Hypocalcaemia

Hypocalcaemia is a treatable condition that occurs when calcium levels in the blood fall below normal. While some people experience no symptoms at all, others may face serious complications affecting the nervous system and heart if left untreated.

Table of contents

• What is hypocalcaemia?
• The role of calcium in your body
• Symptoms of hypocalcaemia
• Causes of hypocalcaemia
• Who is affected by hypocalcaemia?
• Diagnosis of hypocalcaemia
• Treatment of hypocalcaemia

What is hypocalcaemia?

Hypocalcaemia is a medical condition characterized by low calcium levels in the blood serum^[1]. The normal range of blood calcium is typically between 8.5 to 10.5 mg/dL (2.12 to 2.62 mmol/L), while levels less than 8.8 mg/dL (2.1 mmol/L) are defined as hypocalcaemic^[2][3].

It is important to understand that hypocalcaemia refers to low levels of calcium in your blood, not in your bones^[1]. Most of your body’s calcium is stored in your bones, but you also need calcium in your blood for many important body functions.

The condition can be mild or severe, and it may be temporary or chronic (lifelong), depending on what causes it^[1]. Many different health conditions can cause hypocalcaemia, and it is often caused by abnormal levels of parathyroid hormone (a hormone that helps control calcium levels) or vitamin D in your body^[1].

The role of calcium in your body

Calcium is one of the most important and common minerals in your body^[1]. A 70-kilogram person has approximately 1.2 kilograms of calcium in their body, more than 99% of which is stored in bones^[3]. The calcium in your blood helps your nerves work, helps make your muscles squeeze together so you can move, helps your blood clot if you are bleeding, and helps your heart work properly^[1].

The levels of calcium in your blood and bones are controlled by two hormones called parathyroid hormone and calcitonin (a hormone that helps regulate calcium)^[1]. Vitamin D also plays an important role in maintaining calcium levels because it is needed for your body to absorb calcium^[1].

Approximately 50% of plasma calcium is in the free or ionized state, which is the biologically active form. About 40% is bound to proteins (mainly albumin), and 10% circulates bound to other substances^[3]. Clinical signs and symptoms are observed only with decreases in ionized calcium concentration^[3].

Symptoms of hypocalcaemia

People who have mild hypocalcaemia often have no symptoms at all^[1]. The symptoms of hypocalcaemia depend on how severe it is and how quickly it develops^[4].

Symptoms of mild hypocalcaemia can include^[1]:

• Muscle cramps, especially in your back and legs
• Dry, scaly skin
• Brittle nails
• More coarse hair than what is normal for you

If left untreated, over time hypocalcaemia can cause neurologic (affecting the nervous system) or psychologic (affecting the mind) symptoms, including^[1]:

• Confusion
• Memory problems
• Irritability or restlessness
• Depression
• Hallucinations

Severe hypocalcaemia (very low levels of calcium in your blood) can cause the following symptoms^[1]:

• Tingling in your lips, tongue, fingers and/or feet
• Muscle aches
• Muscle spasms in your throat that make it difficult to breathe (laryngospasm)
• Stiffening and spasms of your muscles (tetany)
• Seizures
• Abnormal heart rhythms (arrhythmia)
• Congestive heart failure

Doctors may also look for specific clinical signs. Trousseau’s sign is a test for latent tetany where inflating a blood pressure cuff above the systolic pressure for up to three minutes causes spasm of the hand^[5]. Chvostek’s sign is another test where tapping the cheekbone produces facial spasms^[5].

Causes of hypocalcaemia

There are many complex functions and factors involved with maintaining a steady level of calcium in your blood and body. Because of this, several different health conditions and disorders can cause hypocalcaemia^[1].

Most of the time, an issue with your parathyroid hormone levels and/or vitamin D levels is involved with the cause of hypocalcaemia. This is because parathyroid hormone helps control the level of calcium in your blood, and vitamin D helps your body absorb calcium^[1].

The most common cause for hypocalcaemia is iatrogenic hypoparathyroidism (low parathyroid hormone caused by medical treatment)^[5]. A low level of parathyroid hormone can occur when the parathyroid glands are damaged during thyroid gland surgery^[4]. Hypocalcaemia is a common side effect of having your thyroid removed (thyroidectomy). Approximately 7% to 49% of people have temporary hypocalcaemia after thyroidectomy^[1].

