Calcium is critical for bone health, optimal muscle activity, and other body processes such as blood clotting and heart function. How much calcium you need depends on your age and stage of life.

Photo of kale being chopped on cutting boardShare on Pinterest
Getty Images/Josh Manore

Calcium is the mineral you have the most of in your body. It makes up the structures of your bones and teeth and also helps maintain typical muscle function, blood clotting, nerve transmission, and other body processes.

About 99% of your body’s calcium is stored in your bones. Your bones act as a calcium reservoir that your body draws from to maintain balance.

Calcium occurs naturally in many foods, especially dairy products. Calcium-fortified foods are also readily available, and calcium supplements can help boost your calcium intake if needed.

Your body also needs vitamin D to absorb and maintain calcium levels. You need a balance of both nutrients for your body to work properly.

Calcium has many roles in your body and is particularly important during certain developmental stages. Calcium is important in the body for:

  • Bone health: Calcium is critical for the development, health, and continued maintenance of bone. Women beyond menopause need calcium to maintain bone density and prevent osteoporosis.
  • Blood clotting: Calcium plays a role in your blood’s ability to clot. While many chemicals and nutrients are involved, calcium is an important factor.
  • Cardiac function: Calcium helps maintain the action of your heart muscle by relaxing the smooth muscles around your blood vessels. Calcium has also been linked to lower blood pressure.
  • Muscle contraction: Calcium can help balance muscle contraction. Calcium is released when a muscle is stimulated. This helps the muscle contract. When the calcium is pumped out of the muscle, it can relax.
  • Preventing preeclampsia: Consuming certain amounts of calcium during pregnancy can aid in lowering blood pressure, reducing the risk of preeclampsia.
  • Improved cholesterol levels: Calcium is also known to help improve certain cholesterol levels in the blood.

Your daily calcium requirements change depending on your age and stage of life. According to a 2022 fact sheet published by the Office of Dietary Supplements, these are the general daily requirements determined by the Food and Nutrition Board:

Recommended dietary allowance (RDA) of calcium in milligrams (mg):

AgeMaleFemalePregnant person
0–6 months200 mg200 mg
7–12 months260 mg260 mg
1–3 years700 mg700 mg
4–8 years1,000 mg1,000 mg
9–13 years1,300 mg1,300 mg
14–18 years1,300 mg1,300 mg1,300 mg
19–50 years1,000 mg1,000 mg1,000 mg
51–70 years1,000 mg1,200 mg
70+ years1,200 mg1,200 mg

Notice that calcium needs are the same for males and females, until the age of 50 years. At this time, a female’s calcium needs increase slightly.

During pregnancy, calcium is important to reduce the risk of preeclampsia. For pregnant people with low calcium intakes, a doctor may suggest calcium supplements.

Calcium deficiencies occur when the amount of calcium in your blood (your serum calcium level) dips below 8.5 milligrams per deciliter (mg/dL). With mild or chronic calcium deficiencies, you may not have any symptoms. But if the condition gets more severe, symptoms will develop.

Symptoms of a calcium deficiency can include:

  • muscle spasms
  • depression
  • confusion
  • muscle cramps
  • hallucinations
  • weak and brittle nails
  • easy bone fractures
  • seizures

Certain health conditions or life changes can contribute to a calcium deficiency. These can include:

  • menopause
  • hypoparathyroidism
  • malnutrition or malabsorption
  • pancreatitis
  • septic shock
  • certain medications, including steroids and some chemotherapy drugs
  • kidney failure
  • lack of a parathyroid gland (due to surgery)
  • frequent blood transfusions

Calcium is naturally found in several foods. While dairy products are the best known source of calcium, other nondairy foods can also contain high calcium levels.

Some calcium-rich foods include:

Vegetables that contain calcium but have high oxalic acid levels, such as spinach, may reduce your body’s ability to absorb calcium.

While it’s most effective to meet your calcium needs from dietary sources, calcium supplements can help boost your calcium levels if you aren’t getting enough.

The amount of calcium in supplements varies, but most supplements contain between 300 and 500 mg of calcium. It’s common to find vitamin D included in calcium supplements in order to enhance calcium absorption.

The two most common forms of calcium in supplements are calcium carbonate and calcium citrate. Each of these forms contains different amounts of elemental calcium, which is the actual amount of calcium in the supplement. Calcium carbonate is 40% calcium by weight, whereas calcium citrate is 21% calcium by weight.

Regardless of the supplement type, calcium absorption is highest when you take supplements with food, and doses are in the amount of 500 mg or less.

Supplements may occasionally cause minor side effects such as gas, constipation, bloating, or a combination of these symptoms. Lowering your dose or switching to a different supplement may help reduce these side effects. A doctor can help you determine the best type of supplement and dosage for you.

Excessive calcium levels (hypercalcemia) are rare in the general population, but it may result from conditions such as cancer or primary hyperparathyroidism.

People with severely elevated calcium levels may experience:

  • poor muscle tone
  • constipation
  • kidney issues
  • low phosphate levels (hypophosphatemia)
  • excessive urination
  • nausea
  • fatigue
  • higher risk of death from cardiovascular disease
  • unexplained weight loss
  • irregular heart rhythms (arrhythmia)

Calcium does have the potential to interact with certain medications. This can either cause the medication to not function properly, or the medication could affect the amount of calcium in your body.

Medications known to interact with calcium include:

  • Levothyroxine: This drug is prescribed to treat hypothyroidism or thyroid cancer. Calcium carbonate supplements can prevent its absorption, so you should not take them within 4 hours of taking levothyroxine.
  • Lithium: Commonly used to treat bipolar disorder, long term lithium use can result in hypercalcemia. Taking calcium supplements in addition to lithium can increase this risk.
  • Dolutegrevir: Used in HIV treatment, taking calcium supplements along with dolutegrevir can reduce the effectiveness of the medication. Careful timing of calcium supplements is recommended for people taking dolutegrevir.
  • Quinolone antibiotics: Calcium supplements are known to reduce the effectiveness of this class of antibiotic medication. Any calcium supplements should be taken at least 2 hours before or after this medication.

If you regularly take calcium supplements, let your doctor know before starting any new medication so you can prevent possible interactions.

Calcium is the mineral you have the most of in your body. It is critical for the development of strong, healthy bones and for several body functions. Your body requires vitamin D to absorb and use calcium.

Many food options can help you meet your daily calcium needs, but doctors sometimes recommend calcium supplements for certain health conditions or if you aren’t able to get enough dietary calcium.

Calcium deficiencies caused by diet alone are rare, but some health conditions or life changes may reduce your calcium levels. Staying on top of your body’s calcium requirements can help maintain bone strength and structure, maintain cardiovascular function, and lower cholesterol levels.