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Serum Electrolyte

Interpreting Results
Tests Included
Serum Electrolyte

Overview of Serum Electrolyte

What is Serum Electrolyte?

Electrolytes are minerals which are present in the blood and body tissues. They are essential for metabolism, for proper nerve and muscle functioning, for maintenance of proper water balance, and proper blood pH (acid-base balance). The serum electrolyte test includes a group of tests to measure the following electrolytes: Sodium (Na+), Potassium (K+) and Chloride (Cl-).

Why is Serum Electrolyte done?

The Serum Electrolyte Test is performed:

·     As a part of a routine health checkup

·     To assess problems in the water and pH balance of the body

·     As a part of the checkup to diagnose kidney diseases

·     Upon the appearance of symptoms indicating neuromuscular conditions like muscular weakness, irregular heartbeats or cardiac arrhythmia, etc.

·     At regular intervals to monitor the progress of condition and treatment efficacy while undergoing treatment for hypertension, kidney diseases, and metabolic acidosis

·     To monitor patients who are receiving diuretic therapy, intravenous fluids, or dialysis

What does Serum Electrolyte Measure?

The serum electrolyte test measures the following electrolytes:

  • Sodium (Na+)

  • Potassium (K+)

  • Chloride (Cl-)

Electrolytes play an important role in a number of body functions like metabolism, neuromuscular functioning, maintaining hydration and pH (acid-base balance). Electrolytes also help in the entry of nutrients into the cells and removal of waste products from the cells. Electrolytes carry an electrical charge, either negative or positive and exist as dissolved salts in blood and body tissues. The Serum Electrolyte test measures the following important electrolytes:

Sodium (Na+)

Sodium is an essential body electrolyte which, along with potassium, chloride, bicarbonate, etc., helps to maintain the normal fluid and pH balance of the body. It is also vital for cellular metabolism, and in the activity of nerves and muscles and transmission of impulses between them. Sodium is present in all the body fluids. The highest concentration of sodium is found in blood and extracellular fluid.

Sodium is supplied to the body principally through dietary salt (sodium chloride or NaCl), and a small portion of sodium is absorbed through other food items. The required portion is absorbed by the body and the remaining is excreted by the kidneys through urine. The body maintains a very narrow range of sodium concentration by three mechanisms:

·         Secretion of hormones natriuretic peptides and aldosterone to control sodium elimination through urine

·         Secretion of antidiuretic hormone (ADH), also called Vasopressin, to control the volume of water eliminated through urine

·         Induction of thirst

Any disruption in the above mentioned mechanisms gives rise to an imbalance in the concentration of sodium in the blood to produce Hyponatremia (low blood sodium concentration), or Hypernatremia (high blood sodium concentration). Both these conditions produce a number of symptoms and may even lead to death.

Potassium (K+)

Potassium is one of the essential body electrolytes along with sodium, chloride, bicarbonate, etc. As an electrolyte, potassium helps to regulate the amount of fluids present in the body and to maintain a correct pH balance. It performs a vital role in cellular metabolism and transport of nutrients and waste products in and out of cells. It is also essential in the transmission of nerve impulses to muscles and muscle activity.

Sufficient amount of potassium required by the body is absorbed from dietary sources, and the remaining unabsorbed potassium is excreted by the kidneys. The hormone called aldosterone maintains the body potassium level within a small normal range. Aldosterone acts on the nephrons present in the kidneys and activates a sodium-potassium pump which helps the body to reabsorb sodium and excrete potassium. This helps to maintain the potassium concentration in the blood within its normal range. Deviation of potassium concentration from its normal range gives rise to Hyperkalemia (high potassium level in blood), or Hypokalemia (low potassium level in blood). Both these conditions may produce a number of symptoms, and may even be fatal if not controlled.

Chloride (Cl-)

Chloride is an essential mineral which acts as an electrolyte along with potassium, sodium, bicarbonate, etc. It helps to maintain the normal fluid and electrolyte balance in the body. It also acts as a buffer to help maintain the pH balance of the body. It also plays essential roles in metabolism. Chloride is used by the stomach to produce hydrochloric acid (HCl) for digestion. Chloride is present in every body fluid. The highest concentration of chloride is found in blood and extracellular fluid (fluid present outside the cells).

