A blood calcium test is ordered to screen for, diagnose, and monitor a range of conditions relating to the bones, heart, nerves, kidneys, and teeth. Blood calcium levels do not directly identify how much calcium is in the bones, but rather, how much calcium is circulating in the blood.


Blood chloride testing is often ordered, along with other electrolytes, as part of a regular physical to screen for a variety of conditions. These tests may also be ordered to help diagnose the cause of signs and symptoms such as prolonged vomiting, diarrhea, weakness, and respiratory distress. If an electrolyte imbalance is detected, the doctor will look for and address the disease, condition, or medication causing the imbalance and may order electrolyte testing at regular intervals to monitor the effectiveness of treatment. If an acid-base imbalance is suspected, the doctor may also order blood gas tests to further evaluate the severity and cause of the imbalance.


CO2 levels in the blood are affected by kidney or lung functions. It may also indicate a very high blood sugar and other conditions. Your care provider will need to evaluate if this test is out of normal ranges.


A magnesium test is used to measure the level of magnesium in the blood. Abnormal levels of magnesium are most frequently seen in conditions or diseases that cause impaired or excessive excretion of magnesium by the kidneys or that cause impaired absorption in the intestines. Magnesium levels may be checked as part of an evaluation of the severity of kidney problems and/or of uncontrolled diabetes and may help in the diagnosis of gastrointestinal disorders.

Phosphorous, Inorganic

Phosphorus tests are most often ordered along with other tests, such as those for calcium, parathyroid hormone (PTH), and/or vitamin D, to help diagnose and/or monitor treatment of various conditions that cause calcium and phosphorus imbalances.


Potassium testing is frequently ordered, along with other electrolytes, as part of a routine physical. It is used to detect concentrations that are too high (hyperkalemia) or too low (hypokalemia). The most common cause of hyperkalemia is kidney disease, but many drugs can decrease potassium excretion from the body and result in this condition. Hypokalemia can occur if you have diarrhea and vomiting or if you are sweating excessively. Potassium can be lost through your kidneys in urine; in rare cases, potassium may be low because you are not getting enough in your diet.

Sodium, Serum

Blood sodium testing is used to detect hyponatremia or hypernatremia associated with dehydration, edema, and a variety of diseases. Your doctor may order this test, along with other electrolytes, to screen for an electrolyte imbalance. It may be ordered to determine if a disease or condition involving the brain, lungs, liver, heart, kidney, thyroid, or adrenal glands is causing or being exacerbated by a sodium deficiency or excess. In patients with a known electrolyte imbalance, a blood sodium test may be ordered at regular intervals to monitor the effectiveness of treatment. It may also be ordered to monitor patients taking medications that can affect sodium levels, such as diuretics.