Calcium is the most abundant mineral in your body—and for good reason. (25) Not only is it essential for building and maintaining strong bones and teeth, calcium also supports your cardiovascular system, proper nerve and muscle function, and colon health. (9)(14) And yet, as critical as this mineral is, 42% of Americans and 68% of Canadians aren’t getting the recommended amount of dietary calcium. (25)(44) Over time, that can lead to some potentially serious health consequences.

Calcium deficiency causes

Over time, a diet low in calcium (e.g., a dairy-free or vegan diet) can result in a deficiency of this nutrient. (45) While including more calcium in your diet is a good start, boosting your levels may not be as straightforward as simply adding dairy or other calcium-rich foods to your grocery cart. Here’s why: calcium can only provide benefits if it is absorbed by the body—and that requires an adequate amount of vitamin D. Vitamin D (as 1,25 dihydroxyvitamin D) binds to receptors in the intestine, which stimulates the transport of calcium from your intestine into your bloodstream. (31) Once calcium is in the blood, its levels are tightly controlled by something called parathyroid hormone (PTH). (35) Low vitamin D levels or a dysfunction in your PTH activity can cause a deficiency, even if your calcium intake is adequate.

Other common causes of calcium deficiency include pharmaceutical interactions, gastrointestinal or kidney issues, menopause, and pancreatitis.

Pharmaceutical medication interactions

Some medications contribute to a calcium deficiency, including anti-seizure medications, bisphosphonates, glucocorticoids, and proton pump inhibitors. (24)(30)(42) For instance, anti-seizure drugs like phenobarbital, glucocorticoids, and proton pump inhibitors reduce calcium absorption. (19)(23)(32) Bisphosphonates, on the other hand, have been shown to reduce serum calcium levels. (37)

Gastrointestinal problems

Certain chronic gut issues may impair nutrient absorption and contribute to a calcium deficiency. Studies have shown that this is especially true for those suffering from gastroenteritis or a chronic inflammatory bowel disease like Crohn’s disease or ulcerative colitis. (6)(15) Findings out of Emory University in Atlanta, Georgia suggest that the degree and location of the gut inflammation in patients with IBD can impact calcium absorption, as can the use of glucocorticoids, which are used to reduce intestinal inflammation. (29)

Kidney disorders

Kidney disease can cause a calcium deficiency. Healthy kidneys play a key role in regulating how much calcium is retained and how much is shuttled out of the body. (27) Damaged kidneys retain less calcium and produce less vitamin D. This results in less calcium being absorbed in the gut. As a result, higher amounts of calcium are excreted from the body through the urine. (4)(18)


Practitioner showing patients an x-ray
Falling calcium levels during and after menopause can silently increase the risk of osteoporosis and other health problems in postmenopausal women.



The hormone estrogen plays a role in calcium absorption by increasing vitamin D levels in the blood. During menopause, a woman’s calcium levels begin to drop due to a decline in estrogen levels. (5) In addition, clinical research shows that by the time a woman has gone through menopause, serum PTH levels are significantly higher and calcium levels are markedly lower. As a result, this increases bone turnover and leads to greater postmenopausal bone loss. (38)

Did you know? A severe calcium deficiency after menopause can increase the accumulation of visceral fat—a dangerous type of internal fat that surrounds key organs, including your liver, stomach, and intestine. (36) Visceral fat increases the risk of cardiometabolic problems such as heart disease, type 2 diabetes, and obesity. (16)


Inflammation of the pancreas, also known as pancreatitis, is often accompanied by a calcium deficiency. While scientists haven’t pinpointed the reason for this, some researchers believe that an imbalance in other minerals like magnesium or an increase in PTH may be involved. (2)

Complications and signs of calcium deficiency

Mild to moderate calcium deficiency typically doesn’t present with any signs of a deficiency. (13) However, this form of calcium deficiency can, over a long period of time, lead to “silent” conditions” such as osteoporosis or high blood pressure. (14)

Excessively low levels—technically known as hypocalcemia—can, however, trigger a variety of symptoms, including:

