Sodium is an electrolyte present in all body fluids and is vital to normal body functions, including nerve and muscle function. It helps cells function normally and helps regulate the amount of fluid in the body. A sodium blood test is used to detect abnormal concentrations of sodium, including low sodium (hyponatremia) and high sodium (hypernatremia). This is often done as a part of an electrolyte panel or a basic metabolic panel during a routine health checkup. A blood sodium test may also be used to detect the cause and help monitor treatment in people with dehydration, excess fluid (edema), or with a variety of symptoms such as:
- Dry mucous membranes
In addition, blood sodium can be abnormal in many diseases. A healthcare professional may order this test, along with other electrolytes, to identify an electrolyte imbalance or if there are symptoms of illness involving the brain, lungs, liver, heart, kidney, thyroid, or adrenal glands. In people with a known electrolyte imbalance, a blood sodium test may be used to monitor the effectiveness of treatment or to monitor people taking medications that can affect sodium levels, such as diuretics. In addition, electrolyte panels and basic metabolic panels are commonly ordered on a regular basis when monitoring treatment of certain conditions, including high blood pressure, heart failure, and liver / kidney disease.
A low blood sodium level, called hyponatremia, is usually caused by losing too much sodium. This is commonly due to conditions such as:
- Excessive sweating
- Severe vomiting / diarrhea
- Drinking too much water
- Use of diuretics
A low blood sodium level can also be caused by excess fluid accumulation in the body (edema), which can be due to:
- Heart failure
- Kidney disease
- Cystic fibrosis
A high blood sodium level, called hypernatremia, is almost always caused by a high-sodium diet or by not drinking enough water and being dehydrated. Dehydration may be caused by:
- Medicines (such as diuretics)
- Severe vomiting or diarrhea
- Cushing’s syndrome
- Kidney disease or injury
- Diabetic ketoacidosis
- Diabetes insipidus, a condition that makes it hard to balance water level in the body.
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