Bicarbonate is almost always requested as part of an electrolyte panel/profile.  In the first instance, the bicarbonate result informs your doctor about the likely acid-base status of the blood.  When taken into consideration with the other electrolyte results, it is often possible to diagnose more specific types of acid-base balance disturbance.
 

Some of the most common reasons to measure bicarbonate include the following:

• As part of a routine health check.
• If you are at risk of an acid-base disturbance (e.g. if you are taking medications known to affect bicarbonate levels in the body).
• If you have symptoms of an acid-base or electrolyte imbalance (there are many such symptoms, your doctor will be best placed to advise on this).

Bicarbonate results above the reference interval usually mean that your body is either losing too much acid, the lungs are failing to get rid of unwanted CO2, or that the kidneys are not getting rid of excess bicarbonate.  Common causes of a high bicarbonate include:

• A chronic lung disease such as COPD
• Prolonged vomiting
• Use of certain drugs such as diuretics

Bicarbonate results that are below the reference interval usually indicate the build-up of acid in the blood (acidosis).  Common causes of a low bicarbonate include:

• Chronic kidney disease
• Poorly-controlled diabetes
• Chronic, severe diarrhoea
• Severe infection (sepsis)

Adult

22-32 mmol/L

Paediatric

0 to <1 week             15-28mmol/L
1 week - 2 years       16-29 mmol/L
2 years - 10 years     17-30 mmol/L
10 years - 18 years   20-32 mmol/L

The reference intervals shown above are known as a harmonised reference intervals. This means that eventually all laboratories in Australia should use the same interval so that wherever your sample is tested, the reference interval should be the one shown above. Laboratories are in the process of adopting these harmonised intervals so it is possible that the intervals shown on the report of your results for this test may be slightly different until this change is fully adopted. More information can be found under Reference Intervals – An Overview.
 

Some drugs may increase bicarbonate levels such as diuretics e.g. frusemide or Lasix. Often other electrolytes will also be low e.g. sodium, potassium. Similarly some drugs may cause slightly low bicarbonate levels. Your doctor can advise if this appears to be a problem.

Occasionally a low bicarbonate may occur due to a laboratory error.  This is most common if there has been a prolonged delay between collecting the sample and analysis in the laboratory, or if the specimen tube was uncapped before being analysed.  Your doctor can discuss any such cases with the laboratory directly.
 

If your bicarbonate is high or low, your doctor 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 diarrhoea or vomiting (which would be treated by treating the reason for the diarrhoea or vomiting). Low bicarbonate may be caused by diabetic ketoacidosis, which can be treated in part by treating the blood sugar problem that led to the ketoacidosis or kidney diseases.

Oxygen, both dissolved and bound to haemoglobin, is vital to the functioning of all cells in the body. Smokers and people who have been exposed to carbon monoxide may have measurable amounts of it in their blood. Carbon monoxide also binds to haemoglobin, diminishing your body's ability to carry oxygen. Nitrogen, from air, is dissolved in blood at low concentrations but is usually not of any significance.

Blood gas tests, in which blood is drawn from an artery instead of a vein, can give your doctor a more accurate assessment of the body's pH (acid/base status) and indicate whether your body is taking in enough oxygen and getting rid of enough CO₂.