What is sodium test?

Sodium test, also known as Na test, his generally done as a part of the basic metabolic panel or electrolyte panel to measure sodium levels in blood and urine. Sodium is an electrolyte, which plays a vital role in the normal functioning of body cells, nerves and muscles. It also helps in maintaining fluid balance in body. 

Sodium is most commonly consumed in the form of salt and kidneys are responsible for eliminating all the excess sodium from the body. However, in the case of excess sodium intake or damaged kidneys, your body cannot throw out this electrolyte. As a result, it starts accumulating in blood, leading to a condition called hypernatremia. Hypernatremia may also occur due to excessive loss of fluids from body, such as in diarrhoea or vomiting. It may cause water retention in the body, leading to high blood pressure.

On the other hand, excessive intake of fluids or problems with urination may lead to abnormally low levels of sodium, also called hyponatremia.

  1. Why is sodium test performed?
  2. How do you prepare for sodium test?
  3. How is sodium test performed?
  4. Sodium test results and normal range

A sodium blood test is recommended in individuals experiencing the following symptoms:

A sodium blood test is also ordered in individuals on sodium therapy and diuretic therapy.

A sodium urine test is suggested in case abnormal levels of sodium are detected in the blood test. It helps:

  • To identify kidney damage
  • To diagnose the presence of any medical condition that may affect your health
  • To check the levels of salt intake in individuals with high blood pressure
  • To evaluate the effects of the treatment employed for the management of sodium levels
  • To assess sodium levels in individuals with vomiting and diarrhoea

No special preparations are needed for a sodium blood test, but your doctor may tell you to stop taking certain medications that may interfere with test results. Some of these medications include antidepressants, antibiotics, diuretics, non-steroidal anti-inflammatory drugs, antihypertensive medications and lithium. Under no circumstances should any medication be stopped without consulting the doctor.

In the case of sodium urine test, you'll be asked to drink plenty of water before giving the urine sample. Also, the doctor should know about any herbs, vitamins and supplements if you are taking any as these may affect test results.

Sodium blood test: For this test, a blood sample will be collected from a vein in your arm with the help of a needle. It may cause moderate pain and pricking or stinging sensation at the site of injection. Slight bruising may also be observed at the needle insertion site. Though, it will subside on its own. Some other risks involved in blood collection include excessive bleeding, light-headedness, blood accumulation under the skin (hematoma) and infection.

Sodium urine test: Urine sample will have to be collected in a container as per the instructions given by the doctor.

Test results of a sodium test may vary based on individual age, sex, and medical history, and testing methods.

Normal results:

Normal sodium levels in the bloodstream are usually between 136 to 145 mmol/L. The normal level of sodium for a one-time urine sample is 20 mEq/L.

Abnormal results:

Abnormal levels of sodium in the blood indicate various conditions.

Hypernatremia or higher than normal sodium levels occur due to:

  • Excessive salt or bicarbonate intake in the diet
  • Diabetes insipidus, in which, kidneys are not able to conserve water
  • Dehydration

Hyponatremia or lower than normal sodium levels occur due to:

  • Excessive sodium or electrolyte loss due to vomiting, diarrhoea, kidney disease
  • Liver or kidney disease
  • Excessive use of diuretics

Abnormal levels of sodium in the urine may be due to:

  • Excess salt intake
  • Thyroid conditions
  • Diseases of kidneys, heart or liver
  • Medications like diuretics
  • Dehydration
  • Diseases that affect sodium levels

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor. 

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  1. University of Rochester Medical Center Rochester, NY. [Internet] Sodium (Blood)
  2. Appalachian Regional Healthcare System. Sodium blood test. Watauga Medical Center, USA. [internet]
  3. Guillaumin J, DiBartola SP. Disorders of Sodium and Water Homeostasis. Vet Clin North Am Small Anim Pract. 2017 Mar;47(2):293-312. PMID: 28017410
  4. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Sodium Blood Test
  5. Costas A Anastasiou et al. Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss . J Athl Train. 2009 Mar-Apr; 44(2): 117–123. PMID: 19295955
  6. Rebecca M Reynolds et al. Disorders of sodium balance . BMJ. 2006 Mar 25; 332(7543): 702–705. PMID: 16565125

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