Bicarbonate blood test: CO2 levels, normal range and price

A bicarbonate blood test, also called a CO2 blood test or total CO2, measures the carbon dioxide carried in your blood, most of which travels as bicarbonate. Bicarbonate is the buffer that keeps blood from turning acidic, so the result is a window on the body's acid-base balance and on the kidneys and lungs that hold it steady. It is part of the standard electrolyte set and is read with sodium, potassium and chloride.

What it measures

Cells make carbon dioxide as a waste product, and the blood carries it to the lungs to be breathed out. Most of the carbon dioxide in blood is in the form of bicarbonate (HCO3), so although a report may print the result as CO2, what it mainly reflects is bicarbonate. It is not a measure of the gas you breathe out.

Two organs set the level. The lungs control how much carbon dioxide is breathed off. The kidneys reclaim bicarbonate from the urine they make and get rid of acid, partly by producing ammonia to carry it out. When one of these systems is under strain, the other often shifts to compensate, which is why bicarbonate can move for reasons that start in the lungs as well as in the kidneys or the gut.

Normal range

A typical adult reference range is 23 to 29 mmol/L, the same as 23 to 29 mEq/L. Ranges vary by laboratory, method, age and sex, so read your result against the range printed on your own report.

In chronic kidney disease, a bicarbonate of 22 mmol/L or below is the usual threshold for calling it a metabolic acidosis.

What a low bicarbonate usually points to

A low result most often means the body is handling extra acid, a metabolic acidosis, and bicarbonate has been used up buffering it, or that bicarbonate is being lost.

• Kidney disease. As kidney function falls, the kidneys reclaim less bicarbonate and clear less acid. In one large US cohort of people with chronic kidney disease, a low bicarbonate was found in about 7% at stage 2, 13% at stage 3 and 37% at stage 4.
• Diarrhoea that goes on for a long time, a cause of metabolic acidosis that starts in the gut rather than the kidneys.
• A build-up of acid, as in diabetic ketoacidosis, lactic acidosis or poisoning with large amounts of aspirin.
• Breathing faster than the body needs (hyperventilation) over a period, where the kidneys let bicarbonate fall to compensate.
• Addison disease, in which the adrenal glands make too little hormone.

What a doctor typically looks at next is sodium and chloride, to work out the anion gap: sodium minus the sum of chloride and bicarbonate. A raised gap and a normal gap point towards different groups of causes. A normal gap with a raised chloride is the pattern seen with diarrhoea and with disorders of the kidney tubules. Kidney function, through creatinine and eGFR, usually comes next, and where a low reading has no clear explanation a blood gas sample can show whether the low bicarbonate is real.

What a high bicarbonate usually points to

• Prolonged vomiting or dehydration, which push the blood towards the alkaline side (a metabolic alkalosis).
• Lung disease that retains carbon dioxide, where bicarbonate rises to compensate.
• Hormone conditions with too much aldosterone (hyperaldosteronism) or too much cortisol (Cushing syndrome).
• Some medicines, both prescription and over the counter, which is why the medicine list matters when the result is read.

Next, a doctor typically reads chloride beside it, since chloride tends to fall as bicarbonate rises, and asks about vomiting, fluid intake and medicines.

What moves bicarbonate

• How full the tube is. Bicarbonate depends on the sample tube being filled properly. In a study of emergency department patients, average bicarbonate was 21.7 mmol/L when a 10 mL tube was full, 19.4 mmol/L with 3 mL in it and 16.3 mmol/L with 1 mL, a fall large enough to look like an acidosis that was not there. A second study saw the same fall whether samples were analysed 10 or 40 minutes after collection.
• Unusual blood fats or proteins. Very high triglycerides, or abnormal proteins called paraproteins, can interfere with some measurement methods and give a falsely low reading.
• The tourniquet. Venous stasis from a tourniquet is one of the reasons a serum bicarbonate and a blood gas bicarbonate can differ.
• Illness. Vomiting, diarrhoea and dehydration move it in the directions above.
• Medicines. Several can raise or lower it.

Preparing for the test

Bicarbonate itself needs no special preparation. If other tests are taken from the same sample you may be asked to fast for several hours. Tell the person taking the sample about all your medicines, including ones bought without a prescription, and about any recent vomiting or diarrhoea. Because an underfilled tube lowers the result, an unexplained low reading is worth discussing with a doctor, who may simply repeat it.

How Clare's panel handles it

In Clare's panel, bicarbonate / total CO2 is measured by the lab, together with sodium, potassium and chloride, so a doctor can work out the anion gap from a single report. When Clare opens, each result will sit in one health account beside your earlier ones, with plain explanations in English and Arabic.

Price in the UAE

Bicarbonate is not usually sold on its own; it comes within a kidney function test or an electrolyte set. When we read public prices on 11 October 2026, a kidney function test cost from 89 to 900 at 6 UAE providers. VAT is rarely stated, some are offer prices or starting prices, and home collection can add a fee. Packages differ in what they include, and not every kidney function test lists bicarbonate, so check the marker list before buying.

Related tests

Bicarbonate is read with chloride, its partner in the acid-base balance, and with sodium and potassium, the rest of the electrolyte set. Because the kidneys hold bicarbonate steady, creatinine and eGFR, also part of the kidney function test, add how well they are filtering. Comprehensive blood test in Dubai: what to expect explains where electrolytes sit in a full panel.

Why the number means more over time

One bicarbonate reading can be thrown by a bout of vomiting, a poorly filled tube or a recent illness. Several readings, taken the same way, show where the level really sits. In chronic kidney disease bicarbonate is followed over time, because a gradual fall tracks the kidneys' growing difficulty clearing acid. If your result is outside the range, or drifting from one test to the next, talk to a doctor about it with the results in front of you. Clare is opening with a waitlist at clare.health.