Sodium Test

Other names: Na

Sodium is an electrolyte, which is essential for effective body function. Sodium has various important roles in the body, including regulating the amount of water in the body and controlling blood pressure. The body tries to control the amount of sodium in the blood by keeping it within a very tight target range; it does this by producing hormones that either increase or decrease the loss of sodium in the urine, producing hormones that prevent water loss and regulating thirst.

When levels of sodium in the body change, the levels of water in the body also change.

When is the test used?

The test is used to measure the levels of sodium in the body; abnormal sodium levels can cause health problems. Abnormal levels of sodium may be caused by many different health conditions, including problems with the liver, kidneys, lungs, thyroid glands or adrenal glands.

The test is usually carried out alongside other electrolyte tests and it may be ordered as a routine test for people with non-specific symptoms. Electrolyte tests may also be ordered to monitor the condition of patients who are receiving treatment for conditions including liver and kidney disease, heart disease and high blood pressure.

How is the test carried out?

The test is performed by collecting and analysing a sample of blood from a vein in the arm; a needle in inserted into the vein and the blood is drawn out using a syringe. Once the sample has been collected, the blood will be bottled, labelled with the patient’s name and sent to the laboratory for testing.

A urine sample may also be ordered.

What do the test results show?

Abnormal sodium levels are usually caused by a disruption with the systems used by the body to control the level of sodium in the body. Low levels of sodium in the blood usually indicate that there is a problem with the regulation of water loss, water retention and fluid build-up; this may contribute to symptoms such as oedema. Low levels of sodium are very rarely caused by insufficient intake of sodium through the diet; instead they are usually due to dehydration, persistent sickness or diarrhoea, excessive sweating or health conditions which affect the adrenal glands or the kidneys. Diuretic medications may also cause low sodium levels.

High levels of blood sodium are usually caused by dehydration; this usually contributes to symptoms including dry mouth, dry eyes, thirst, irritability, restlessness and convulsions.

Trauma or surgery may affect sodium levels; levels may increase because blood flow to the kidneys is decreased.

Specific Blood Tests

Blood Test Guide

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