  • Abnormal heart rhythm (12)
  • Brain fog and memory loss (39)
  • Depression (34)
  • Dry skin (7)(39)
  • Fatigue (3)(28)(39)
  • Muscle cramps and spasms (8)(39)
  • Numbness and tingling in extremities (8)(9)
  • Osteopenia and osteoporosis (40)
  • Premenstrual syndrome (1)
  • Seizures (22)(39)
  • Tooth decay and gum disease (39)(47)
  • Weak, brittle nails (39)

Diagnosing low calcium levels

Given that a mild to moderate calcium deficiency often doesn’t present with any symptoms, the best way to tell if your levels are suboptimal is with a simple blood test. There are two types of calcium tests. The first measures total calcium that is bound to proteins like albumin. Albumin binds to calcium and transports it through your blood. The second test, known as an ionized calcium test, measures the amount of calcium that is not bound to these proteins. This “free” calcium is the amount of active calcium in the blood. (10)(26)

Healthy total calcium levels range from 8.5 to 10.5 mg/dL. (20) Anything less than 8.5 mg/dL is classified as hypocalcemia. (41) If your blood levels drop below 7 mg/dL, the deficiency is considered severe. (21)


Woman picking vegetables at a farmers market
Not all calcium comes from dairy. Leafy greens, soy, and even some fish can help you meet your daily quota.


How to treat calcium deficiency

A mild to moderate deficiency can often be corrected with dietary changes and supplementation. The recommended dietary allowance (RDA) for adults up to the age of 50 is 1,000 mg of calcium daily. Women over 50 and everyone over the age of 71 should increase their intake to 1,200 mg per day. (9)

The table below summarizes good sources of dietary calcium based on information from the U.S. Department of Agriculture. (9)


Table showing good sources of calcium
Calcium is found in many plant and animal-based foods.


Supplements can also help increase your calcium levels. The two most popular and widely available forms are calcium carbonate and calcium citrate. Calcium carbonate requires stomach acid to be absorbed by the body, so it should be taken with food. Calcium citrate, on the other hand, can be taken with or without food. (9) What’s more, research out of the UT Southwestern Medical Center found that calcium citrate is more readily absorbed and is more bioavailable. (43)

Whichever you choose, the amount of calcium that’s absorbed from supplements depends on how much elemental calcium it contains. The more elemental calcium, the less efficiently it’s absorbed. In general, calcium carbonate contains approximately 40% elemental calcium, while calcium citrate is made up of 21% elemental calcium. (9)

Did you know? Some over-the-counter chewable antacids contain 200 to 400 mg of elemental calcium in each dose. (9)

Another consideration is the amount of calcium your body can absorb. Studies show that the body can only absorb 500 mg of calcium at a time. (46) If you’re depending on supplements to meet your daily intake, your practitioner may recommend dividing the doses. For example, if you’re taking 1,000 mg of supplemental calcium, it may be recommended to take 500 mg at two separate times during the day to optimize absorption. (9)


Woman smiling in the sun
Just 10 to 15 minutes of sun exposure daily can help increase your vitamin D levels and, as a result, improve your body’s ability to absorb calcium from food and supplements.


As vitamin D is necessary for calcium absorption, treatment may also include supplementing with vitamin D2, the active form of the “sunshine nutrient.” (17) For dosing recommendations suitable for your individual needs, be sure to talk to your healthcare provider before starting supplementation since excess calcium intake can be just as harmful as not getting enough. (11)

While increasing your intake of calcium through your diet or supplementation may help prevent or address deficiency, if you’ve been diagnosed with severe hypocalcemia, intravenous calcium may be required. In some cases, treatment can be combined with oral calcium and vitamin D supplementation, if needed. (17)

The bottom line

Calcium is essential for a wide variety of functions throughout the body. While a mild deficiency may be corrected by adding more calcium-rich foods to your daily diet or by taking supplemental calcium and vitamin D, more severe deficiencies may require intravenous calcium treatments. If your health care practitioner suspects a deficiency, they may order a blood test to check your levels.

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