Benefits, Side Effects, Dosage, Interactions

Calcium is an essential nutrient found in dairy products, dark-green leafy vegetables, legumes, and fortified foods.  The most abundant mineral in the body, 99{7b6cc35713332e03d34197859d8d439e4802eb556451407ffda280a51e3c41ac} of calcium is stored in the bones and teeth. Calcium is also important for circulation, hormones, muscle, and nerve health.

As we age, calcium levels naturally decline. For this reason, many people take calcium supplements to prevent osteoporosis. Calcium carbonate (calcite) and calcium citrate (Citracal) are the two most popular forms of calcium supplements.

This article discusses calcium. It explains the health benefits, recommended daily intakes, and potential side effects of calcium supplements.

Verywell / JR Bee

Calcium Health Benefits

Calcium plays a key role in quite a few of your body’s functions. They include calcium’s ability to:

  • Help form bones and teeth
  • Help maintain body strength
  • Assist in the movement of muscles
  • Assist with nerve messaging between the brain and body systems
  • Help blood flow as vessels relax and constrict
  • Release hormones and enzymes that support body functions

Bone density continues to build during the first 25 to 30 years of life. It then slowly decreases with age. More calcium is needed during times of growth in the adolescent and young adult years. People need enough calcium in their youth to achieve peak levels of bone mass and limit bone loss later on.

Bone breakdown is greater than bone formation in your later years. This is especially true in women after menopause when bone loss can lead to fractures and osteoporosis. This is another time calcium intake should increase in the body.

Bone Density and Osteoporosis

Your body needs calcium to build bone and prevent or delay bone loss later in life. This is especially important for the people most at risk for bone loss, including women after menopause and the elderly.

Osteoporosis is a bone disorder characterized by porous and fragile bones. It is associated with bone fractures. Many studies have looked at the role of calcium supplements and osteoporosis.

Some research studies have shown that calcium supplements have a protective effect on certain fractures. Others do not. The outcomes vary based on the groups of people studied, their age, and how well (or not) they maintained their consistent use of calcium supplements.

One thing that is certain is that having adequate levels of calcium and vitamin D in your diet and weight resistance exercise may reduce the risk of osteoporosis later in life.


Calcium plays a key role in maintaining your body’s health for quite a few reasons, but bone health is perhaps the most important. Getting the right amount of calcium when you’re young helps to prevent bone loss in your later years.

Colon Cancer

There is a lot of data to suggest calcium may help to prevent colon cancer. However, it’s important to remember these results remain inconclusive.

One review, for example, assessed the effects of calcium supplements on the development of colon cancer. It looked specifically at adenomatous polyps, the growths that may be precursors to cancer.

Researchers found that calcium supplements may contribute to a moderate level of protection from these polyps. However, the data was not strong enough to support a recommendation for their use in preventing colon cancer.

On the other hand, one Harvard study looked at higher calcium doses of 1,250 milligrams (mg) per day. The results suggested a 35{7b6cc35713332e03d34197859d8d439e4802eb556451407ffda280a51e3c41ac} reduction in some colon cancers with the higher doses. This may mean the amount of calcium and the population that takes it are factors in the level of protection calcium can provide for colon health.

Many other factors beyond calcium contribute to the risk of colon cancer, though. They include:

  • Genetics
  • Weight
  • Diet
  • Smoking

Weight Control

The research results are mixed on how calcium may help with weight control, too. Some studies have shown a link between high calcium intake and lower body weight. Others further show that eating foods rich in low-fat calcium within a diet that limits your total calories may reduce your risk of obesity. It may also increase weight loss in obese people.

A 2012 study published in the American Journal of Clinical Nutrition suggests that calcium does not have weight control effects unless total calories are restricted. In addition, calcium supplements (as opposed to calcium in your diet) did not seem to provide the same benefits.