Most of the chloride is supplied to the body through dietary salt (sodium chloride or NaCl), and a small portion is absorbed through other food items. The required portion is absorbed by the body and the remaining is excreted by the kidneys through urine. The concentration of chloride in blood is maintained within a very narrow range by the body. Its increase or decrease is directly correlated with the sodium levels.

Preparation for Serum Electrolyte

  • No special preparation required

Sample Type for Serum Electrolyte

The sample type collected for Serum Electrolyte is: Blood

Interpreting Serum Electrolyte results


The normal range of serum electrolytes may vary from lab to lab.

Sodium (Na+)

Normal range: 135 to 145 mmol/L

Hyponatremia: Below 135 mmol/L

Hypernatremia: Above 145 mmol/L

Sodium concentration in the body is maintained within a narrow normal range between 135 mmol/L and 145 mmol/L.

Hyponatremia or low blood sodium indicates that sodium concentration lies below the normal range.

Hypernatremia or high blood sodium indicates that sodium concentration lies above the normal range.

Potassium (K+)

Normal range: 3.5 to 5.0mmol/L (136.5 to 195μg/ml approx.)

Hypokalemia: Below 3.5mmol/L (Less than 136.5μg/ml approx.)

Hyperkalemia: Above 5.0mmol/L (Above 195μg/ml approx.)

Potassium concentration in the body is maintained within a narrow normal range between 3.5mmol/L and 5.0mmol/L.

Hypokalemia or low blood potassium indicates that potassium concentration lies below the normal range.

Hyperkalemia or high blood potassium indicates that potassium concentration lies above the normal range.

Chloride (Cl-)

Normal reference range:

  • Adults: 98 to 106 mEq/L (milliequivalents per liter)

  • Children: 90 to 110 mEq/L

  • Newborn: 96 to 106 mEq/L


Higher than normal chloride level is called Hyperchloremia.

Lower than normal chloride level is called Hypochloremia.

