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As part of an electrolyte panel or metabolic panel to identify or monitor an electrolyte imbalance or acid-base (pH) imbalance
During a routine health exam or as recommended by your healthcare practitioner if you are experiencing symptoms such as weakness, confusion, prolonged vomiting, or breathing problems that could indicate an electrolyte imbalance or an acid-base imbalance (acidosis or alkalosis)
A blood sample drawn from a vein
Bicarbonate is an electrolyte, a negatively charged ion that is used by the body to help maintain the body's acid-base (pH) balance. It also works with the other electrolytes (sodium, potassium, and chloride) to maintain electrical neutrality at the cellular level. This test measures the total amount of carbon dioxide (CO2) in the blood, which occurs mostly in the form of bicarbonate (HCO3-). The CO2 is mainly a by-product of various metabolic processes.
Measuring bicarbonate as part of an electrolyte or metabolic panel may help diagnose an electrolyte imbalance or acidosis or alkalosis. Acidosis and alkalosis describe the abnormal conditions that result from an imbalance in the pH of the blood caused by an excess of acid or alkali (base). This imbalance is typically caused by some underlying condition or disease.
The lungs and kidneys are the major organs involved in regulating blood pH through the removal of excess bicarbonate.
Any disease or condition that affects the lungs, kidneys, metabolism, or breathing has the potential to cause acidosis or alkalosis.
The bicarbonate test gives a healthcare practitioner a rough estimate of your acid-base balance. This is usually sufficient, but measurements of gases dissolved in the blood (blood gases) may be done if more information is needed. Bicarbonate is typically measured along with sodium, potassium, and possibly chloride in an electrolyte panel as it is the balance of these molecules that gives the healthcare practitioner the most information.
The bicarbonate (or total CO2) test is usually ordered along with sodium, potassium, and chloride as part of an electrolyte panel, which is included in a basic metabolic panel (BMP) and a comprehensive metabolic panel (CMP). A calculated bicarbonate level might also be reported as part of a blood gas panel.
The electrolyte panel may be used to help detect, evaluate, and monitor electrolyte imbalances and/or acid-base (pH) imbalances (acidosis or alkalosis). The tests may be used as part of a routine health exam or to help evaluate and monitor a variety of chronic or acute illnesses, such as:
When acidosis or alkalosis is identified, bicarbonate tests and blood gases may be ordered to evaluate the severity of the pH imbalance. These tests help determine whether it is primarily respiratory (due to an imbalance between the amount of oxygen coming in and CO2 being released) or metabolic (due to imbalance in the amount of acid produced by the body or ability of the kidneys to remove acid from the body). They also help monitor treatment until acid-base balance is restored.
Bicarbonate testing may be ordered when you have a routine health checkup.
This testing may also be ordered when acidosis or alkalosis is suspected or when you have an acute condition with symptoms such as:
Electrolytes may be ordered at regular intervals when you have a disease or condition or are taking a medication that can cause an electrolyte imbalance.
Bicarbonate levels are typically interpreted along with results from other tests done at the same time, such as the other electrolytes.
A bicarbonate level that is higher or lower than normal may mean that the body is having trouble maintaining its acid-base balance, either by failing to remove carbon dioxide through the lungs or the kidneys or perhaps because of an electrolyte imbalance, particularly a deficiency of potassium. Both of these imbalances may be due to a wide range of conditions.
Examples of conditions that can cause a low bicarbonate level include:
Examples of conditions that can cause a high bicarbonate level include:
Your bicarbonate result is interpreted by your healthcare practitioner within the context of other tests that you have had done as well as other factors, such as your medical history. A single high or low result may or may not have medical significance. Generally, this is the case when the test value is only slightly higher or lower than the reference range. This is why healthcare practitioners may repeat a test on you and why they may look at results from prior times when you had the same test performed.
On the other hand, a result outside the range may indicate a problem and warrant further investigation. Your healthcare practitioner will evaluate your test results and determine whether a result that falls outside of the reference range means something significant for you.
Blood gas tests, in which blood is drawn from an artery instead of a vein, can give your healthcare practitioner more information about your acid-base balance. They can tell your provider whether your lungs are working properly to keep oxygen and carbon dioxide at healthy levels.
If your bicarbonate is high or low, your healthcare practitioner will identify and treat the underlying cause. For example, high bicarbonate may be caused by emphysema, which may be treated with oxygen therapy and medications, or by severe diarrhea or vomiting, which would be addressed by treating the cause of the diarrhea or vomiting. Low bicarbonate may be caused by diabetic ketoacidosis, for example, which can be addressed in part by fluid and electrolyte replacement and insulin therapy.
Some drugs may increase bicarbonate levels including fludrocortisone, barbiturates, bicarbonates, hydrocortisone, loop diuretics, and steroids.
Drugs that may decrease bicarbonate levels include methicillin, nitrofurantoin, tetracycline, thiazide diuretics, triamterene, calcium inhibitors, anti-viral/HIV drugs, and valproic acid.
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