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Electrolytes
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This test reports the anion gap calculated from a blood gas sample using chloride, together with other electrolytes measured by the analyzer. The anion gap estimates the difference between measured positive and negative ions, which reflects the amount of unmeasured acids and anions in your blood.
It is performed on whole blood, often arterial or venous, and is commonly used in urgent or critical care settings. Because it is chloride based and derived on a blood gas analyzer, results may differ slightly from a standard chemistry panel done on serum or plasma.
Clinicians use the anion gap to help identify metabolic acidosis and to sort through causes of acid base problems. A raised gap can point toward conditions like kidney dysfunction, diabetic ketoacidosis, lactic acidosis, or ingestion of certain toxins.
This test is often ordered with a blood gas to assess acidity, carbon dioxide, and bicarbonate during acute illness, surgery, or when breathing or circulation problems are suspected. The chloride based calculation provides rapid bedside guidance that can influence fluids, ventilation, and medication choices.
Albumin and other proteins contribute to the baseline anion gap. When albumin is low, the expected gap narrows, so your care team may adjust interpretation to your protein level or confirm with a serum chemistry panel.
A higher anion gap suggests there are additional acids or unmeasured anions in your blood. This pattern can occur in several illnesses and usually improves as the underlying problem is treated. A normal anion gap with acidosis points to other mechanisms, such as bicarbonate loss or shifts in chloride.
A lower than expected anion gap is uncommon and may reflect low albumin, laboratory interference, or rarely an excess of certain positively charged proteins. Because different instruments and formulas exist, your result can vary between care settings.
Interpreting this test works best alongside your symptoms, blood gas values, electrolytes, kidney function, and medication history. If a result is unexpected, your clinician may repeat the test, check a standard chemistry panel, review albumin, or look for causes such as toxins or dehydration.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Arterial and venous blood can yield slightly different results, and delays to analysis allow gas exchange that can shift bicarbonate and influence the calculation.
Point of care blood gas analyzers may use different chloride electrodes and formulas than central laboratories, leading to small but meaningful differences.
Low albumin lowers the expected anion gap. Malnutrition, liver disease, inflammation, or pregnancy related changes can alter interpretation.
Salicylates, methanol, ethylene glycol, or metformin in kidney impairment can raise the gap. Halides like bromide can falsely affect chloride and make the gap appear low.
Poor circulation, sepsis, or seizures can increase lactate and raise the gap, while gastrointestinal bicarbonate loss can cause acidosis without raising the gap.
Whole blood on a blood gas analyzer can differ from serum or plasma on a chemistry analyzer, so cross checks may be needed when results do not match the clinical picture.
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