Bicarbonate

A bicarbonate level is almost always done along with other electrolytes to tell your doctor whether your sodium, potassium, chloride and bicarbonate levels are in balance. They may be measured as part of routine blood testing or when your doctor suspects an imbalance. Bicarbonate may also be measured when your doctor is evaluating your acid-base balance, to screen for an imbalance, and to monitor a known problem during treatment.

Bicarbonate testing may be requested, usually as part of an electrolyte profile when:

• you are having a routine blood test
• your doctor suspects that you may be retaining water or are dehydrated, upsetting your electrolyte balance
• to help evaluate your body's acid-base balance (pH)
• to monitor a condition or treatment that might cause an electrolyte imbalance.

When bicarbonate levels are higher than normal, it suggests that your body is having trouble maintaining its pH balance either by failing to remove carbon dioxide or perhaps because of an electrolyte imbalance, particularly a deficiency of potassium. Both of these imbalances may be due to a wide range of dysfunctions. Bicarbonate elevations may be seen with severe vomiting, chronic lung-related problems, such as emphysema, and some hormonal disorders such as Cushings disease.

Low bicarbonate levels may be seen with chronic diarrhoea, diabetic ketoacidosis and kidney failure.

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 interval. This means that eventually all laboratories in Australia will eventually use this same interval so 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 especially diuretics such as frusemide (usually as a consequence of potassium deficiency). Other drugs may cause slightly low levels. Your doctor can advise if this appears to be a problem.

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 your red blood cells, diminishing your body's ability to carry oxygen. Nitrogen, from air, is dissolved in blood at low concentrations but is not normally important in health care. An exception is the case of marine divers with decompression sickness (‘bends’).

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.