If you are looking to lose weight, the most important thing is to make sure you are using more calories than you are taking in. Diets should always be well-balanced and full of vegetables, fruit, whole grains, lean protein, and healthy fats.

If you are thinking of adding more dairy to your diet, keep in mind that whole fat dairy can be high in calories and saturated fat. Adding dairy without cutting calories could cause weight gain.


Preeclampsia is a condition that occurs in pregnant women. The symptoms include:

  • High blood pressure
  • Swelling of the hands and feet
  • Protein in the urine

Researchers have looked at the potential benefits of calcium supplements in preventing preeclampsia. One review analysis of 13 clinical trials found that taking 1,000mg per day of calcium, beginning at about 20 weeks gestation, did show a significant reduction in the risk of high blood pressure, preeclampsia, and premature births. 

High Blood Pressure

The verdict on whether calcium reduces blood pressure or the risk of high blood pressure is mixed. Some clinical trials have found a relationship between calcium intake and hypertension risk, while others have found no association.

Small changes in systolic blood pressure have been noted, but the type of effect may depend on the population being studied.

Heart Disease

The research on calcium and heart disease is complicated. There seems to be no direct link between the calcium you get from your diet and the amount in your arteries (a sign of early heart disease). Yet some research has found a link between the use of calcium supplements and cardiovascular (heart) disease, or CVD.

One theory is that calcium supplements have a greater effect on calcium levels in the blood. This increases what is called calcification, a marker for CVD. High calcium levels are linked to increases in blood coagulation, which can cause clotting and related conditions that raise your risk of CVD.

Researchers found that calcium supplements, with or without vitamin D, modestly increase the risk of a heart attack. However, once again, you’ll find mixed results based on the variables of the study.

Skeptics argue that the evidence linking calcium supplements with CVD risk is inconclusive, even as others counter that normal-range doses are safe for healthy people.

Possible Side Effects

The Tolerable Upper Intake Level (UL) of calcium, which is defined as the highest amount a person should take, is:

  • 2,500 mg per day for adults ages 19 to 50
  • 3,000 mg per day for kids ages 9 to 18
  • 2,000 mg per day for older adults ages 51 and over

Excessive intake above the UL amount can result in constipation and bloating. Studies suggest that doses exceeding 4,000 mg have been associated with many health risks.

Some people who take calcium supplements even within these limits may still experience side effects. They include gas, bloating, constipation, or a combination of these symptoms. This may depend on the form of the calcium supplement.

One way to reduce symptoms is to spread calcium doses throughout the day. Another way is to take your calcium with meals.

With too much calcium, the supplement can cause high levels of calcium in the blood. This is called hypercalcemia. It can cause health issues that include kidney stones and other renal (kidney) damage. It also contributes to a condition called milk-alkali syndrome.

Drug Interactions

If you are taking medications, be sure to discuss calcium supplements with your healthcare provider before taking them. They can interact with drugs you may be taking. At the same time, particular drugs may interfere with how calcium is absorbed in the body.


Calcium supplements may offer benefits in reducing the risk of certain diseases, including colon cancer and high blood pressure. But there is no conclusive evidence of these benefits. Taking too much calcium has its own risks too. Among them is the potential to interfere with medications you already take.

Dosage and Preparation

The amount of calcium a person needs per day depends on their age. These are the U.S. Recommended Dietary Allowance (RDA) amounts, in mg, for calcium:

  • 1,000 for adult males (age 19 to 70) and females (age 19 to 50)
  • 1,200 for older people (women over age 50 and men over age 70)
  • 1,300 for children and adolescents (age 9 to 18)
  • 1,300 for pregnant and breastfeeding adolescents (age 17 to 19)
  • 1,000 for pregnant and breastfeeding adults (age 19 or older)

It’s best not to exceed 500mg in one single dose. For instance, if you are taking 1,000mg of calcium per day, you can split up the dosage (500mg in the morning and 500mg at night).

