Blood Sodium Test

sodium blood test

Last Updated December 20th, 2021

What is a blood sodium test?

A blood sodium test measures the amount of sodium (an important electrolyte) in your body. It is also sometimes referred to as serum sodium test.

What is the role of sodium in my body?

Sodium is an essential nutrient involved in the preservation of normal cellular homeostasis. It performs the following chief functions-

– It aids in the regulation of fluid and electrolyte balance in your body.

– It plays an important part in maintaining blood pressure.

– It is critical for maintaining ECF (extracellular fluid) volume due to its osmotic properties.

– It is vital for the optimum functioning of muscle and nerve cells.

– It is essential for the transport of nutrients across plasma membranes.

You get most of the sodium from your diet; the body requires only 1-2 mmol of sodium per day. The excess of sodium is excreted by the kidneys under the directive of body hormones, aldosterone ( a hormone released by the adrenal gland) being the most important.

Why has my physician asked me to undergo a sodium test?

Your physician may have ordered a sodium test for you if you are showing signs of either hypernatremia or hyponatremia.

Hypernatremia– a hyperosmolar state defined as sodium levels in your blood (in excess of 145 mEq/L). The signs of hypernatremia include-

– Excessive thirst
– Asthenia
– Loss of sleep
Tachycardia (increased heartbeat)
– Decreased frequency of urination
– Peripheral swelling
– Vomiting
– Diarrhea
– Hyperreflexia
– Coma (in extreme cases)

Hyponatremia is defined as decreased sodium levels in your blood (below 135 mEq/L). The signs of hyponatremia include-

– Headache
– Fatigue
– Confusion
– Muscle spasms
– Seizures
– Vomiting
– Irritability
– Loss of consciousness (in extreme cases)

What are the reasons of hypernatremia?

Hypernatremia is commonly observed in the geriatric age group, young children and bedridden patients. The factors leading to an excess of sodium in your body include-

– Drug-induced- steroids, laxatives, oral contraceptive pills, lithium, certain pain medications
– Inadequate water intake
– Secondary to hormonal disorders- high levels of aldosterone or cortisol/low levels of vasopressin
– Excessive intake of salty food/water
– Severe sweating/diarrhea
– Diabetes insipidus

What are the causes of hyponatremia?

Hyponatremia is not seen in young healthy adults. It is basically a disease of older adults.

– Drug induced- diuretics, antidepressants, carbamazepine, non-steroidal anti-inflammatory drugs
– Use of recreational drug Ecstasy (3,4-methylenedioxy-N-methamphetamine)
– Liver/kidney diseases
Cardiac failure
– Severe burns
– Hormonal imbalance-high levels of antidiuretic hormone/low levels of thyroid/adrenal insufficiency
– Severe vomiting/diarrhea/sweating
– Intake of excess amount of water

How should I prepare for the sodium test?

No specific preparation is required. You need to discuss with the physician your medical history. As sodium test is a blood test and involves the standard techniques of venipuncture, you need to inform your physician if-

– You are taking any blood thinners
– You are suffering from any coagulopathy
– You should also inform your physician about the medications (including ayurvedic, homeopathic and natural remedies) that you might be consuming. The levels of sodium in your blood can be altered by a variety of medicines.

Do I need to fast before a sodium test?

There is no need to fast before a sodium blood test. You can consume normal meals before this test. However, you should consult your physician if he has ordered other diagnostic tests along with the sodium test which may require you to fast overnight.

Can I undergo a sodium test if I am pregnant?

Yes, it is perfectly safe to undergo a sodium test if you are pregnant or breastfeeding your child.

Can children undergo a sodium test?

Yes, children of all ages can undertake a sodium test as it is a safe, risk free and easy to perform procedure.

What are the risks involved?

A sodium test is a blood test. It is easy to perform, safe and quick test. Complications are rarely seen. However, as this test involves the puncture of a vein to collect a blood sample, the following complications may arise-

You may feel a stinging sensation when the needle pricks your skin. The perception of pain varies in different patients.

The act of puncturing a vein and drawing blood may be scary for some. You may feel lightheadedness at the sight of blood. It is advisable to distract yourself during this step if you are faint-hearted.

A bruise at the sight of the prick may appear. You can prevent it by pressing on the site of the prick for a few minutes.

In some cases, bleeding may be encountered at the site of venous invasion.

A hematoma may form at the site of puncture.

There are chances of infection at the site of venesection at a later stage. If you encounter the presence of pus or signs of inflammation (phlebitis) at the site, consult your physician.

What are the contraindications of a sodium test?

There are no absolute contra-indications to a sodium test. However, as it is a blood test including venesection, your physician may defer performing this test if you suffer from a bleeding tendency.

How is a sodium test performed?

A sodium test is rarely performed as a stand-alone test. It is normally a part of the “electrolyte tests”. It is a blood test carried out on an outpatient basis unless the patient is already admitted to a hospital. The standard technique of venipuncture is employed. The few simple steps are as follows-

– You will be escorted to an area dedicated to collecting samples.

– You will be asked to sit on a comfortable chair or lie down on a hospital bed.

– The technician will apply a tourniquet proximally to the site chosen for venipuncture. This makes the veins more prominent, allowing easier access.

– The area is cleaned with a disinfectant.

– A sterile needle is used to puncture the vein and draw about 5 ml of blood.

– The pressure is applied to the vein with sterile gauze after the needle is withdrawn and the tourniquet is released.

– The blood sample is collected in a vial.

How long does the procedure last?

The entire procedure is over in 5-10 minutes. In obese patients, patients belonging to geriatric age group and very young children, venous access is sometimes difficult, leading to more than one prick.

When can I get the results of my test?

The results of a blood sodium test can be obtained the very same day-within 24 hours of conducting the test.

How are the disorders of blood sodium concentration treated?

Hypernatremia– The treatment of hypernatremia is essentially directed at replacing the intravascular volume and free water (per oral/intravenous). The pace of replacement is guided by the rate at which hyponatremia develops.

Hyponatremia is said to be acute if it develops within 24 hours and chronic if it takes longer. During replacement, the levels of other electrolytes need to be monitored. Moreover, the offending drug or the underlying condition which led to this condition needs to be treated.

Hyponatremia-The treatment of hyponatremia is also directed at correcting the blood sodium level. The urgency to correct the imbalance is decided by the degree, duration and clinical features of the condition. A general principal followed is correcting the deficit slowly—by ≤ 8 mEq/L over 24 h. Additionally, the offending drug or the underlying condition which led to this condition needs to be treated.

What is the cost of conducting a sodium test in India?

The cost of a sodium blood test in India ranges from Rs 250-750; the actual cost varies depending on the city that you live in.

What other tests are usually performed alongside a sodium test?

Though blood sodium estimation is a routinely performed test, it is rarely carried out alone. It is mostly a part of a set of tests measuring the vital body electrolytes and other substances. The parameters measured along with a sodium test may include-

– Serum potassium test
Serum chloride test
– Serum bicarbonate test
– Urine sodium test
– Serum urea test
– Serum uric acid test
– Anion gap test


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