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Serum Electrolyte

Frequently Asked Questions about Serum Electrolyte

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. Is there any preparation required before the test?
Inform the doctor about the medications you may be taking. No other specific preparations are usually required before this test.
Q. What is Hyponatremia?
Hyponatremia is a condition where the blood sodium levels are below the normal range. This may occur due to: · Increased loss of sodium with body fluids due to conditions such as excessive sweating, vomiting, diarrhea, diuretics, or kidney diseases · Overconsumption of water, as common during strenuous exercise · Addison’s Disease · Ketonuria · Excess fluid accumulation due to heart failure, liver cirrhosis, or kidney diseases · Improper and overproduction of antidiuretic hormone or ADH
Q. What are the symptoms of Hyponatremia?
Symptoms of Hyponatremia include: · Fatigue · Drowsiness and confusion · Restlessness and irritability · Muscular weakness, twitching, or cramps · Nausea and vomiting · Headache · Seizures · Coma
Q. What is Hypernatremia?
Hypernatremia is the condition where blood sodium levels rise higher than the normal range. This may occur due to: · Insufficient consumption of water · Increase in loss of body fluids due to diarrhea, excessive sweating, extensive burns, or diuretics · Hyperaldosteronism · Cushing's syndrome · Excess water loss from kidneys due to Diabetes Insipidus · Excessive consumption of dietary salt or sodium bicarbonate · Certain medications
Q. What are the symptoms of Hypernatremia?
Symptoms of Hypernatremia include: · Excessive thirst · Drying up of mucous membranes · Low urine production · Muscle twitching and cramping · Agitation and restlessness · Irrational behavior · Convulsions and seizures · Coma
Q. What is Hypokalemia?
Hypokalemia is a condition where the blood potassium levels are below the normal range. This may occur due to: · Low dietary potassium · Chronic vomiting and diarrhea · Kidney diseases · Hyperaldosteronism or excess production of hormone aldosterone · Acetaminophen overdose · Insulin in diabetics, especially if the condition is poorly managed · Eating disorders like anorexia · Diuretic therapy · Certain medications like corticosteroids, some antibiotic and antifungal agents, and laxatives · Cushing’s syndrome
Q. What are the symptoms of Hypokalemia?
Symptoms of Hypokalemia include: · Fatigue · Palpitations · A tingling sensation or feeling of numbness · Constipation · Muscle weakness or spasms which may lead to muscle damage · Feeling lightheaded or dizzy · Irregular heartbeat or cardiac arrhythmia
Q. What is Hypochloremia?
Hypochloremia is a condition where the blood chloride levels are below the normal range. This may occur due to: · Kidney diseases · Congestive heart failure · Body fluid loss due to vomiting or diarrhea · Lung diseases like Chronic Obstructive Pulmonary Disease (COPD) · Diseases of adrenal gland like Addison’s disease, Cushing's syndrome, etc. · Metabolic alkalosis (high blood pH) · Drugs like diuretics, corticosteroids, or laxatives · Alcoholism
Q. What are the symptoms of Hypochloremia?
Symptoms of Hypochloremia include: · Rapid fluid loss · Dehydration · Fatigue and weakness · Breathing difficulty · Vomiting and diarrhea
Q. What is Hyperchloremia?
Hyperchloremia is the condition where blood chloride levels rise higher than the normal range. This may occur due to: · Kidney diseases · Excess saline in blood, as during intravenous saline administration in hospital · Excess consumption of salt in diet · Severe diarrhea · Dehydration · Hyperparathyroidism (over-secretion of parathyroid gland hormones) · Acute or Chronic Kidney Disease · Bromide poisoning · Metabolic acidosis (low blood pH) · Respiratory alkalosis · Certain medications like carbonic anhydrase inhibitors, laxatives, etc.
Q. What are the symptoms of Hyperchloremia?
Symptoms of Hyperchloremia include: · Fatigue · Muscular weakness · Excessive thirst · Dry mucous membranes like the mouth · Hypertension (high blood pressure)
Q. What factors can affect the results of Serum Electrolyte test?
The test results can be affected by the amount of fluid intake (e.g. drinking a lot of water) and fluid loss from the body (e.g. diarrhoea, vomiting, sweating). Certain medications may also affect the results (e.g. ACE inhibitors, beta blockers, angiotensin II receptor blockers (ARBs), and some diuretics, etc. which are used to lower blood pressure). False results may appear in the potassium test due to improper collection and handling of the blood specimen. If you clench and relax your fist too much during specimen collection, it might elevate the potassium level in your blood sample. Rough handling of the collected specimen or delay of the specimen in reaching the lab may cause potassium to leak out of the blood cells into the serum which will show falsely increased levels.
Q. What additional tests can be prescribed by your doctor in case the result of Serum Electrolyte test is not normal?
Additional tests that may be prescribed in case of abnormal Electrolyte test result are: · Urine Chloride Test · Urine Sodium Test · Urine Potassium Test · Urinalysis · Kidney Function Test · Blood Sugar Tests · Liver Function Test · Blood Phosphate Test · Electrocardiogram (ECG)
+ more

Tests Included in Serum Electrolyte(3 tests)

  • Potassium
  • Chloride
  • Sodium

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About SRL Limited

For over a hundred years, human pathology has been one of the keystones of medicine and rightly so at SRL, we offer our patients world-class Pathology services because their well-being is of the utmost importance to us. Pathology is quite simply the scientific study of the overall response of your body to any foreign influence, i.e., disease. Actually, we use this knowledge to diagnose & subsequently treat your ailment. What we basically do is carefully compare the normal structure and function of a human body (anatomy and physiology) to the abnormal structure and function we witness in an unwell human. Doing this is the most crucial phase & we take note of even the minutest details while adjudging the extent of your ailment because one slip can lead to an incorrect diagnosis, posing serious threat to your health. Our experts ensure that they are extremely careful while analyzing the samples. This is where our advanced technology chips in. SRL is proud to host state-of-the-art equipments based on the latest technology for a speedy and accurate result. We do not take any chances whatsoever with your health & well-being. Avail our Pathology services with no hesitation. You are always in good hands with SRL.

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