various healthcare sectors underscores her adaptability and deep commitment to patient care.

    Fact checker

    Dr. Dimitar Marinov avatar

    Dr. Marinov has years of experience in scientific research and preventive and clinical medicine. His publications in peer-reviewed journals are on nutritional status, physical activity, and musculoskeletal disorders among adolescents.

    At VitaRx, we're not just passionate about our work — we take immense pride in it. Our dedicated team of writers diligently follows strict editorial standards, ensuring that every piece of content we publish is accurate, current, and highly valuable. We don't just strive for quality; we aim for excellence.

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    Get your personalized vitamin recommendations in less than 3 minutes.

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