What to Know About Hypocalcemia and Tetany

Medically Reviewed by Dan Brennan, MD on June 29, 2021
4 min read

Hypocalcemia is closely linked with vitamins and minerals like magnesium and vitamin D and is one of the main causes of tetany.

Hypocalcemia is a condition where you have low calcium levels in your blood. It can be an inherited disorder or it can be caused by other conditions.

Calcium is a critical mineral for your bone and teeth integrity and health. It also acts as a messenger for other functions in your body — it plays a role in blood vessel tightening and relaxation, nerve impulses, blood clotting, and muscle contractions.

It works very closely with hormones like calcitonin and parathyroid hormone as well as vitamin D, which all impact your bone health. Your cells also have calcium channels that open to let calcium in or out, which is important for muscle contractions, including your heart muscles.

Your body normally tightly controls your calcium levels, but low calcium levels are common.

There are three main groups of hypocalcemia causes.

Parathyroid hormone deficiency. Your parathyroids are small glands on the back of your thyroid that release the parathyroid hormone. This hormone controls calcium levels between your blood and bones. Without enough parathyroid hormone, your calcium levels can drop.

The parathyroid glands can become damaged from thyroid surgery or from autoimmune disease — where your immune system attacks your glands or the proteins that sense calcium.

High parathyroid hormone. Sometimes your parathyroid can release too much parathyroid hormone, which can cause calcium problems. High levels can be caused by:

  • Chronic kidney disease
  • Not enough vitamin D — because you did not get enough sunlight or have kidney or liver disease
  • Pseudoparathyroidism — a genetic condition that makes your body resistant to the parathyroid hormone
  • Idiopathic pseudoparathyroidism — where the parathyroid glands are missing or are wasting away

Other causes. There are several other causes of hypocalcemia, including:

  • Alkalosis — where your blood is too alkaline and causes low calcium levels
  • Massive blood transfusion with blood that’s been clotted with calcium citrate — which causes your calcium to bind with calcium citrate
  • Pancreatitis — which is inflammation of your pancreas that causes calcium to deposit in your abdomen
  • Low magnesium levels
  • Some medications like phenobarbital, phenytoin, or rifampin
  • Poor nutrition

Tetany is a condition that causes involuntary muscle contractions and changes in your brain cells. Some people don’t have any symptoms, but it can be life-threatening for others.

Symptoms of tetany include:

  • Muscle spasms
  • Laryngospasm — which causes muscle spasms in your vocal cords, making speaking and breathing difficult
  • Numbness in your hands and feet
  • Seizures
  • Heart problems
  • Carpopedal spasm, a hand spasm when your blood pressure is taken

Tetany usually is caused by low calcium levels, and hypoparathyroidism that causes low calcium levels also causes long term tetany.

Hypocalcemia may happen without any symptoms or it may become life-threatening. Many of its symptoms are similar to those of tetany. These include:

  • Seizures
  • Numbness and tingling
  • Anxiety
  • Depression
  • Very strong emotions that change quickly
  • Chvostek’s sign — a facial spasm when the nerve along your jaw is tapped
  • Unexplained dementia
  • Dry, scaly skin
  • Brittle nails
  • Coarse hair
  • Yeast infections

Sometimes your doctor might find hypocalcemia while doing tests for other things. If you don’t have any symptoms, you might not know.

If your doctor suspects you have low blood calcium levels, they’ll order some blood tests to check for:

  • Ionized calcium
  • Magnesium
  • Parathyroid hormone
  • Phosphate
  • Alkaline phosphatase
  • Vitamin D

Hypocalcemia is diagnosed when your total blood calcium is less than 8.8 milligrams per deciliter or 2.2 millimoles per liter or when your blood ionized calcium is less than 4.7 milligrams per deciliter or 1.17 millimoles per liter.

Treatment for hypocalcemia depends on its cause and sometimes its symptoms.

For tetany caused by hypocalcemia, the treatment is an intravenous dose of calcium gluconate. You might have a quick change in your symptoms, but it might not last very long. Sometimes you might need a few more doses over 12 to 24 hours.

For hypoparathyroidism, your doctor will give you calcium gluconate or calcium carbonate pills. Depending on how severe your hypocalcemia is, you might need high doses until your levels normalize. If you don’t respond to this treatment, you might need parathyroid hormone medication.

For long term hypocalcemia, your doctor will prescribe calcium pills along with vitamin D. If you have chronic kidney disease, you might need to take phosphate, too.

Many people have hypocalcemia and tetany and don’t know and others have mild forms. In some severe cases, both conditions can be life-threatening. If you have symptoms of low calcium, talk to your doctor.