What is Hypocalcemia? - Causes, Symptoms & Treatment

Instructor: Brenda Ware
Hypocalcemia is an electrolyte imbalance that affects the function of the nerves and the muscles. Read more about this imbalance, its various causes, effects on the body, and treatments. Challenge your knowledge with a quiz.

A nurse is assessing an 80-year-old patient with a history of alcoholism, kidney failure, and a hip fracture, who had surgery to remove their thyroid gland. As part of the assessment, the nurse observes for any evidence of hypocalcemia. What is hypocalcemia? Why is this patient at risk for this problem?


Hypocalcemia is an electrolyte imbalance in which the serum, or blood, calcium level is below the normal range. The normal serum calcium level is 8.5-10.5 mg/dl.


The patient above is at risk for hypocalcemia for several reasons. First, the patient's thyroid gland has been removed. The thyroid gland is located in the neck. Its main function is to regulate metabolism. It also secretes calcitonin, which is a hormone that plays a role in normalizing calcium levels that are too high. But, more importantly, located on the back of the thyroid gland are two small parathyroid glands.

The parathyroid glands secrete parathyroid hormone (PTH). PTH directly regulates serum calcium levels. When PTH levels are low, so are serum calcium levels. Surgical procedures, diseases, tumors, or injuries to the neck can affect the parathyroid gland. Surgeons attempt to preserve or relocate the parathyroid glands whenever possible during thyroid surgery.

The patient is also at risk for hypocalcemia because of the diagnosis of kidney failure. The kidneys play a major role in the regulation of serum calcium levels by metabolizing a hormone known as Vitamin D. Vitamin D is ingested in food and synthesized by the skin from ultraviolet rays. It is converted to an active form by the kidneys and then released into the gastrointestinal system to facilitate calcium absorption into the blood. Dysfunctional kidneys hinder this conversion.

Kidney failure can also prevent the excretion of phosphate, which is excreted through urine. As the kidneys fail, urine production is diminished, which can result in the accumulation of phosphate molecules in the blood. The phosphate molecules bind with the available calcium molecules and deposit the calcium in the skin and organs, making them unavailable in the blood for functional use. The higher the phosphate level, the lower the serum calcium level.

Lastly, this patient has a history of alcoholism. Low magnesium levels are often seen in people with chronic alcoholism due to nutritional and absorption deficits. Magnesium is an electrolyte that stimulates the release of the PTH. Magnesium deficits can hinder the secretion of PTH, resulting in lower calcium levels.


A balance between calcium and sodium molecules is required for nerve stimulation, muscle contraction, and muscle relaxation. Hypocalcemia causes the nerves to be in a persistent state of stimulation and the muscles to be in a persistent state of contraction. When prolonged, this can result in a state known as tetany. To look for signs and symptoms of hypocalcemia, the nurse closely assesses the respiratory, nervous, musculoskeletal, and cardiac systems.

First, the nurse assesses respiratory status by observing for any signs of difficulty breathing and listening to lung sounds. The nurse is listening for a high-pitched sound known as stridor. Stridor is the result of spasms of the muscles of the larynx (voice box). The spasms can narrow the airway or cause complete closure, resulting in the inability to inhale air, and suffocation. This is a medical emergency that requires immediate intervention to support breathing and prevent death.

Secondly, the nurse assesses the cardiac system. The nurse may palpate, or examine by touch, a low heart rate or hear abnormal or irregular heart sounds. The nurse monitors the electrocardiogram for abnormal heart rhythms, which indicate that the heart is not relaxing between beats.

Next, the nurse assesses the nervous system by asking the patient if he or she is having any numbness or tingling of the hands or around the mouth. If the hypocalcemia is prolonged, the patient may experience seizures.

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