High calcium in the blood is also known as hypercalcemia. Calcium is an important electrolyte, or charged mineral, for many processes in the body, especially nerve and muscle tissues function. Albumin is a protein that helps to carry calcium in the blood. Its levels need to be measured along with the calcium level in order to determine how much calcium is available to the rest of the cells. High blood calcium can cause problems for the cells and lead to fatigue, weakness, constipation, nausea, bone pain, depression and confusion.
Calcium in the Blood
Calcium exists in two states in the blood -- bound and free. Since calcium carries a positive charge, it binds to the negative charges on proteins in the blood. The negative charges on albumin are the primary sites that bind calcium. The rest of the calcium is free in the fluid component of blood. The measure of the bound and free calcium together is the total calcium. The free calcium not bound by albumin is the important calcium level, because this calcium is available for processes such as nerve transmission and muscle contraction. High calcium in the blood can therefore refer to a high total calcium or high free calcium.
Many labs report the total calcium, although the free, or ionized calcium, can usually be measured by special request. However, since calcium binds avidly to albumin, you can calculate the level of free calcium if the total calcium and albumin levels are known. More specifically, each 1 g/dL decrease of albumin will decrease 0.8 mg/dL in measured serum calcium. Thus, 0.8 must be added to the measured calcium to get a corrected calcium value.
The most common causes of high blood calcium are different for mildly ill people in an outpatient setting versus sicker people in the hospital. When people come to an outpatient office with high blood calcium, it is most often caused by hyperparathyroidism. In this condition, the parathyroid glands in the neck are over-active and cause the bones to release calcium into the blood, the kidneys to retain calcium from urine, and intestine to increase the absorption of calcium from the intestine. In a hospital setting, cancer is the most common cause of high blood calcium. Symptoms of high calcium can include weakness, apathy, constipation, nausea and other problems.
Diagnosis and Treatment
The symptoms of high calcium and an abnormal albumin are not specific to any one disease, so the diagnosis involves a meticulous process. A detailed medical history, including symptoms, family history, habits such as smoking and consideration of medications used helps to narrow the possibilities. This is followed by a physical exam. Problems such as changes to muscular reflexes may be present in hypercalcemia. More definitive diagnosis is established by laboratory examination of the blood, which can reveal high calcium and high or, more likely low, albumin levels. Depending on these findings, other lab tests, such as for parathyroid hormone, or imaging to look for a tumor, may be performed. The treatment of hypercalcemia generally involves IV fluid administration and diuretics to increase the urine output, as well as addressing the underlying condition. Low albumin itself is usually not treated unless extreme, at which point intravenous albumin may be given, but that approach is controversial.
- “Harrison’s Principles of Internal Medicine”; Anthony S Fauci, et al.; 17th Ed 2008
- “Robbins and Cotran Pathologic Basis of Disease”; Vinay Kumar, et al.; 8th Ed 2009
- “Henry's Clinical Diagnosis and Management by Laboratory Methods”; Richard A. McPherson, et al.; 21st Ed 2006