Hypocalcemia: Symptoms, Causes, and Health Impacts

Calcium plays a critical role in keeping our bones, muscles, and overall health strong. When calcium levels drop too low, it can lead to a range of health issues that often go unnoticed until they become serious. In this article, we’ll explore what calcium deficiency looks like, why it matters, and how you can prevent or manage it effectively.

What Is Calcium Deficiency?  

Calcium deficiency refers to low levels of calcium in the body. Almost all the calcium in the body is stored in the bones and teeth. Calcium deficiency can therefore lead to osteoporosis, a condition in which bones become weak and prone to fractures. In children, calcium deficiency can cause a condition called rickets (softening and weakening of bones). For these and other bone disorders, the levels of calcium and vitamin D are interrelated. 

Note: The term hypocalcemia refers to low levels of calcium in the blood (and not in the bones).

The Importance of Calcium  

Calcium is the most abundant mineral in the body. A person weighing 150 lbs has about 1.2 kilograms of calcium in their body, 99% of which is stored in the bones in the form of calcium hydroxyapatite.

We need calcium to build strong bones and teeth and to perform other important processes like muscle contraction, nerve signal transmission, blood flow in blood vessels, and hormone release. Vitamin D plays an important role in helping the body absorb calcium from the diet.

Hypocalcemia Symptoms

Early Symptoms

As mentioned, hypocalcemia refers to low calcium levels in the blood. Early symptoms of mild hypocalcemia can include:

• Muscle cramps, especially in the back and legs

• Brittle nails

• Coarse, dry hair

• Dry, scaly skin

If left untreated, hypocalcemia can lead to an increased risk of mental symptoms such as:

• Confusion

• Memory problems

• Irritability

• Restlessness

• Depressive symptoms

• Fatigue

• Hallucinations (seeing or hearing things that aren’t there)

Serious Symptoms

Severe hypocalcemia (very low calcium levels) can have serious effects on many organs in the body, including the muscles, nerves, and heart. Symptoms of severe hypocalcemia may include:

• Numbness and tingling in the fingers, toes, lips, and tongue.

• Muscle aches and pains.

• Laryngospasm (muscle spasms in the throat, which can make it difficult to breathe).

• Tetany (spasm and stiffening of muscles).

• Congestive heart failure.

• Abnormal heart rhythms (arrhythmias).

• Seizures.

Causes and Risk Factors  

Common Causes

The three most common causes of hypocalcemia include:

• Hypoparathyroidism (underactive parathyroid glands and low parathyroid hormone or PTH secretion). This can occur due to an inherited disorder or surgical removal of the parathyroid glands. Parathyroid hormone (PTH) is secreted by the parathyroid glands in the neck. This hormone moves calcium from the bones to the blood when serum calcium (blood calcium) levels are low.

• Vitamin D deficiency due to inadequate dietary intake, lack of exposure to sunlight, or inherited disorders. The body needs vitamin D to absorb calcium.

• Renal failure. People with chronic renal failure can develop hypocalcemia due to high serum phosphate levels and decreased formation of vitamin D in the kidneys.

Other potential causes of hypocalcemia (low blood calcium) include:

• Taking certain medications can cause hypocalcemia, such as:

  • Corticosteroids 

  • Bisphosphonates for osteoporosis 

  • Denosumab for osteoporosis 

  • Rifampin for tuberculosis 

  • Cinacalcet for chronic kidney disease 

  • Calcitonin to treat Paget’s disease of bone 

  • Chloroquine for malaria 

  • Foscarnet for viral infections

  • Plicamycin for cancer

• Pseudohypoparathyroidism is an inherited disorder in which the body does not respond properly to parathyroid hormone (PTH).

• Hypomagnesemia (low blood magnesium levels). The parathyroid glands need magnesium to make parathyroid hormone (PTH).

• Acute pancreatitis (inflammation of the pancreas).

• Certain rare genetic conditions, such as DiGeorge syndrome.

• Pregnancy. There are reports of hypocalcemia during pregnancy, mainly related to poor diet, hyperemesis gravidarum, or underlying diseases.

Risk Factors  

Risk factors for hypocalcemia include:

• Vitamin D deficiency.

• Parathyroid disorders.

• Parathyroid gland surgery or thyroidectomy (thyroid removal) – this can lead to profound hypocalcemia called hungry bone syndrome, where calcium is rapidly consumed by bones, leading to low blood concentrations of calcium.

• Family history of genetic disorders, such as genetic vitamin D metabolism disorders or DiGeorge syndrome.

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Daily Calcium Requirements  

How Much Calcium Should You Consume Per Day?  

