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Bicarbonate (HCO₃⁻) concentration in serum/plasma

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of bicarbonate, a key chemical in your blood that helps balance acidity and alkalinity. It’s often checked when your doctor suspects acid-base imbalances.

Quick summary

["Bicarbonate helps regulate your body’s pH and can signal acid-base disorders."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
1963-8
Short code
HCO3 SerPl-sCnc
Synonyms
HCO3 SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
28
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Does This Test Measure?

Bicarbonate is a critical buffer in your blood, helping maintain a stable pH level. Your body produces bicarbonate naturally, and levels can be affected by conditions like kidney disease, metabolic disorders, or respiratory issues. This test helps doctors assess whether your body is too acidic (acidosis) or too alkaline (alkalosis).

Why Might Your Doctor Order This Test?

Your doctor may request this test if you have symptoms like shortness of breath, fatigue, nausea, or muscle cramps. It’s also used to monitor conditions like kidney disease, diabetes, or heart problems that can disrupt bicarbonate levels. Sometimes, it’s part of broader tests to check acid-base balance in your blood.

How Is This Test Done?

A small blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure bicarbonate concentration. The test typically takes a few minutes to complete, and results are usually available within 24–48 hours.

What Are Possible Results?

Results are reported in milliequivalents per liter (mEq/L), but exact reference ranges can vary by lab. Low bicarbonate levels may indicate metabolic acidosis, while high levels could suggest metabolic alkalosis. Your doctor will interpret results in the context of your overall health and symptoms.

Reference range

NCBI: HCO3- 22-28 mmol/LN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum bicarbonate

Frequently asked questions

What Causes Changes in Bicarbonate Levels?
Bicarbonate levels can drop due to conditions like diabetic ketoacidosis, severe dehydration, or kidney problems that fail to excrete acid properly. High bicarbonate levels may occur in conditions like vomiting, excessive antacid use, or certain kidney disorders. Chronic respiratory issues (like COPD) can also affect bicarbonate indirectly.
How Does This Test Help Diagnose Conditions?
This test is part of a broader evaluation for acid-base imbalances. When combined with other tests (like blood pH or CO₂ levels), it helps doctors diagnose conditions like metabolic acidosis or alkalosis. For example, low bicarbonate with low pH suggests metabolic acidosis, while high bicarbonate with high pH may indicate metabolic alkalosis.
What Should I Expect Before or After the Test?
No special preparation is needed for this test, but inform your doctor about any medications you’re taking, especially diuretics, antacids, or acid-lowering drugs. After the blood draw, you may feel slight discomfort, but it’s usually temporary. If you have a bleeding disorder or severe anemia, let your doctor know before the test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy