Evidence Based

9 Causes of Hypocalcemia (Calcium Deficiency)

Written by Jimmy Julajak, MS (Psychology) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
Medically reviewed by
Ognjen Milicevic, MD, PhD (Bioinformatics) | Written by Jimmy Julajak, MS (Psychology) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Calcium deficiency or hypocalcemia is much more common today than most people realize. It can trigger a wide range of symptoms, including muscle aches, irregular heartbeat, and fatigue. But what can cause it in the first place? Read on to understand what can make your calcium levels drop too low.

What is Hypocalcemia?


Hypocalcemia is when you have excessively low blood calcium levels (“hypo” = low, “calcemia” = calcium in the blood). This condition can be either transient and acute or chronic.

You may or may not experience symptoms, depending on the severity of your deficiency. Symptoms can range from barely-noticeable, mild changes to serious and life-threatening complications. Hypocalcemia can even lead to death if left untreated [1].

This is unsurprising given that calcium is the most abundant mineral in the human body. Every cell in your body needs it to function. Calcium supports your bones, heart, muscles, and nervous system. But only around 1% of your total body calcium is found in the blood. The remaining  99% is stored in your bones and teeth [2].


Symptoms of hypocalcemia are many and include [1]:

  • Muscle cramps
  • Tingling in the hands and feet
  • Fatigue
  • Confusion
  • Irregular heartbeat
  • Seizures
  • Osteoporosis
  • Dry skin
  • Tooth decay

This post will focus on the causes of deficiency that trigger these symptoms to start with. Read about calcium deficiency symptoms in more detail in this post.

Calcium Blood Test

A calcium test measures your calcium levels in the blood. Most commonly, the test estimates your total serum calcium levels and includes [3, 4]:

  • Calcium bound to proteins, mainly albumin (about 40%)
  • Calcium complexed with phosphate and citrate (about 10%)
  • Ionized calcium, also known as free or active calcium (about 50%)

You don’t need to prepare for this test or fast beforehand. A healthcare professional will simply collect a blood sample from your vein that will be analyzed.

The calcium blood test is often done as part of a routine metabolic panel. The basic metabolic panel (BMP) checks blood sugar, calcium, and electrolytes, as well as kidney function. The comprehensive metabolic panel (CMP) also includes cholesterol, protein levels, and markers of liver function [5].

Your doctor may also order an ionized (free) calcium test.

Ionized calcium is the body’s active form of calcium. It is assumed to be around 50% of the total blood calcium, although the exact percentage may vary. Ionized calcium levels are often just estimated based on total blood calcium and albumin levels. Testing ionized calcium is far more precise, but it requires special equipment and is expensive [3].

If you are suspected of being calcium deficient, your doctor may run more tests to confirm the diagnosis. Possible tests include measurement of magnesium, PTH, phosphate, and vitamin D [6, 1].

Low Calcium Levels

The normal range for calcium levels in adults is 8.5 to 10.5 mg/dL. These values can vary slightly from lab to lab. Hypocalcemia is defined as total blood calcium under 8.5 mg/dL. If calcium blood levels drop under 7 mg/dL, hypocalcemia is considered severe [7, 8, 6].

Serious calcium deficiency is rare. However, a lower-than-recommended dietary intake is common and can cause a mild, chronic deficiency with negative health consequences [9, 10].

Hypocalcemia Causes

1) Hypoparathyroidism

Calcium blood levels are mostly controlled by parathyroid hormone (PTH). Cells in your parathyroid gland – located in the neck just behind the thyroid – release PTH when they sense a drop in calcium blood levels [11].

PTH raises blood calcium levels by increasing the absorption of calcium from the gut and kidneys. This hormone also mobilizes calcium and phosphate from the bones: that is, it breaks down and frees the mineral content of bones to compensate for low calcium levels. This process is also known as bone resorption [11].

PTH also increases the amount of vitamin D that is converted to its active form, calcitriol. Active vitamin D increases calcium absorption in the gut [11].

If PTH levels drop too low, so does calcium.

Hypoparathyroidism is excessively low levels of parathyroid hormone. This condition can occur for several reasons [12, 13, 14]:

  • Cancer (e.g. breast cancer, lymphoma, multiple myeloma)
  • Damage to the parathyroid glands (e.g. from surgery)
  • Autoimmune disorders (e.g. polyglandular autoimmune syndrome)
  • Mitochondrial disorders (e.g. Kearns-Sayre syndrome)
  • Genetic disorders (e.g. DiGeorge syndrome)

It is also possible to have normal levels of PTH but experience the symptoms of low PTH. This condition is known as pseudohypoparathyroidism and happens when cells stop responding to PTH as they should [13].

2) Vitamin D Deficiency

If you do not get enough vitamin D (from sun or supplements), you can develop hypocalcemia. This is because vitamin D helps to absorb calcium from the gut. Vitamin D deficiency is the most common cause of hypocalcemia in primary care. It is estimated that up to 50% of the population may be deficient in vitamin D, so make sure you get enough [13, 15, 16].

3) Magnesium Deficiency

Magnesium deficiency is another factor that can lead to hypocalcemia. Without sufficient levels of magnesium, parathyroid hormone (PTH) cannot function properly. Magnesium is important for both the production and secretion of PTH [13, 17, 18].

4) Menopause

During menopause, the body’s production of PTH, estrogen and other hormones changes. Bone turnover (breakdown and replacement) rapidly increases and hypocalcemia is common. Women also have a higher risk of osteoporosis after menopause [19, 20].