Other causes of hypocalcaemia include^[4][5]:

• Other forms of hypoparathyroidism
• Vitamin D deficiency (due to inadequate consumption or inadequate exposure to sunlight)
• Kidney failure or kidney dysfunction
• Pancreatitis
• A low level of magnesium (hypomagnesemia), which reduces the activity of parathyroid hormone
• Inadequate consumption of calcium
• Disorders that decrease calcium absorption
• Certain medications, including rifampin (an antibiotic), anti-seizure medications (such as phenytoin and phenobarbital), bisphosphonates (medicines used to treat bone conditions), calcitonin, chloroquine, and steroids

Some cancers and their treatments can also cause low blood calcium levels. After head and neck surgery for cancer, you could have permanently low calcium levels, but they could also go back to normal after a few months^[6].

Who is affected by hypocalcaemia?

Hypocalcaemia can affect people of all ages, including infants^[1]. The age at which someone could develop hypocalcaemia usually depends on the cause. For example, if an infant has hypocalcaemia, it is often because of a genetic disorder^[1].

In infants, hypocalcaemia is more common in premature and low birthweight babies because their parathyroid glands are less mature. It may also occur in babies who have a difficult birth or whose mothers have endocrine disorders, such as diabetes or elevated serum levels of calcium^[7].

Healthcare professionals and researchers have not yet determined exactly how common hypocalcaemia is. This is likely because hypocalcaemia is usually a side effect of other health issues^[1]. About 18% of people who are being treated in hospital have hypocalcaemia^[5].

Diagnosis of hypocalcaemia

Hypocalcaemia is often detected by routine blood tests before symptoms become obvious^[4]. Doctors measure the total calcium level (which includes calcium bound to albumin) and the albumin level in blood to determine whether the level of unbound calcium is low^[4].

Because the majority of body calcium is bound to albumin, total calcium should always be corrected for albumin level before the diagnosis of hypocalcaemia is made. There is an approximately 0.8 mg/dL drop in serum total calcium concentration for every 1 g/dL reduction in the serum albumin concentration^[2].

The most accurate way to measure calcium is to check the ionized calcium level, which measures the biologically active calcium. The normal range is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L)^[2].

Blood tests are also done to evaluate kidney function and to measure magnesium, phosphate, parathyroid hormone, and vitamin D levels. Other substances in blood may be measured to help determine the cause^[4].

A 12-lead electrocardiogram should be performed as there is a significant likelihood of QT prolongation, and cardiac monitoring may be required^[3]. Specific changes may also be seen on an electrocardiogram (ECG), including ST segment prolongation^[3].

Treatment of hypocalcaemia

The treatment of hypocalcaemia depends on the cause, the severity, the presence of symptoms, and how rapidly the hypocalcaemia developed^[12].

Calcium supplements, given by mouth, are often all that is needed to treat hypocalcaemia. If a cause is identified, treating the disorder causing hypocalcaemia or changing medications may restore the calcium level^[4].

For mild hypocalcaemia (serum adjusted calcium 1.9 to 2.2 mmol/L and no symptoms), treatment typically involves oral calcium supplements. One example is calcium carbonate tablets, which should be adjusted to the patient’s individual requirements^[15]. You may also be given vitamin D, because you need it to absorb calcium^[4].

If vitamin D levels are low, oral vitamin D supplementation should be started^[15]. If the patient has low magnesium levels (hypomagnesemia), this should be corrected first, as it is difficult to effectively treat hypocalcaemia in patients with concurrent magnesium deficiency^[12].

For severe hypocalcaemia (serum adjusted calcium less than 1.9 mmol/L and/or symptomatic), this is a medical emergency^[15]. Treatment involves giving calcium directly into the blood through a drip (intravenous infusion)^[4]. Initially, calcium gluconate 10% is given intravenously over 10 minutes, with ECG monitoring. This can be repeated until the patient is without symptoms. This is followed by a continuous intravenous infusion, with the rate adjusted to achieve normal calcium levels^[15].

After your doctor has your calcium levels up, be sure to get plenty of calcium in your diet. Eat foods rich in calcium, including yogurt, cheese, milk, and dark green vegetables. This is the best way to get the calcium you need. You can get vitamin D from eggs, fatty fish, soft margarine, and milk^[17].

If you have a kidney or parathyroid problem, you may need to keep taking extra calcium^[17]. Follow-up care is a key part of your treatment and safety^[17].