Normal and Abnormal Calcium Levels

Hi, I'm Dr. Masha Livhits, an endocrine surgeon at UCLA. A common reason that patients come to see us at the UCLA Health Endocrine Center is a high calcium level on a blood test. Our job is to help figure out why the calcium level is high and what we can do to correct it.

Let's take a moment to delve into the topic of calcium levels in the body. When you undergo a routine blood test as part of your annual physical examination with your healthcare provider, it typically includes an assessment of your calcium levels as part of a chemistry panel.

The normal range for blood calcium levels is 8.5 to 10.4 mg/dL, with some variation between different laboratories. Medications (most often diuretics such as furosemide/Lsix and hydrochlorothiazide) and certain health conditions (most often nephrotic syndrome, kidney disease, and malnutrition) can alter the normal range for calcium in some individuals.

Maintaining optimal calcium levels is crucial for various physiological functions, including bone health, muscle contraction, nerve transmission, and blood clotting. Abnormalities in calcium levels, whether too high (hypercalcemia) or too low (hypocalcemia), can lead to various health issues and may require further evaluation and management by your healthcare provider.

Regular monitoring of calcium levels as part of routine blood tests helps healthcare providers assess overall health and identify any potential imbalances or abnormalities early on. This proactive approach enables timely intervention and appropriate management to maintain optimal calcium homeostasis and support overall well-being.

Assessment of the total blood calcium level is generally the most accurate method for evaluating calcium levels. Roughly half of the calcium in your bloodstream is bound to proteins. The total blood calcium level measures both bound and free (ionized) calcium together. Individuals with malnutrition or kidney disease may have low blood protein levels, which will lower the total blood calcium level. In such cases, it may be more accurate to conduct a test known as ionized calcium. This test measures the amount of calcium in the blood that is free (not bound to proteins).

What if your calcium level is high?

The finding of an elevated blood calcium level should prompt a thorough investigation to identify the underlying cause. Initially, if a high calcium level is detected, it's standard practice to recheck the measurement to rule out any potential laboratory errors or transient fluctuations. If the calcium level remains elevated upon retesting, further diagnostic tests are warranted to pinpoint the underlying cause.

At our center, a calcium level exceeding 10.4 milligrams per deciliter (mg/dL) is considered high. Patients with elevated calcium levels undergo additional evaluations to determine the underlying etiology. One common condition associated with high calcium levels is primary hyperparathyroidism, characterized by overactivity of the parathyroid glands, which regulate calcium levels in the body. Primary hyperparathyroidism is the leading cause  of high blood calcium levels, accounting for >90% of cases.

Diagnostic assessments for hyperparathyroidism typically involve measuring blood levels of parathyroid hormone (PTH). Elevated PTH levels, along with high calcium levels, support the diagnosis of hyperparathyroidism. Additional tests, such as imaging studies like ultrasound or sestamibi scans, may be conducted to localize any abnormal parathyroid glands.

Other potential causes of high calcium levels include certain medications, such as thiazide diuretics or lithium, underlying medical conditions like hyperthyroidism, adrenal gland disorders, or malignancies affecting the bones or parathyroid glands.

High calcium levels, also known as hypercalcemia, can lead to various symptoms, including excessive thirst, frequent urination, abdominal pain, bone pain, muscle weakness, fatigue, and confusion. If left untreated, severe hypercalcemia can result in serious complications such as kidney stones, osteoporosis, or cardiac arrhythmias.

Management of high calcium levels focuses on addressing the underlying cause. Treatment may involve lifestyle modifications, discontinuation of offending medications, dietary adjustments, hydration, and, in some cases, surgical intervention to remove abnormal parathyroid glands. Close monitoring and ongoing management by healthcare providers are essential to ensure optimal management of high calcium levels and prevent potential complications.

What happens if your calcium level is low?

If your calcium level is low, you may have vitamin D deficiency, trouble absorbing calcium in your diet, or kidney problems.

When calcium levels in the body are low, it can indicate various underlying issues that warrant attention. Vitamin D deficiency is a common cause of low calcium levels, as vitamin D plays a crucial role in calcium absorption from the intestines. Inadequate exposure to sunlight, insufficient dietary intake of vitamin D-rich foods, or conditions impairing the body's ability to metabolize vitamin D can lead to deficiencies.

Furthermore, difficulties in absorbing calcium from the diet can contribute to low calcium levels. Conditions such as inflammatory bowel disease, celiac disease, or certain medications can hinder the absorption of calcium in the gastrointestinal tract, leading to decreased levels in the bloodstream.

Kidney problems can also lead to low calcium levels. The kidneys play a vital role in regulating calcium balance in the body by filtering excess calcium from the bloodstream and excreting it in the urine. However, conditions like chronic kidney disease or renal failure can impair this regulatory function, resulting in decreased calcium levels in the blood.

Low calcium levels, also known as hypocalcemia, can manifest in various symptoms, including muscle cramps, numbness or tingling in the extremities, fatigue, and irregular heart rhythms. If left untreated, severe hypocalcemia can lead to more serious complications such as osteoporosis, seizures, or cardiac arrhythmias.

Therefore, if you experience symptoms suggestive of low calcium levels or have risk factors predisposing you to calcium deficiency, it's important to consult with your healthcare provider for proper evaluation and management. Treatment of low calcium levels may involve addressing underlying causes, dietary modifications, supplementation with calcium and vitamin D, and in some cases, medication or other interventions to improve calcium absorption and balance in the body.

Key Insights:

  • Calcium levels are typically measured as the total amount of calcium in the blood, which includes both protein-bound and free calcium. Poor nutrition or kidney disease can affect total blood calcium levels.
  • If a high calcium level is detected, the next step is to recheck the level to rule out any lab errors. Persistent high blood calcium levels require further investigation to determine the underlying cause.
  • Low calcium levels may be caused by vitamin D deficiency, difficulties in absorbing calcium from the diet, or kidney problems. Identifying the underlying cause is important for appropriate treatment.
  • A calcium level above 10.4 mg/dL is considered high and indicates the need for assessing the parathyroid hormone (PTH) level. Primary hyperparathyroidism is the most common cause of high blood calcium levels, explaining more than 90% of cases.

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