An Overview of Hypocalcemia

Dealing With an Abnormal Lab Test

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Hypocalcemia refers to low levels of calcium found on a blood test. It can cause symptoms like tingling, muscle cramps, and heart rhythm problems that can range from mild to life-threatening. Hypocalcemia is particularly a problem for people who are hospitalized. One study found that over 20% of such people could be characterized as having hypocalcemia in addition to their other medical problems.

Symptoms

If your calcium is only a little low, you might not notice any symptoms from hypocalcemia. You are also less likely to experience symptoms if your calcium has been gradually lowered over time.

Hypocalcemia may cause symptoms such as the following:

  • Sensations of numbness or tingling
  • Muscle cramps, spasms, or weakness
  • Dry skin or other skin issues
  • Brittle nails
  • Difficulty swallowing
  • Shortness of breath and wheezing
  • Seizures
  • Heart rhythm problems
  • Cardiomyopathy
  • Fatigue
  • Mental disturbances such as anxiety and confusion

However, not everyone will experience all these symptoms. Sometimes these symptoms are relatively mild, but in other situations they may cause life-threatening problems. In someone who is already critically ill, having hypocalcemia may increase a person’s risk of death.

Causes

Understanding Calcium Regulation

Most people know that calcium is a component of your bones. But calcium is also found in your blood and inside your body’s cells. In fact, calcium is involved in many important biological processes. For example, it plays roles in blood clotting and in helping certain enzymes to function. It is also critical for proper signaling in your nerves and muscles, including your heart muscle.

Because of this, your body works to tightly regulate the amount of calcium present in your blood. If it’s too high, it tries to bring it down; if it’s too low, it tries to bring it up.

For example, if your calcium levels are too low, your parathyroid glands will normally release parathyroid hormone (PTH). This hormone works to increase your calcium in different ways, like reducing the amount of calcium released in your urine. Normally, the action of PTH brings the calcium back into a normal range. But hypocalcemia can result if something lowers your blood calcium but your body can’t respond normally to increase calcium levels. 

Underlying Causes Leading to Hypocalcemia

Hypocalcemia can have many different potential underlying causes. Because of the key role of PTH, it is not surprising that a low level of this hormone (called hypoparathyroidism) is one of the main causes of low calcium. Some of the reasons for this include injury to the parathyroid gland from surgery or radiation treatment, autoimmune disease, or a genetic disease leading to low PTH.

Low vitamin D is also another important cause of hypocalcemia. This hormone plays an important role in your body’s ability to absorb and utilize calcium. People can have low vitamin D from a number of different problems, such as:

  • Low dietary intake of vitamin D
  • Little sun exposure (as sunlight is another source of vitamin D)
  • Poor absorption of vitamin D (e.g., as a side effect of gastric bypass surgery)
  • Advanced kidney disease
  • Advanced liver disease

Problems with certain blood electrolytes can also sometimes lead to hypocalcemia. For example, abnormal levels of the electrolytes magnesium and phosphate might indirectly cause hypocalcemia. Some other less common causes of hypocalcemia include pancreatitis and cancer which has spread to the bones.

A number of drugs sometimes cause hypocalcemia as a side effect. Some of these include the following:

  • Certain drugs for osteoporosis (bisphosphonates like zoledronate)
  • Some antiepileptic drugs
  • Certain chemotherapy drugs (like cisplatin)
  • Diuretic drugs (like furosemide)
  • Proton pump inhibitors

For a variety of reasons, people who are critically ill have a higher risk of hypocalcemia. This can be due to underlying medical problems, sepsis, electrolyte problems, certain kinds of blood transfusions that affect calcium, or other factors.

Diagnosis

Various signs and symptoms might make a clinician suspect hypocalcemia. Your doctor will take a full medical history and ask you about your recent symptoms. Things like muscle cramps or pain and tingling in the fingers might make the clinician think of hypocalcemia.

A complete exam is also an important part of diagnosis. Your physician might tap you lightly at a certain place on your cheek. People with hypocalcemia may involuntarily contract their facial muscles in response.

Blood Tests

Definitive diagnosis of hypocalcemia requires a blood test for calcium. Calcium is a common blood test often performed with other tests as part of a basic metabolic panel (BMP) or a complete metabolic panel (CMP).

Calcium is usually first assessed through a total calcium blood test. This measures the calcium that is free in the blood as well as the calcium that is bound to a common protein in the blood (called albumin).

If this test is low, you might need a test of your albumin. This can help your clinician get a more accurate idea about whether your calcium level really is a problem. (Sometimes, if your albumin is low, it might mean that you don’t really have hypocalcemia, even if this was indicated on a previous test.)

Hypocalcemia is usually defined as having a corrected total serum calcium of less than 2.12 mmol/L. (“Corrected” just refers to a certain way of measuring calcium that accounts for albumin.)

But recognizing that hypocalcemia is present is only the first step. It is also critical to find the underlying reason that the person has low levels of calcium in their blood. This often requires additional testing.

Additional blood tests might include the following:

  • Phosphate
  • Magnesium
  • Creatinine
  • Alkaline phosphatase
  • Tests for different forms of Vitamin D
  • Parathyroid hormone
  • “Ionized” calcium (measures calcium not bound to albumin)
  • Complete blood count (CBC)

Depending on the context, you might also need other tests, such as urine tests for calcium, phosphate, or other electrolytes. Some people might need additional monitoring tests, like an EKG to check that their heart rhythm is OK.

Treatment

Treatment for hypocalcemia will vary based on a number of factors. These include the underlying cause and the severity of the problem.

If a person’s calcium suddenly drops very low, they will likely need to receive calcium through an intravenous (IV) line. This can bring up a person’s calcium more quickly than taking calcium orally. People receiving IV calcium need to be carefully monitored in a hospital setting. 

People who have calcium that is not as low can usually take oral calcium supplements instead. You may need to take these over a long period of time. Vitamin D is also often a key component of treatment.

Depending on the situation, you might need to take other substances important for calcium metabolism, like magnesium. Or you might need to stop taking a medication that is lowering your calcium too much. In some situations, you may need to take a new medication (like certain types of diuretics) that may be able to help you increase your calcium.

Other treatments may be necessary, depending on the circumstances. For example, you might need to get treatment for an underlying condition, like kidney or liver disease. Some people with hypoparathyroidism take a PTH replacement hormone that may help increase calcium to normal levels.

You are likely to need follow-up monitoring if you are found to have hypocalcemia. This is to check that your calcium has returned to normal and that your treatment hasn’t increased it too much. (This can cause elevated calcium, hypercalcemia, which has its own medical problems.) Your clinician will help tailor your treatment and monitoring schedule to your specific circumstances.

A Word From Verywell

It can be frightening to learn that you or a loved one has a lab test abnormality like hypocalcemia. It might represent an urgent medical problem or a situation that can be dealt with in a more relaxed fashion. Fortunately, in either case, these low calcium levels can usually be corrected. Don’t hesitate to bring all of your questions to your health care team.

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