Calcium, an abundant mineral in your body, has a big job: To strengthen your skeleton. About 98% of the calcium in your body is stored in your bones. You also need calcium for your teeth, heart, nerves, and muscles to function properly.¹

A deficiency in calcium can lead to bone-weakening osteoporosis and possible fractures in your hip, spine, and wrist. A diet low in calcium is one of several factors that can increase your risk of bone loss.¹

Here's how to tell if you're getting enough calcium to keep your bones strong.

Your body can't make its own calcium. It has to come from your diet and/or a supplement. The recommended dietary allowance (RDA) for calcium is:²

Your bones absorb calcium from your bloodstream. With plenty of calcium on board, you'll have enough circulating in your bloodstream to help protect you from a calcium deficiency. Healthy people typically have blood levels of calcium between 8.8 and 10.4 milligrams/deciliter.²

"In general, a deficiency is very low dietary intake of a vitamin or mineral that can result in a deficiency disease," said Allison Herries, RDN, a registered dietitian and Health review board member.

A calcium deficiency can result in osteoporosis or other calcium-related disorders.² Hypocalcemia, a type of calcium deficiency, is defined as having a blood level of calcium less than 8.5 milligrams/deciliter.²

A substantial proportion of people in the U.S. have calcium inadequacy. That means they consume less than the recommended amounts of calcium.

"Sometimes the terms inadequacy and deficiency get used interchangeably, which can be confusing. However, they are not the same thing," said Herries.

"Basically, inadequacies occur when nutrient intake is above the level associated with deficiency but below dietary recommendations," explained Herries. "Inadequacies are much more common than actual deficiencies and may or may not progress to the point of being considered a deficiency."

In the U.S., men get roughly 1,083 milligrams per day of calcium from food and beverages; women's intake of calcium from their diet is 842 milligrams per day. If you include dietary supplements, those levels rise to about 1,156 milligrams for men and 1,009 milligrams for women.²

When you have low levels of calcium in your bloodstream, especially for prolonged periods, that means there's less available for your bones, Herries noted. The body tries to maintain a steady balance by "not placing calcium 'into storage.'"

The body sometimes takes, or reabsorbs, calcium from bones or teeth to maintain adequate blood calcium levels, added Herries. "This may then increase your risk of developing osteoporosis in the future," she said.

Hypocalcemia, a severe form of deficiency in calcium, can result from not getting enough vitamin D or magnesium. Other causes of hypocalcemia can include not producing enough parathyroid hormone, critical illness, and certain medications, such as drugs that prevent or slow bone loss (called bisphosphonates), chemotherapy drugs, and proton pump inhibitors for acid reflux.²

Certain people may be more vulnerable to developing a calcium deficiency. You may be at increased risk if:

Women lose roughly 1% of bone mineral density per year after menopause, when menstrual periods cease. To keep bones strong after menopause when the risk of osteoporosis increases due to lower estrogen levels, 1,200 milligrams of daily calcium are recommended.²

Dairy products are loaded with calcium and fortified with vitamin D. People who avoid eating dairy products, such as milk, cheese, and yogurt due to lactose intolerance, a milk allergy, being a vegan, and other reasons, are more likely to fall short on meeting their calcium requirements.²

In people with this rare disorder, the body produces too little parathyroid hormone, which results in low levels of circulating calcium.³

Magnesium causes the parathyroid glands—two small glands in the neck—to release a hormone that increases blood calcium levels when they're low. A magnesium shortfall can lead to hypocalcemia, or low blood calcium.⁴

Men and women need 310 to 420 milligrams per day of magnesium, depending on age. Diet surveys show that Americans consistently get less than the recommended amounts.⁴

Vitamin D has long been thought to help your body absorb calcium. It is available through through food, supplements, and sunlight, which causes your skin to produce vitamin D. The RDA for vitamin D is 600 international units (IU) for men and women 70 and younger and 800 IU for adults over 70.⁵

However, new evidence suggests that taking vitamin D supplements may not be the key to preventing fractures, at least in many midlife and older adults. Compared with taking a placebo, supplementing with vitamin D failed to result in a significantly lower fracture risk.⁶

"Overall, the results from this large clinical study cast doubt upon the use of daily vitamin D supplements to reduce fractures in healthy U.S. adults," said Herries. "These findings are important since many healthcare professionals continue recommending vitamin D supplements for overall health."

However, researchers did not design the study to test vitamin D supplements in people with vitamin D deficiency. So the findings might not apply to adults with vitamin D deficiency or osteoporosis, Herries pointed out.

A deficiency in calcium may not have symptoms. Osteoporosis, for example, can be sneaky. You may not know you have it until you break a bone.⁷ Similarly, the most severe form of a deficiency in calcium, hypocalcemia, may be symptomless.²

But when it does cause symptoms, you might have:²

See your doctor if you experience these symptoms. Signs of severely low blood calcium may include cases, hypocalcemia can cause kidney damage, depression, bipolar disorder, brain calcification, cataracts, congestive heart failure, seizures, burning and prickling sensation in the hands and feet, or coma.²

A deficiency in calcium can be diagnosed with a test that measures the amount of calcium in your blood. There are two types:⁸

These blood tests usually take just minutes. To check for hypoparathyroidism, your doctor may also order another blood test that measures phosphorus, magnesium, and parathyroid hormone and a urine test.⁹

Treatment options vary depending on the severity of the calcium deficiency and what's causing it. Healthcare providers may advise people with mild symptoms to take calcium/vitamin D supplements. For severe hypocalcemia, intravenous infusions may be necessary.¹¹

If hypoparathyroidism is causing low blood calcium, calcium/vitamin D supplements may be needed for life. Your doctor may also prescribe parathyroid hormone, a once-a-day injection, and other medications to improve the body's calcium levels.³

Reduce your risk of bone loss by eating plenty of calcium-rich foods, including milk, cheese, and yogurt. Low-fat and nonfat dairy products are loaded with calcium and fortified with vitamin D, offering roughly 300 milligrams of calcium per one-cup serving.²

Other calcium sources include tofu, fortified cereal, calcium, and vitamin D-fortified orange juice, soy and almond milk, and other calcium-fortified beverages. Note: If you buy a fortified beverage, shake the container before pouring yourself a glass. Added calcium can settle at the bottom.⁹

Read labels and choose foods with 20% to 30% daily value (DV), which means a food contains 200 to 300 milligrams of calcium per serving.¹² Aim for at least three servings of calcium-rich food per day.¹⁰

Consider taking a calcium/vitamin D supplement if you can't get enough from food alone. For best calcium absorption, take it with a meal or snack.² Think of eating well as making deposits in your bone bank account. At any age, a calcium-rich diet is important for reducing the risk of a deficiency in calcium and optimizing bone health.

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