What does calcium do in the body?

Calcium has several important functions.

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Path to improved health
Things to consider
Questions to ask your doctor

These include:

helping build bones and keep teeth healthy
regulating muscle contractions, including your heartbeat
making sure blood clots normally

A lack of calcium could lead to a condition called rickets in children, and osteomalacia or osteoporosis in later life.

Sources of calcium include:

milk, cheese and other dairy foods
green leafy vegetables – such as curly kale, okra but not spinach (spinach does contain high levels of calcium but the body cannot digest it all)
soya drinks with added calcium
bread and anything made with fortified flour
fish where you eat the bones – such as sardines and pilchards

Adults aged 19 to 64 need 700mg of calcium a day.

You should be able to get all the calcium you need from your daily diet.

Taking high doses of calcium (more than 1,500mg a day) could lead to stomach pain and diarrhoea.

You should be able to get all the calcium you need by eating a varied and balanced diet.

If you take calcium supplements, do not take too much as this could be harmful.

Taking 1,500mg or less a day is unlikely to cause any harm.

Page last reviewed: 03 August 2020
Next review due: 03 August 2023

About 99% of the body’s calcium is stored in the bones, but cells (particularly muscle cells) and blood also contain calcium. Calcium is essential for the following:

Formation of bone and teeth
Normal functioning of many enzymes

The level of calcium in blood is regulated primarily by two hormones:

Stimulates bones to release calcium into blood
Causes the kidneys to excrete less calcium in urine
Stimulates the digestive tract to absorb more calcium
Causes the kidneys to activate vitamin D, which enables the digestive tract to absorb more calcium

Calcitonin is produced by cells of the thyroid gland. It lowers the calcium level in blood by slowing the breakdown of bone, but only slightly.

Calcium is a mineral in your body that is also found in many foods. Most of the calcium in your body is in your bones and teeth. There is also calcium in your blood, muscles, other body tissues, and the fluid between your cells.

Path to improved health

You need calcium to keep your bones and teeth healthy and strong throughout your life. Your body also uses calcium to:

Help blood vessels and muscles work properly.
Help release hormones and enzymes that keep your body working properly.
Help your nerves carry messages throughout your body.
Help control important nutrients, such as magnesium, phosphorus, and potassium.

Your body can’t make more calcium. So it’s important for you to provide it with the calcium it needs. The amount of calcium you need each day depends on your age, your sex, and other factors. For example, vitamin D improves calcium absorption. Alcohol reduces calcium absorption. Doctors recommend:

Children ages 0-6 months: 200 milligrams (mg) per day.
Children ages 6-12 months: 260 mg per day.
Children ages 1-3: 700 mg per day
Children ages 4-8: 1,000 mg per day
Children ages 9-18: 1,300 mg per day
Adults ages 19-50: 1,000 mg per day
Adult men ages 51-70: 1,000 mg per day
Adult women ages 51-70: 1,200 mg per day
Adults ages 71 and older: 1,200 mg per day.

It’s best to spread your calcium throughout the day. Eat calcium-rich foods at every meal rather than all at once. Be sure to get enough vitamin D each day to help your body absorb the calcium.

Nonfat and low-fat dairy products (yogurt, cheese, and milk) are good sources of calcium. Vegetable sources of calcium include dried beans, kale, spinach, and collard greens. Animal sources of calcium include fish with soft bones, such as sardines and salmon. For example, 2 ounces of nonfat American cheese has 447 mg of calcium. One cup of skim milk has 299 mg of calcium. And 3 ounces of pink salmon has 183 mg of calcium. Some foods may be fortified with calcium (orange juice, bread, pasta, dry breakfast cereal, and dairy substitutes).

If you’re not getting enough calcium from dietary sources, talk to your doctor about a calcium supplement. Depending on your age, sex, overall health, and other factors, your doctor might recommend that you take a calcium supplement. Also, your doctor can tell you if a calcium supplement will affect any medical conditions you have. He or she will need to know about any prescription or over-the-counter (OTC) medicines, or other dietary supplements you are taking. Calcium supplements can affect the way certain medicines work. For example, calcium supplements can interfere with blood pressure and synthetic thyroid medicines, bisphosphonates, and antibiotics. Other supplements, such as iron, can affect how the body absorbs, uses, or gets rid of medicines or supplements.

There are 2 main types of calcium supplements: calcium carbonate and calcium citrate. Both types are available without a prescription. Over-the-counter calcium supplements are available in tablet, chewable, liquid, and powder form. Other types of calcium include calcium gluconate and calcium lactate. These contain less elemental calcium than calcium carbonate and calcium citrate.

If a supplement is right for you, your doctor will help you decide which one to take. He or she will also explain what amount of calcium to take each day and how to take the supplement. For example, calcium carbonate should be taken with meals to avoid possible unpleasant health effects (also called adverse effects). Taking it with meals helps your body to better absorb it. Calcium citrate can be taken on an empty stomach.

Things to consider

If your body doesn’t get enough calcium and vitamin D to support important functions, it takes calcium from your bones. This is called losing bone mass. Losing bone mass makes the inside of your bones become weak and porous. This puts you at risk for the bone disease osteoporosis.

Certain populations are at higher risk for low calcium levels, including:

Postmenopausal women.
People who have lactose intolerance and avoid dairy products.
Women who have an eating disorder (for example, anorexia).
People who do not eat animal, fish, or dairy products (vegans).
People who take certain medicines for osteoporosis.
People who have parathyroid disorders, inflammatory bowel disease, or liver or kidney disease.

Unfortunately, getting more calcium than your body needs can cause adverse (negative) effects. This includes kidney stones, frequent urination, belly pain, nausea/vomiting, and fatigue. It is rare to get too much calcium from food alone. There is an amount of calcium that most people can take each day without developing problems. This is called the tolerable upper intake level. Doctors recommend the following tolerable upper intake levels by age:

Ages 0-6 months: 1,000 mg per day
Ages 7-12 months: 1,500 mg per day
Ages 1-8: 2,500 mg per day
Ages 9-18: 3,000 mg per day
Ages 19-50: 2,500 mg per day
Ages 51 and older: 2,000 mg per day

Talk to your doctor about whether supplements are right for you.