The recommended daily intake of calcium per day in different age groups is as follows:

Note: The body maintains calcium homeostasis (tightly regulates the movement of calcium between bones and blood). Eating more calcium in food will not raise your total serum calcium concentration (blood calcium level). However, adequate calcium intake is necessary to maintain healthy bones.

Importance of Vitamin D For Calcium Absorption  

The body needs vitamin D to absorb calcium from food. Without enough vitamin D, only about 10-15% of dietary calcium is absorbed. When there is enough vitamin D, about 30 to 40% of calcium from food is absorbed.

Which Disease Is Caused By a Deficiency of Calcium?

Chronic calcium deficiency can result in bone disorders such as rickets in children and osteopenia, osteomalacia, or osteoporosis in adults. It can also cause disruption in muscle, nerve, and heart function and other bodily processes.

Diagnosing and Treating Calcium Deficiency  

How Is Calcium Deficiency Diagnosed?  

Doctors can check serum calcium concentrations (blood levels of calcium) with a blood test. Calcium levels are included in routine blood tests such as a comprehensive metabolic profile.

Total serum calcium concentrations in healthy people range between 8.8 and 10.4 mg/dL (2.2 and 2.6 mmol/L). Any level below 8.5 mg/dL is considered hypocalcemia. 

Doctors can also measure ionized calcium, which is the biologically active form of calcium. The serum ionized calcium concentration in healthy people ranges between 4.6 to 5.3 mg/dL (1.15 and 1.33 mmol/L). In certain cases, such as people with low serum albumin concentration, total calcium may be low but ionized calcium is normal.

As mentioned, the skeleton stores 98% of the body’s calcium. Total calcium stores in the bone can be measured with a test called dual X-ray absorptiometry (DEXA scan), which checks bone mineral density.

Treatment Options

Your doctor can prescribe oral calcium supplements to raise your serum calcium level to the normal range. 

Along with replacing calcium, it’s also important to treat the underlying cause of low calcium (hypocalcemia). For example, if you have low vitamin D levels, your doctor may prescribe vitamin D analogs in supplement form. 

Other treatments may include synthetic forms of parathyroid hormone (PTH) to raise PTH levels, recombinant human parathyroid hormone, and intravenous calcium gluconate for severe hypocalcemia or acute hypocalcemia.

In some people, hypocalcemia (low blood calcium level) requires lifelong treatment. In others, calcium supplements can correct a calcium deficiency in a few weeks.

When To Go To The ER For Hypocalcemia

Go to the ER if you have severe symptoms such as difficulty breathing, muscle spasms, sudden swelling or weight gain, fast or racing heartbeat, or convulsions. 

Keep all your healthcare appointments if you have chronic hypocalcemia so that your doctor can monitor your calcium levels and see if the treatment is working. 

Preventing Calcium Deficiency  

Dietary Sources and Calcium-Rich Foods

Dairy products are some of the highest in calcium. In the United States, people get about three-fourths of their dietary calcium intake from dairy products like milk, yogurt, and cheese, which are naturally rich sources of calcium. 

In addition to dairy products, other calcium-rich foods include canned fish (sardines, salmon) and vegetables like broccoli, kale, and bok choy (Chinese cabbage). 

Calcium-fortified foods and drinks such as fruit juices, milk, breakfast cereals, and tofu can also help you meet your daily calcium needs.

Note: Certain plant compounds, such as oxalic acid and phytic acid, can form indigestible salts with calcium and decrease calcium absorption. For this reason, only 5% of the calcium in spinach is absorbed compared to 27% of the calcium in milk.

How Can I Get 1000 mg of Calcium Daily?

You can get 1,000 mg of calcium daily by eating calcium-rich foods, such as:

Calcium Supplements

Calcium supplements are available in various forms and can increase calcium in the body quickly. You can take calcium in the form of calcium-only supplements, calcium and vitamin D supplements, and multivitamins. The amount of calcium in dietary supplements can vary widely, but is typically 200 mg to 500 mg. 

The two most common salts of calcium in dietary supplements are calcium carbonate and calcium citrate. 

Calcium carbonate is less soluble in people with low stomach acid levels. 

Calcium citrate is less dependent on stomach acid levels for absorption. Notably, calcium carbonate contains 40% calcium by weight, whereas calcium citrate contains 21% calcium by weight. 

The amount of elemental calcium in a supplement will be listed on the label.

Generally speaking, calcium supplements are absorbed better when taken with food. 

Other forms of calcium supplements include calcium sulfate, calcium ascorbate, calcium gluconate, calcium phosphate, calcium chloride, calcium lactate, and microcrystalline hydroxyapatite.