Bicarbonate (HCO3-)

Clinical definition of the Bicarbonate test
Bicarbonate is a chemical substance that acts as a buffer and does not allow the pH of the blood to become too acidic or too basic. The kidney and lungs balance the levels of bicarbonate in the body. If bicarbonate levels are too high or low, it might indicate a problem with those organs. Thus the bicarbonate test is helpful in detecting a number of conditions that affect the blood bicarbonate levels such as lung disease, kidney disorders and metabolic conditions.

Why is the Bicarbonate test done?
The bicarbonate test is performed to measure the level of bicarbonate in a person's blood.
It may be done under the following conditions:-

  • As part of a routine exam or to help evaluate a chronic or acute illness
  • To detect and evaluate an electrolyte imbalance
  • To monitor the effectiveness of treatment for known imbalances
  • At different intervals to help monitor conditions, such as kidney disease and hypertension
  • To evaluate your body’s acid-base balance (pH)
  • As a part of the Electrolyte panel along with other tests like such as sodium, potassium and chloride test

What are the common signs/symptoms when the Bicarbonate test is done?

  • Weakness
  • Confusion
  • Prolonged vomiting
  • Water retention
  • Dehydration
  • Respiratory distress

Who should do the Bicarbonate test (Target population)?
Persons showing the above signs & symptoms or those having a problem of electrolyte imbalance.

What should I do before the Bicarbonate test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *


(Blood Sample)


(Collection of blood from a vein, usually from the arm)

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my Bicarbonate test results?

Reference Range*


23 to 29 MEq/L **


** Milliequivalent per liter
Inference: Higher values are found in the blood of persons suffering from persistent vomiting and dehydration or in those who have just undergone a blood transfusion. The excessive use of antacids can also increase the bicarbonate level. It can also be indicative of conditions like Chronic Obstructive Pulmonary Disease, heart disease, Cushing's disease and Conn's syndrome. Low bicarbonate values are observed due to rapid breathing and an overdose of alcohol or aspirin. Severe malnutrition, burns, shock, liver or kidney diseases, hyperthyroidism, uncontrolled diabetes, or a massive heart attack can also lower the bicarbonate value.
‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the Bicarbonate test

Lower-than-normal levels may be due to:

  • Addison disease
  • Kidney disease
  • Lactic acidosis
  • Metabolic acidosis
  • Methanol poisoning
  • Chronic diarrhea
  • Diabetic ketoacidosis
  • Ethylene glycol or methanol poisoning
  • Salicylate toxicity (aspirin overdose)

Higher-than-normal levels may be due to:

  • Breathing disorders
  • Cushing syndrome
  • Excessive vomiting
  • Hyperaldosteronism
  • Lung diseases
  • Conn’s syndrome
  • Metabolic alkalosis

The following conditions may also alter bicarbonate levels:

  • Alkalosis
  • Delirium
  • Dementia
  • Renal tubular acidosis; distal
  • Renal tubular acidosis; proximal

Other tests related to the Bicarbonate test

  • Electrolyte panel
  • Sodium
  • Potassium
  • Chloride
  • CMP
  • BMP
  • Blood gases

Synonyms : Total Carbon dioxide (TCO2)
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