5) Kidney Disease

Kidney disease causes hypocalcemia since damaged kidneys take up less calcium and let more of it slip out. Damaged kidneys also produce less vitamin D, which causes less calcium to be absorbed in the gut. Meanwhile, rising phosphate levels increase bound calcium and its flushing with the urine [13, 21].

6) Pancreatitis

Pancreatitis or pancreas inflammation is often accompanied by hypocalcemia, but the exact reason is unknown [17].

One theory is that lipopolysaccharides (LPS), toxins released from bacteria, end up in the bloodstream when the gut barrier is compromised. LPS causes calcium to accumulate in cells and tissues, leading to a drop in blood calcium levels [22].

7) Intestinal Diseases

Diseases that compromise calcium absorption in the gut can lead to hypocalcemia. This includes chronic diarrhea and inflammatory bowel diseases such as Chrons and ulcerative colitis. These diseases also decrease calcium, magnesium, and vitamin D absorption, putting patients at risk of deficiencies [23, 13].

8) Certain Drugs

Certain medications may cause (or contribute to) hypocalcemia. These include [24, 13]:

  • Bisphosphonates (osteoporosis treatment)
  • Cisplatin (chemotherapy)
  • Antibiotics (Rifampin, plicamycin, aminoglycosides)
  • Anti-seizure drugs
  • Calcitonin
  • Chloroquine (malaria)
  • Proton-pump inhibitors (acid reflux)
  • Corticosteroids

9) Not Consuming Enough Calcium

This one is perhaps obvious and self-explanatory. But a large study from 2007 showed that most Americans are not getting the calcium they need [25].

Take a look at the recommended daily intake (RDA) of calcium below, and make sure you get enough. If you don’t get enough from your diet, consider supplementing.

Be aware that certain substances in your diet can reduce absorption, or increase calcium loss. These include [26]:

  • Antinutrients (phytic acid, oxalic acid) that bind calcium in the gut
  • Alcohol, which reduces calcium absorption and limits vitamin D production
  • Caffeine, since it reduces absorption and increases calcium loss

Plant-Based Diets

If you follow a vegan diet, you might be at risk of certain nutrient deficiencies, including calcium and vitamin D. A carefully-planned vegan diet can be healthy and nutritious. Eat more vegetables high in calcium but low in oxalic acid, which inhibits calcium absorption. Good sources of calcium for vegans include [27, 28, 29]:

  • Tofu (calcium-set is best)
  • Kale, broccoli, sprouts, cauliflower, bok choy, collard greens

Some foods – such as fruit juices, soy or nut milk – are fortified with calcium.

If you can’t meet your dietary calcium needs, consider supplementing.

Dairy-free Diets

If you follow a paleo-style or carnivore diet, you are probably avoiding dairy, soy, and nuts. This leaves you with fewer options than vegans. Good calcium sources for people on meat-heavy diets include [27, 30]:

  • Canned or fresh fish with bones (sardines, sardelles, or even salmon)
  • Beef tripe

Those on a more liberal paleo diet have additional sources to choose from, including kale, broccoli, bok choy, and other leafy greens.

If you don’t supplement or eat fortified foods, the best solution for getting enough calcium on a strict paleo or carnivore diet is to consume bones.

Recommended Dietary Allowances (RDA) for Calcium

Below are shown the RDA for calcium. You should aim to get enough calcium every day, either from food or supplements. Going below the RDA for a short while is unlikely to cause harm, but it can lead to health problems in the long run [2].

0–6 months*200 mg200 mg
7–12 months*260 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 mg1,300 mg
19–50 years1,000 mg1,000 mg1,000 mg1,000 mg
51–70 years1,000 mg1,200 mg
71+ years1,200 mg1,200 mg

*Adequate Intake

Irregular Calcium Levels?

Chronic or severe hypocalcemia should always be treated by a doctor. There may be serious underlying medical conditions that you don’t want to miss.

If you have mild or temporary hypocalcemia, make it your goal to get more calcium and vitamin D. Our post about the benefits of calcium breaks down the pros and cons of supplementation. Also, be sure you know the difference between various calcium formulations and doses.

At SelfHacked, we also recommend LabTestAnalyzer, which helps you make sense of your lab results. It informs you which labs are not in the optimal range and gives you guidance about how to get them to optimal. It also allows you to track your labs over time. No need to do thousands of hours of research on what to make of your lab tests.

LabTestAnalyzer is a sister company of SelfHacked. The proceeds from your purchase of this product are reinvested into our research and development, in order to serve you better. Thanks for your support.


Low parathyroid gland function, menopause, and gut and kidney diseases can all cause hypocalcemia. Two common nutrient deficiencies – of vitamin D and magnesium – will also increase your risk of deficiency.

Rarely, you can become deficient if you’re not getting enough dietary calcium. Your risk is higher if you’re on a strict meat-based diet (avoiding both dairy and plant foods); a poorly-planned vegan diet can also lack calcium-dense foods.

Consult a doctor if your calcium levels are low to discover the underlying cause. If your hypocalcemia is mild, increase your intake of foods rich in calcium, magnesium, and vitamin D and/or consider supplementing.

About the Author

Jimmy Julajak

MS (Psychology)
Jimmy got his MSc from the University of Copenhagen.
Jimmy is a psychologist and researcher. He is particularly interested in the workings of the brain and strategies for improving brain health. He believes that people shouldn't hand over the responsibility for their health only to their doctors. His aim is to empower each person with easy-to-understand, science-based health knowledge.

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