These levels can be achieved through calcium-rich diets as well as supplements. Keep in mind that these ranges are different than the maximum UL discussed above.

What to Look For

Not all calcium types contain the same amount of calcium that is actually absorbed by the body. You want to be sure the label of the calcium product you choose lists “elemental calcium” as well as the total calcium. If you do not see the words, you may want to purchase another type of supplement.

The two main forms of calcium supplements are calcium carbonate (calcite) and calcium citrate (Citracal).

Calcium carbonate is more commonly available. It must be taken with food because it needs stomach acids for the body to absorb it. It contains 40{7b6cc35713332e03d34197859d8d439e4802eb556451407ffda280a51e3c41ac} elemental calcium, the highest amount in supplement form for maximum absorption.

Most of the time, it is taken more than once daily. It is usually affordable and found in some over-the-counter antacid products, such as Tums. On average, each chewable tablet provides 200 to 400mg of elemental calcium.

Calcium citrate can be taken with or without food and is considered a better supplement for people with achlorhydria (low stomach acid levels). It also is better for people with inflammatory bowel disease or absorption disorders. Fortified fruit juices often contain a form of it.

Vitamin D and magnesium are important in calcium absorption. You may want to find a calcium supplement that includes one or both of them to ensure you optimize your dose.

Dietary Sources of Calcium

For the best calcium intake, aim to eat two to three servings of dairy a day. These include milk, yogurt, and cheese.

If you do not eat dairy, try foods fortified in calcium. They include yogurt alternatives, nut-based milks, orange juice, cereals, and tofu.

Salmon and other fatty fish contain calcium. Other good sources come from kale, cabbage, and other leafy green vegetables, but they are not immediately absorbed in the body.


The best sources of calcium are found in foods that provide your body with this essential mineral. If you plan on using supplements, consider the recommended dose for you. Follow your healthcare provider’s guidance if more calcium is needed. Be sure to find products from a reputable source that makes clear on the label just how much elemental calcium you’re getting.


The research on how calcium supplements may offer health benefits remains mixed. Calcium is known to support bone health and helps to prevent osteoporosis in women after menopause, for example.

But its benefits in supporting heart health or preventing colon cancer, among other conditions, remain unclear. Taking calcium supplements also may carry some risks, especially because of possible interactions with the drugs you take.

If you decide to take supplements, be sure to choose a high-quality product and take it within the recommended dose ranges. Check the label for the amount of “elemental calcium” so that you know how much calcium in any supplement is available for your body to truly use.

A Word From Verywell

Calcium supplements may offer health benefits, but your best source of calcium will always be from food sources. Talk with your healthcare provider before starting any calcium supplements.

Frequently Asked Questions

  • How can I get the maximum benefits of calcium supplements?

    Try to avoid taking calcium supplements when eating certain foods such as wheat bran, spinach, and rhubarb. The types of acids found in these foods (phytic acid, oxalic acid, and uronic acid) can interfere with calcium absorption.

  • Does sodium intake affect calcium absorption?

    High-sodium diets can raise the amount of calcium in your urine. Some healthcare providers suggest lower sodium intake for people after menopause. They also may recommend higher calcium intake when the sodium intake is more than 2,000 to 3,000mg per day.

  • Are bananas rich in calcium?

    No, bananas do not contain any calcium. They are a good source of potassium, magnesium, and vitamins B6 and C.

  • Are any fruits high in calcium?

    Yes, figs, papaya, and oranges are three fruits that contain calcium.

  • What medications interact with calcium supplements?

    Medications that may interact with calcium supplements include: 

    • Antacids that contain aluminum
    • Antibiotic
    • Anti-seizure medications
    • Beta-blockers
    • Bile acid sequestrants
    • Calcium-channel blockers
    • Corticosteroids
    • Digoxin
    • Diuretics
    • Estrogen
    • Fosamax (alendronate)

    Talk to your pharmacist about any potential drug-supplement interactions.